Examples of plant families that contain species that are safe for human consumption and species that are poisonous to humans?

I am trying to make a point to someone that just because two plants share a family and one plant is safe for human consumption, it does not follow that the other plant also is safe for human consumption. Can anyone provide an example I can use as proof?

The most classic example if you want to win this argument would be the family Solanaceae.

Also referred to as the Nightshade family, it includes the deadly nightshade or Atropa belladonna and many other plants not safe to eat.

Other members of the family are tomatoes, peppers, potatoes, and more.

Plant families can be massively diverse, and toxicity doesn't really have much relationship to family. Most of the compounds that are found in plants that are toxic are found in other non-toxic plants as well: dose is crucial.

The Apiaceae family has many edible plants including carrot, parsley, fennel, celery, and parsnip, and has toxic plants such as poison hemlock, fool's parsley, and giant hogweed.

Both the cashew and poison ivy are members of the Anacardiaceae family.

Fungi are not plants and you've tagged this as botany, so this is perhaps off-topic, but I feel like it might help you make your point: the genus Amanita contains extremely toxic species (A. phalloides), highly regarded edible ones (A. caesarea) as well as psychoactive ones (A. muscaria).

While all the other answers have described one plant family having both edible species as well as poisonous species, I am compiling all the families in one answer.

  1. Anacardiaceae

Mangos (Mangifera indica) and Cashews (Anacardium occidentale) belong to Anacardiaceae, and also the poisonous Sumacs (Rhus spp.).

  1. Apiaceae

Carrots (Daucus carrota), Parsnips (Pastinica sativa), Dill (Anethum graveolens) and the poisonous Poison Hemlock (Conium maculatum), and Water Hemlock (Cicuta spp.)

  1. Apocynaceae

Milkweed (Asclepias spp.) and the poisonous Dogbane (Apocynum spp.) is commonly known as the poisonous relative of Milkweed.

  1. Ranunculaceae

Marsh Marigold (Caltha palustrus) and the poisonous Buttercups (Ranunculus spp.)

  1. Solanaceae

Food crops like Potatoes and Tomatoes and deadly poisons like Deadly Nightshade (Atropa belladonna), Jimson Weed (Datura spp.) etc.



List of edible seeds

An edible seed [n 1] is a seed that is suitable for human or animal consumption. Of the six major plant parts, [n 2] seeds are the dominant source of human calories and protein. [1] A wide variety of plant species provide edible seeds most are angiosperms, while a few are gymnosperms. As a global food source, the most important edible seeds by weight are cereals, followed by legumes, nuts, [2] then spices.

Cereals and legumes correspond with the botanical families Poaceae and Fabaceae, respectively, while nuts, pseudocereals, and other seeds form polyphylic groups based on their culinary roles.

Are Small Quantities of Heavy Water Safe?

Just because heavy water isn't radioactive doesn't mean it's completely safe to drink. If you ingested enough heavy water, the biochemical reactions in your cells would be affected by the difference in the mass of the hydrogen atoms and how well they form hydrogen bonds.

You could consume a single glass of heavy water without suffering any major ill effects, however, should you drink any appreciable volume of it, you might begin to feel dizzy.   That's because the density difference between regular water and heavy water would alter the density of the fluid in your inner ear.

Department of Animal Science - Plants Poisonous to Livestock

Welcome to the Tannin webpage. We offer a variety of information on tannins including, but not limited to, their biosynthesis, chemical structures, toxicology, positive effects, chemical analysis.

Tannins are naturally occurring plant polyphenols . Their main characteristic is that they bind and precipitate proteins . They can have a large influence on the nutritive value of many foods eaten by humans and feedstuff eaten by animals. Tannins are common in fruits (grapes, persimmon, blueberry, etc.), in tea, in chocolate, in legume forages (trefoil, etc.), in legume trees ( Acacia spp., Sesbania spp., etc.), in grasses (sorghum, corn, etc.).

Tannins contribute to many aspects of our daily lives. They are responsible for the astringent taste we experience when we partake of wine or unripe fruits, and for the enchanting colors seen in flowers and in autumn leaves.

For more information on tannins explore the following topics:


The word tannin is very old and reflects a traditional technology. "Tanning" (waterproofing and preserving) was the word used to describe the process of transforming animal hides into leather by using plant extracts from different plant parts of different plant species.

  • Plant parts containing tannins include bark, wood, fruit, fruitpods, leaves, roots, and plant galls.
  • Examples of plant species used to obtain tannins for tanning purposes are wattle (Acacia sp.), oak (Quercus sp.), eucalyptus (Eucalyptus sp.), birch (Betula sp.), willow (Salix caprea), pine (Pinus sp.), quebracho (Scinopsis balansae) .

Tannins are phenolic compounds that precipitate proteins . They are composed of a very diverse group of oligomers and polymers. There is some confusion about the terminology used to identify or classify a substance as a tannin, In fact,

  • not only tannins bind and precipitate proteins (other phenolics such as pyrogallol and resorcinol also have this property),
  • not all polyphenols precipitate proteins or complex with polysaccharides.

One of the most satisfactory definition of tannins was given by Horvath (1981):

" Any phenolic compound of sufficiently high molecular weight containing sufficient hydroxyls and other suitable groups (i.e. carboxyls) to form effectively strong complexes with protein and other macromolecules under the particular environmental conditions being studied "


Tannins are widely distributed in the plant kingdom. They are common both in Gymnosperms and Angiosperms. Within Angiosperms, tannins are more common in Dicotyledons than in Monocotyledons.

  • Leguminosae : Acacia sp. (wattle) Sesbania sp. Lotus sp. (trefoil) Onobrychis sp. (sainfoin)
  • Anacardiaceae: Scinopsis balansae (quebracho)
  • Combretaceae : myrobalan
  • Rhizophoraceae : mangrove
  • Myrtaceae: Eucalyptus sp., Mirtus sp. (Myrtle)
  • Polinaceae : canaigre.

Other important tannin containing plants are Quercus sp. (oak), Acer sp. (maple), Betula sp. (birch), Salix caprea (willow), Pinus sp. (Pine), Sorghum sp.

Tannins are located mainly in the vacuoles or surface wax of the plants. In these sites they do not interfere with plant metabolism. Only after cell breakdown and death can they act and have metabolic effects.

  • Bud tissues - most common in the outer part of the bud, probably as protection against freezing
  • Leaf tissues - most common in the upper epidermis. However, in evergreen plants, tannins are evenly distributed in all leaf tissues. They serve to reduce palatability and, thus, protect against predators.
  • Root tissues - most common in the hypodermis (just below the suberized epidermis). They probably act as a chemical barrier to penetration and colonization of roots by plant pathogens.
  • Seed tissues - located mainly in a layer between the outer integument and the aleurone layer. They have been associated with the maintenance of plant dormancy, and have allelopathic and bactericidal properties.
  • Stem tissues - often found in the active growth areas of the trees, such as the secondary phloem and xylem and the layer between epidermis and cortex. Tannins may have a role in the growth regulation of these tissues. They are also found in the heartwood of conifers and may be a contribute to the natural durability of wood by inhibiting microbial activity.


There are three large classes of secondary metabolites in plants:

Tannins belong to the phenolics class. All phenolic compounds (primary and secondary) are, in one way or another, formed via the shikimic acid pathway , also known as the phenylpropanoid pathway.

The same pathway leads to the formation of other phenolics such as isoflavones , coumarins , lignins and aromatic aminoacids (tryptophan, phenylalanine and tyrosine).

The two main categories of tannins that impact animal nutrition are hydrolyzable tannins (Hts) and condensed tannins identified more correctly as proanthocyyanidins (Pas) that are resistant to hydrolytic degragation. An example of how several common tannins are formed is as follows:

  • Gallic acid is derived from quinic acid.
  • Ellagotannins are formed from hexahydroxydiphenic acid esters by the oxidative coupling of neighboring gallic acid units attached to a D-glucose core.
  • Further oxidative coupling forms the hydrolyzable tannin (HT) polymers.
  • Proanthocyanidin (PA) biosynthetic precursors are the leucocyanidins (flavan-3,4-diol and flavan-4-ol)
    • Upon autoxidation, in the absence of heat, they form anthocyanidin and 3-deoxyanthocianidin, which, in turn, polymerize to form PAs.

    Chemical Structure

    Tannins are one of the many types of secondary compounds found in plants
    Characteristics of tannins:

    • oligomeric compounds with multiple structure units with free phenolic groups ,
    • molecular weight ranging from 500 to >20,000,
    • soluble in water, with exception of some high molecular weight structures,
    • ability to bind proteins and form insoluble or soluble tannin-protein complexes.

    Tannins are usually subdivided into two groups:

    HTs are molecules with a polyol (generally D-glucose) as a central core. The hydroxyl groups of these carbohydrates are partially or totally esterified with phenolic groups like gallic acid (-->gallotannins) or ellagic acid (--> ellagitannins). HT are usually present in low amounts in plants.

    Some authors define two additional classes of hydrolyzable tannins: taragallotannins(gallic acid and quinic acid as the core) and caffetannins (caffeic acid and quinic acid)

    • The phenolic groups that esterify with the core are sometimes constituted by dimers or higher oligomers of gallic acid (each single monomer is called galloyl)
    • Each HT molecule is usually composed of a core of D-glucose and 6 to 9 galloyl groups
    • In nature, there is abundance of mono and di-galloyl esters of glucose (MW about 900). They are not considered to be tannins. At least 3 hydroxyl groups of the glucose must be esterified to exhibit a sufficiently strong binding capacity to be classified as a tannin.
    • The most famous source of gallotannins is tannic acid obtained from the twig galls of Rhus semialata . It has a penta galloyl-D-glucose core and five more units of galloyl linked to one of the galloyl of the core.
    • The phenolic groups consist of hexahydroxydiphenic acid , which spontaneously dehydrates to the lactone form, ellagic acid .
    • Molecular weight range: 2000-5000.
    • hydrolyzed by mild acids or mild bases to yield carbohydrate and phenolic acids
    • Under the same conditions, proanthocyanidins (condensed tannins) do not hydrolyze.
    • HTs are also hydrolyzed by hot water or enzymes (i.e. tannase).

    Proanthocyanidins (condensed tannins)

    PAs are more widely distributed than HTs. They are oligomers or polymers of flavonoid units (i.e. flavan-3-ol) linked by carbon-carbon bonds not susceptible to cleavage by hydrolysis.

    • PAs are more often called condensed tannins due to their condensed chemical structure. However, HTs also undergo condensation reaction. The term, condensed tannins, is therefore potentially confusing.
    • The term, proanthocyanidins, is derived from the acid catalyzed oxidation reaction that produces red anthocyanidins upon heating PAs in acidic alcohol solutions.
      • The most common anthocyanidins produced are cyanidin (flavan-3-ol, from procyanidin) and delphinidin (from prodelphinidin)

      Interaction with other Macromolecules

      Tannins have a major impact on animal nutrition because of their ability to form complexes with numerous types of molecules, including, but not limited to,

      • Carbohydrates,
      • Proteins,
      • Polysaccharides,
      • Bacterial cell membranes,
      • Enzymes involved in protein and carbohydrates digestion.

      Both starch and cellulose are complexed by tannins (especially by PAs):

      • Starch-tannin interaction - starch has the ability to form hydrophobic cavities that allow inclusion complexes with tannins and many other lipophyllic molecules. Only starch, among the molecules that are bound by tannins, has this embedding characteristic.
      • Cellulose-tannin interaction - cellulose has a direct surface interaction with tannins.
      • Cell wall carbohydrate-tannin interaction - this association is less understood. One explanation is that tannins associate with plant cell walls in a manner reminiscent to that of lignin. However, another explanation is that this association is merely an artifact of tannin isolation from non-living cells. Indeed, the location of tannins and cell wall carbohydrates is quite different in living cells than in plant cells after digestion by animals.
      • Tannin-carbohydrate interactions are increased by carbohydrates with high molecular weight, low solubility and conformational flexibility. These interactions are probably based on hydrophobic and hydrogen linkages.

      The capacity of tannins to bind proteins has been recognized for centuries. Leather tanning is a very ancient practice. Tannin-protein interactions are specific and depend on the structure of both the protein and tannin.

      • Protein characteristics that favor strong bonding
        • large molecular size,
        • open and flexible structures,
        • richness in proline.
        • high molecular weight,
        • high conformational mobility.
        • The tannin's phenolic group is an excellent hydrogen donor that forms strong hydrogen bonds with the protein's carboxyl group.
          • For this reason, tannins have a greater affinity to proteins than to starch.
          • autoxidation over time, or
          • action of oxidative enzymes (i.e. polyphenoloxydases and peroxidases). Covalent bonding is far more difficult to disrupt than the previous types of bonding and is nutritionally very important because of its irreversible nature.
          • In solution at high pH, phenolic hydroxyls are ionized and proteins have net negative charges. Under these conditions, precipitation does not occur because proteins exhibit repulsive forces.
          • Soluble complexes are favored when protein concentration is in excess (fewer tannin attachment sites per each protein molecule). Soluble complexes represent an analytical problem because they do not precipitate and, thus, are difficult to measure.
          • Insoluble complexes are formed when tannins are present in excess and form an hydrophobic outer layer in the complex surface.

          Nutritional Effects: toxic and antinutritional effects

          Tannins act as a defense mechanism in plants against pathogens, herbivores and hostile environmental conditions. Generally, tannins induce a negative response when consumed. These effects can be instantaneous like astrigency or a bitter or unpleasant taste or can have a delayed response related to antinutritional/toxic effects.

          This section will cover the effect of tannins on:

          Tannins negatively affect an animal's feed intake, feed digestibility, and efficiency of production. These effects vary depending on the content and type of tannin ingested and on the animal's tolerance , which in turn is dependent on characteristics such as type of digestive tract, feeding behavior, body size, and detoxification mechanisms.

          Sites of action of tannins :

          • Oral cavity - mastication ruptures the plant cell tissue and exposes proteins and carbohydrates to tannins.
          • Rumen and gastrointestinal tract lumen - unbound tannins complex dietary proteins and metabolic proteins (e.g. bacteria, enzymes, epithelial cells).

          Tannins may reduce intake by decreasing palatability and by negatively affecting digestion.

          • Palatability is reduced because tannins are astringent. Astringency is the sensation caused by the formation of complexes between tannins and salivary glycoproteins.
            • Low palatability depresses feed intake and, thus, animal productivity.
            • Some caution must be taken when interpreting these results. In many trials, commercial tannins sources were used. These types of tannins are usually more effective at lowering feed intakes than naturally-occurring tannins.
            • Another likely problem in many trials is that often only extractable tannins are measured and insoluble tannins are not quantified. However, insoluble tannins may have equal or greater biological activity than those that are more easily extracted.
            • When naturally-occurring tannins are used, these tannins do not always reduce intake. In some trials, tannin-rich diets were eaten in equal or larger amounts than low or free tannin diets.
            • PEG has a higher affinity to tannins than do proteins.
            • PEG can be sprayed on the forages or added in the diet and is fairly inexpensive.
            • PEG utilization can increase feed palatability and digestibility and result in higher animal productivity.

            Usually PAs are not absorbed through the digestive tract. Instead, free tannins and complexed forms remain in the rumen, decreasing protein and plant cell wall digestibility.

            • Several studies have shown that tannins decrease organic matter and fiber digestion.
            • The lower digestibility is the result of the interaction of tannins with cellulase enzymes and rumen bacteria.
            • In some cases, lower fiber digestibility can be the result of a shortage of ruminally fermented nitrogen due to the complexation of proteins by tannins.
            • Field drying and treatments with PEG are able to limit these negative effects.
            • In some cases, lower digestibility was compensated by higher protein outflow from the rumen.
            • In in vivo studies, protein digestibility is greatly reduced when tanniniferous feeds are part of the diet.
            • Plants high in PAs often have proteins linked tightly to the plant cell wall (neutral-detergent insoluble nitrogen, NDIN) and lignin (acid detergent lignin, ADL) components, and, thus, may show negative digestion coefficients when ingested.
              • After ingestion, PAs may also form detergent insoluble tannin-protein complexes with proteins they encounter. These two factors may cause the amount of NDIN and ADL excreted in the feces to exceedthe amount ingested.
              • If protein digestibility is not affected by tannins , proteins behave as a uniform fraction, with a regression coefficient (true digestibility) equal to or larger than 0.88, with a negative intercept(estimate of metabolic endogenous nitrogen, usually about 0.5% of dry matter intake or smaller) and with a low standard error.
              • However, if protein digestibility is affected by tannins , the proteins will behave as a non-uniform fraction, with a regression coefficient (true digestibility) smaller than 0.88, and with a larger negative intercept and a higher standard error
              • If the ratio of soluble to insoluble tannins is high, then protein digestibility is affected more than fiber digestibility.
              • If the same ratio is low, fiber digestibility is the most affected.

              Toxicity to microorganisms

              • Three mechanisms of toxicity have been identified
                • enzyme inhibition and substrate deprivation,
                • action on membranes,
                • metal ion deprivation.
                • secretion of binding polymers,
                • synthesis of tannin-resistant enzymes,
                • biodegradation of tannins (peculiarity of some recently discovered bacteria that are able to tolerate high levels of PA).
                • The major lesions associated with HT poisoning are hemorrhagic gastroenteritis, necrosis of the liver, and kidney damage with proximal tuberal necrosis,
                • High mortality and morbidity were observed in sheep and cattle fed oaks and other tree species with more than 20% HT.
                • PAs are not absorbed by the digestive tract,
                • PAs may damage the mucosa of the gastrointestinal tract, decreasing the absorption of nutrients,
                • PAs may reduce the absorption of essential aminoacids. The most susceptible amino acids are methionine and lysine.
                  • Decreased methionine availability could increase the toxicity of cyanogenic glycosides, because methionine is involved in the detoxification of cyanide via methylation to thiocyanate.

                  Animals fed diets with a level of tannins under 5% experience

                  • depressed growth rates,
                  • low protein utilization,
                  • damage to the mucosal lining of the digestive tract,
                  • alteration in the excretion of certain cations, and
                  • increased excretion of proteins and essential amino acids.

                  In poultry, small quantities of tannins in the diet cause adverse effects

                  • levels from 0.5 to 2.0% can cause depression in growth and egg production,
                  • levels from 3 to 7% can cause death.

                  In swine, similar harmful effects of tannins have been found.

                  The addition of additional proteins or amino acids may alleviate the antinutritional effects of tannins.

                  Levels of tannins above 5% of the diet are often lethal.

                  Animal defense mechanisms

                  Hoatzin: a ruminant-like bird that eats a lot of tannin-rich leaves

                  Some insects consume leaves with high levels of tannins. They are able to adapt to tannins using several available mechanisms

                  • alkaline gut pH,
                  • presence of surfactants to decrease affinity between ingested tannins and protein,
                  • presence of peritrophic membranes that absorb tannins and are then excreted in the feces.

                  Many tannin-consuming animals secrete a tannin-binding protein (mucin) in their saliva.

                  • Tannin-binding capacity of salivary mucin is directly related to its proline content. Advantages in using salivary proline-rich proteins (PRPs) to inactivate tannins are
                    • PRPs inactivate tannins to a greater extent than do dietary proteins this results in reduced fecal nitrogen losses,
                    • PRPs contain non specific nitrogen and nonessential amino acids this makes them more convenient for an animal to exploit rather than using up valuable dietary protein.
                    • Ability to tolerate tannins - deer> goat> sheep> cattle
                    • Consumption of high tannin diets stimulates the development of the salivary glands to permit more PRP production,
                    • Some researchers claim that sheep and cattle do not have any PRPs.

                    Nutritional Effects: positive effects

                    • In sheep and cattle higher retention of nitrogen has been observed in sheep and cattle with low to moderate levels of tannins in forages,
                      • In these cases, the lower apparent and true digestibility of nitrogen was compensated for by reduced urinary loss of hydrogen,

                      Several mechanisms have been suggested to explain how tannins influence protein utilization by ruminants -

                      • High quality dietary proteins would be protected, at least in part, from degradation in the rumen and would then be digested more effectively in the intestine. However,
                        • Even when released, tannins are still biologically active and can react with digestive enzymes or other proteins.
                        • Indeed, in nonruminants, tannins decrease intestinal absorption of amino acids (especially methionine) and reduce growth.
                        • Tannin-protein complexes that are strong enough to survive the environment of the rumen may not be broken down and digested in the lower tract.
                        • Tannins lower the rate of protein degradation and deamination in the rumen resulting in lower rumen ammonia concentration.
                          • This results in lower plasma urea nitrogen (PUN).
                          • increased rumen escape of dietary proteins,
                          • increase in microbial protein flow (up to 28% in sheep).
                          • Increased saliva production, increased rumen turnover rate, and hence, increased microbial outflow,
                          • Increased nitrogen recycling to the rumen,
                          • Decreased proteolysis and slower fermentation of proteins and non-protein nitrogen in the rumen (particularly important in legume silages) this results in a more even nitrogen availability to bacteria.

                          Microbial flow is usually measured using a microbial internal marker (diaminopimelic acid, DAPA). However, tannins may reduce the extraction of microbial cells walls from digesta and make microbial flows measured with DAPA unreliable

                          Chemical Analysis

                          The amount and type of tannins synthesized by plants varies considerably depending on plant species, cultivars, tissues, stage of development, and environmental conditions. Therefore, the study of the nutritional effects of tannins on animals requires quantification of the tannins present in a particular diet. . Due to the complexity of tannins, several methods have been developed for their quantification. None of them, however, is completely satisfactory.

                          The first factor to consider is how the forage or the feed is consumed by the animal - feeds should be analyzed in the form eaten by the animals

                          If the samples are collected fresh and they have to be stored, freeze-drying is the gentlest method of preservation and is recommended instead of freezing , air or oven-drying .

                          • If freeze drying is too expensive or the equipment is not available, freezing without thawing of the sample before extraction is suggested.
                          • If drying is the only means available for preserving the material, drying temperature should be higher than 40° C (to avoid oxidation by the still active enzymes) and lower than 60° C (to avoid heat damage and polymerization).

                          After cutting the sample should be -

                          • Stored in a cold, dark container,
                          • Cut in small pieces and freeze with liquid nitrogen,
                          • Pulverized with a mortar and a pestle, and
                          • Immediately extracted or freeze dried and stored at -4° C.

                          Tannins are extracted with an aqueous organic solvent.

                          • 70% acetone and 30% water is a more effective extractant than alcoholic solvents.
                            • Acetone inhibits tannin-protein interaction. This is a limitation in protein precipitation assays.
                            • This unextractable fraction cannot be ignored because of its nutritional effects.

                            Sample purification and isolation

                            Tannins need to be purified from low molecular weight phenolics and pigments that are present in crude plants extracts.

                            • Purification is essential for the preparation of suitable standards.
                            • Purification of large quantities of tannins can be done by taking advantage of their absorption by Sephadex LH-20.
                              Reference: Hagerman A.E., Klucher K.M., 1986 - Tannin-protein interaction. In:Plant flavanoids in biology and medicine: biochemical, pharmacological, and structure-activity relationships. Ed. Cody V., Middleton E. Jr., Harborne J. - Alan R. Liss, New York, pp 67-76.
                            • An alternative and faster isolation method has been developed by Giner-Chavez, 1996 (see "mixed assays").

                            Tannin assays can be divided into Colorimetric, Gravimetic, Protein precipitation, and Mixed.

                            A. Colorimetric assays

                            • The reaction is based on the reduction of phosphomolybdic acid by phenols in aqueous alkali.
                            • The method determines the total free phenolic groups and is therefore a method to determine total soluble phenolics (either HT and PA).
                              • Problem: It does not differentiate between tannins and many phenolics that are not tannins. Interfering compounds such as ascorbic acid, tyrosine and possibly glucose are also measured.
                              • Specific for PAs or condensed tannins.
                              • Exo-type reaction - vanillin reacts with the meta-substituted A-ring of flavanols to form a chromophore the number of flavanols is proportional to the absorbance of the solution.
                              • Problems:
                                • Low molecular weight flavanols overreact and large polymers underreact,
                                • Catechin is used as standard. This monomer gives the maximum optical density leading to underestimation of large polymers.
                                • Specific for PAs or condensed tannins
                                • Endo-type reaction - the method involves the HCl catalyzed depolimerization of condensed tannins in butanol to yield a red anthocyanidin product that can be detected spectrophotometrically.
                                • Problem: Tannin polymers are cleaved into dimers or trimers instead of monomers and this leads to underestimation.
                                • The degree of polymerization of the PAs can be estimated by combining the butanol-HCl assay with the vanillin assay
                                  • The acid butanol assay measures the total number of flavanoid residues present and the vanillin assay measures the number of molecules.
                                  • Problem: Not all red pigments dissolve, resulting in tannin underestimation.
                                  • Specific to gallotannins ( one type of HT)
                                  • The sample is subjected to hydrolysis to release gallic acid. The reaction between gallic acid and the dye rhodanine produces an intense color that is measured spectrophotometrically.
                                  • Specific for ellagitannins ( another HT)
                                  • The sample is subjected to hydrolysis to release ellagic acid. The reaction between ellagic acid and the sodium nitrite produce a colored solution that is measured spectrophotometrically.

                                  B. Gravimetric assays

                                  • Determines only soluble tannins present in plant extracts insoluble tannins are not measured.
                                  • Based on the ability of trivalent ytterbium to selectively precipitate polyphenols from plant extracts.
                                  • Advantages:
                                    • Standards are not needed,
                                    • The precipitate can be easily dissolved with oxalic acid to yield a solution of polyphenolics and insoluble Yb-oxalate. The solution can be used for further analysis (colorimetric analysis, chromatography, inhibition studies).
                                    • Not all polyphenols are precipitated.
                                    • Low repeatability in plants with low levels of tannins.
                                    • Determines only soluble tannins present in plant extracts insoluble tannins are not measured.
                                    • PVP irreversibly binds tannins.
                                    • This method is not very sensitive and tends to underestimate tannins.
                                    • Includes soluble and insoluble tannins.
                                    • Steps -
                                      • Measurement of the acid-detergent residue of the NDF (NAD) and the neutral-detergent residue of the ADF (AND),
                                      • The difference NAD-AND is used to estimate tannins. This value has been successfully used in the summative equation of Van Soest to estimate the fraction of the feeds that is indigestible due to the action of tannins.

                                      C. Protein precipitation assays

                                      • This method depends on the formation of complexes between tannins and bovine serum albumin embedded in agar.
                                      • Plant extracts are placed in a well in the agar. They diffuse in the agar and precipitate the albumin if tannins are present. In this case a opaque circle forms.
                                        • The diameter of the circle is proportional to the amount of tannins in the extract
                                        • Suitable standards are necessary to estimate the amount of tannins.
                                        • The most commonly used standard is tannic acid and the results are expressed in tannic acid equivalents.
                                        • This method allows determination of large number of samples with limited laboratory facilities.
                                        • Problem: less useful for quantification than the colorimetric procedures.
                                        • Extraction of tannins from plant samples using 70% aqueous acetone (traditional method).
                                        • Isolation of plant condensed tannins using trivalent ytterbium to prepare the standard.
                                        • Analysis of the condensed tannins using the butanol-HCl method (traditional method).
                                        • External standards have the serious limitation that the extinction coefficients for the chromophores produced with them usually are different from those obtained from the plant extracts
                                          • In other words, each gram of external standard (i.e. cyanidin or quebracho) has a different absorption than each gram of tannin from the plant extract. Moreover, the absorption varies with plant species because of the wide variety of tannin types present in nature.
                                          • In this way, even though not all tannins present in the plants extracts are precipitated by Yb, it is possible to isolate and quantify tannins for each plant that can then be used for the standard curve.
                                          • Using quebracho, the tannin content of Desmodium ovalifolium was found to be over 200% !! However, the value was about ten times smaller when an internal standard was used.


                                          These pages were written by Antonello Cannas , a Ph.D. student in Animal Science, Cornell University. I am from Sardinia, Italy. I work as a researcher in the University of Sassari, Sardinia. My research focuses on dairy sheep nutrition. I have been educated to love tannins , especially when diluted with a 14% aqueous solution of alcohol and matched with aged Sardinian sheep cheese and some bread.

                                          A large part of the text, the pictures, and the chemical structures of tannins have been taken from the Ph.D. Thesis of Bertha Iliana Giner-Chavez , whom, by the way, was my lovely officemate and friend. Her Ph. D. thesis has a very nice introduction and literature review on tannins in animal nutrition. It is the clearest review on the subject I have had a chance to read. Moreover, in her thesis she describes the method she developed to analyze tannins. She is from Mexico, a country where tannins in animal nutrition are as common as jalapeños in human nutrition.

                                          Another very good review from which I fished a lot is the one by Jess Reed .

                                          A great and complete source on tannins is the 13th chapter of the "bible" of animal nutrition written by Peter J. Van Soest , whom, by the way, has been my Advisor during my Master and is my co-Chair for the Ph. D.

                                          White Snakeroot (Ageratina altissima)

                                          An innocuous plant, white snakeroot was responsible for the death of Abraham Lincoln’s mother, Nancy Hanks. White snakeroot is a North American herb with flat-topped clusters of small white flowers and contains a toxic alcohol known as trematol. Unlike those who have died from directly ingesting deadly plants, poor Nancy Hanks was poisoned by simply drinking the milk of a cow who had grazed on the plant. Indeed, both the meat and milk from poisoned livestock can pass the toxin to human consumers. Symptoms of "milk poisoning" include loss of appetite, nausea, weakness, abdominal discomfort, reddened tongue, abnormal acidity of the blood, and death. Luckily farmers are now aware of this life-threatening hazard and make efforts remove the plant from animal pastures.

                                          10.2 Biotechnology in Medicine and Agriculture

                                          It is easy to see how biotechnology can be used for medicinal purposes. Knowledge of the genetic makeup of our species, the genetic basis of heritable diseases, and the invention of technology to manipulate and fix mutant genes provides methods to treat diseases. Biotechnology in agriculture can enhance resistance to disease, pests, and environmental stress to improve both crop yield and quality.

                                          Genetic Diagnosis and Gene Therapy

                                          The process of testing for suspected genetic defects before administering treatment is called genetic diagnosis by genetic testing. In some cases in which a genetic disease is present in an individual’s family, family members may be advised to undergo genetic testing. For example, mutations in the BRCA genes may increase the likelihood of developing breast and ovarian cancers in women and some other cancers in women and men. A woman with breast cancer can be screened for these mutations. If one of the high-risk mutations is found, her female relatives may also wish to be screened for that particular mutation, or simply be more vigilant for the occurrence of cancers. Genetic testing is also offered for fetuses (or embryos with in vitro fertilization) to determine the presence or absence of disease-causing genes in families with specific debilitating diseases.

                                          Concepts in Action

                                          See how human DNA is extracted for uses such as genetic testing.

                                          Gene therapy is a genetic engineering technique that may one day be used to cure certain genetic diseases. In its simplest form, it involves the introduction of a non-mutated gene at a random location in the genome to cure a disease by replacing a protein that may be absent in these individuals because of a genetic mutation. The non-mutated gene is usually introduced into diseased cells as part of a vector transmitted by a virus, such as an adenovirus, that can infect the host cell and deliver the foreign DNA into the genome of the targeted cell (Figure 10.8). To date, gene therapies have been primarily experimental procedures in humans. A few of these experimental treatments have been successful, but the methods may be important in the future as the factors limiting its success are resolved.

                                          Production of Vaccines, Antibiotics, and Hormones

                                          Traditional vaccination strategies use weakened or inactive forms of microorganisms or viruses to stimulate the immune system. Modern techniques use specific genes of microorganisms cloned into vectors and mass-produced in bacteria to make large quantities of specific substances to stimulate the immune system. The substance is then used as a vaccine. In some cases, such as the H1N1 flu vaccine, genes cloned from the virus have been used to combat the constantly changing strains of this virus.

                                          Antibiotics kill bacteria and are naturally produced by microorganisms such as fungi penicillin is perhaps the most well-known example. Antibiotics are produced on a large scale by cultivating and manipulating fungal cells. The fungal cells have typically been genetically modified to improve the yields of the antibiotic compound.

                                          Recombinant DNA technology was used to produce large-scale quantities of the human hormone insulin in E. coli as early as 1978. Previously, it was only possible to treat diabetes with pig insulin, which caused allergic reactions in many humans because of differences in the insulin molecule. In addition, human growth hormone (HGH) is used to treat growth disorders in children. The HGH gene was cloned from a cDNA (complementary DNA) library and inserted into E. coli cells by cloning it into a bacterial vector.

                                          Transgenic Animals

                                          Although several recombinant proteins used in medicine are successfully produced in bacteria, some proteins need a eukaryotic animal host for proper processing. For this reason, genes have been cloned and expressed in animals such as sheep, goats, chickens, and mice. Animals that have been modified to express recombinant DNA are called transgenic animals (Figure 10.9).

                                          Several human proteins are expressed in the milk of transgenic sheep and goats. In one commercial example, the FDA has approved a blood anticoagulant protein that is produced in the milk of transgenic goats for use in humans. Mice have been used extensively for expressing and studying the effects of recombinant genes and mutations.

                                          Transgenic Plants

                                          Manipulating the DNA of plants (creating genetically modified organisms, or GMOs) has helped to create desirable traits such as disease resistance, herbicide, and pest resistance, better nutritional value, and better shelf life (Figure 10.10). Plants are the most important source of food for the human population. Farmers developed ways to select for plant varieties with desirable traits long before modern-day biotechnology practices were established.

                                          Transgenic plants have received DNA from other species. Because they contain unique combinations of genes and are not restricted to the laboratory, transgenic plants and other GMOs are closely monitored by government agencies to ensure that they are fit for human consumption and do not endanger other plant and animal life. Because foreign genes can spread to other species in the environment, particularly in the pollen and seeds of plants, extensive testing is required to ensure ecological stability. Staples like corn, potatoes, and tomatoes were the first crop plants to be genetically engineered.

                                          Transformation of Plants Using Agrobacterium tumefaciens

                                          In plants, tumors caused by the bacterium Agrobacterium tumefaciens occur by transfer of DNA from the bacterium to the plant. The artificial introduction of DNA into plant cells is more challenging than in animal cells because of the thick plant cell wall. Researchers used the natural transfer of DNA from Agrobacterium to a plant host to introduce DNA fragments of their choice into plant hosts. In nature, the disease-causing A. tumefaciens have a set of plasmids that contain genes that integrate into the infected plant cell’s genome. Researchers manipulate the plasmids to carry the desired DNA fragment and insert it into the plant genome.

                                          The Organic Insecticide Bacillus thuringiensis

                                          Bacillus thuringiensis (Bt) is a bacterium that produces protein crystals that are toxic to many insect species that feed on plants. Insects that have eaten Bt toxin stop feeding on the plants within a few hours. After the toxin is activated in the intestines of the insects, death occurs within a couple of days. The crystal toxin genes have been cloned from the bacterium and introduced into plants, therefore allowing plants to produce their own crystal Bt toxin that acts against insects. Bt toxin is safe for the environment and non-toxic to mammals (including humans). As a result, it has been approved for use by organic farmers as a natural insecticide. There is some concern, however, that insects may evolve resistance to the Bt toxin in the same way that bacteria evolve resistance to antibiotics.

                                          FlavrSavr Tomato

                                          The first GM crop to be introduced into the market was the FlavrSavr Tomato produced in 1994. Molecular genetic technology was used to slow down the process of softening and rotting caused by fungal infections, which led to increased shelf life of the GM tomatoes. Additional genetic modification improved the flavor of this tomato. The FlavrSavr tomato did not successfully stay in the market because of problems maintaining and shipping the crop.

                                          A bit of history

                                          Bacillus thuringiensis (Bt) is a very common bacterium found in a variety of distinct environments, from soil, to dessert, to tundra. It was first isolated in 1901 by Japanese biologist Ishiwata Shigetane as he studied the causes of a disease afflicting silkworms. Then in 1911, the German scientist Ernst Berliner re-isolated Bt from flour moth caterpillars that had been collected from Thuringia, Germany (hence the species name). Soon Berliner determined that the Bt bacterium was specifically toxic to certain insect larva and not others. However, it wasn’t until 1928 that anyone attempted to harness Bt as a tool for pest control [4].

                                          Figure 1.Bacillus thuringiensis has been used to control pests for almost a century, with its first agricultural application dating back to 1928 and first commercialization a decade later.

                                          In this first instance, the bacteria were used to fend off European corn borer (Ostrinia nubilalis), which historically has been a common and very damaging corn pest. This initiated the development of the first commercial Bt based biopesticide, Sporine, which was introduced in 1938 in France [4]. Since then, Bt-based biopesticides have been a significant pest control strategy, and are actually a common pest control strategy in organic agriculture. By the 1990s, tens of thousands of Bt strains had been isolated, with toxicity to a broad range of insect species [5].

                                          Still, it was a game changer when the first GM corn engineered with genes from Bt became available in 1995. Since then, crops with Bt genes have come to dominate the majority of varieties planted in the U.S., representing 81% of total corn and 84% of total cotton acreage [5].

                                          Lactobacillus Delbrueckii

                                          One of the most common "good" bacterial strains present in yogurt is Lactobacillus delbrueckii. This strain is a lactin acid-producing organism. A 2005 study, published in "Applied and Environmental Microbiology," found that the bulgaricus species present in the L. delbrueckii is an effective immunomodulator that also helps lactose intolerant individuals metabolize lactose. It readily survives through the digestive tract, aiding in both metabolic activity and digestion. It helps the body maintain regularity while helping to expel partially undigested build-up within the intestines.

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                                          Nutrition and health

                                          Food from trees in forests homegardens, and the plants and wildlife supported by forests are often nutritionally essential to the diet of rural people. The medicinal and other properties of tree products also play an important role in keeping people healthy.

                                          Many forest foods are higher in vitamins and other important nutrients than domesticated varieties. While the vitamin C content of an orange is famously high at 57 mg/100 g, the fruit of the baobab tree has 360 mg/100 g and Ziziphus jujube var. spinosa 1000 mg/100 g. Similarly, on a weight-for-weight basis, wild leaf vegetables contain more riboflavin-another vitamin necessary for good health -than eggs, milk, nuts and fish.

                                          It is estimated that some 250 000 children go blind in south-east Asia every year because of lack of vitamin A. Many forest fruits and their leaves are good sources of beta-carotene, which the body converts into vitamin A. Riboflavin deficiency, responsible for several eye and skin disorders, can be corrected by many forest foods, especially leaves. Iron, needed to produce blood haemoglobin, is abundantly available in many forest foods.

                                          One of the most common causes of dietary deficiencies is the decreasing diversity of diets. Medical surveys have shown that Pacific Islanders, for example, began to consume fewer minerals and vitamins as they became more dependent on imported cereals and developed a preference for introduced vegetables there was a significant decline in health as a result.

                                          In rural Bangladesh it was found that, although people living in `'modern' villages had calorific, protein-rich rice and wheat available all year round, a greater number of people suffered from malnutrition than in `traditional' villages where food was not as readily available. Because of the availability of rice and wheat, the modern villagers were eating less of other foods, and the diet of traditional villagers, which contained more roots, tubers, pulses and vegetables, had a higher mineral and vitamin content.

                                          Traditional medicines, such as the eucalyptus oil used as a decongestant, are important in the food economies of many families: they promote good health and hence improve nutrition.

                                          As well as making a direct contribution to health by improving nutrition, tree products provide the only medicines available to many people in developing countries. Some plants contain high concentrations of chemicals used as the base for modern drugs. Many plants are used traditionally for these medicinal qualities, and others undoubtedly depend on effects not yet exploited in Western medicine. These medicines are important nutritionally. By keeping the body healthy, they not only help it to absorb food efficiently but also increase its ability to fight off infections that might otherwise impair digestion and the ability to eat.

                                          Some trees have specific properties that can improve the quality of water supplies. Moringa species, for example, are used by women in Egypt to clarify turbid water. The tree's seeds contain natural coagulants which can clear water to tap water quality in one to two hours, and eliminate up to 99 percent of bacteria. The fruits of other species are lethal to the snails that act as intermediary hosts of bilharzia, and the water fleas that harbour the guinea worm.

                                          Fuelwood and cooking

                                          In 1984, Somalian refugees fed their bean rations to livestock or threw them away because they could not afford the fuelwood to cook them. Their actions highlight the high cost of fuelwood to rural people in developing countries. Fuelwood is needed both to cook and process food-and is essential to nutritional stability and food security.

                                          Fuelwood scarcity, cost and collection time can reduce the number of meals that are cooked in a day. Scarcity can also reduce the length of

                                          time food is cooked-and this, in turn, can reduce the digestibility, and hence the nutritional value of food, particularly for children.

                                          One common solution is to cook large amounts of food together and to reheat them separately later, as they are needed. However, undercooking and reheating food can present serious health risks. This is especially true of meat, because the parasites and bacteria that meat often supports can be destroyed only by intensive cooking.

                                          Fuelwood scarcity reduces the range of foods that can be eaten. Some tubers and legumes, for instance, contain toxic substances which can be removed only by cooking. Fuelwood shortages also restrict the processing of smoked, dried and cooked foods which can extend the availability of food resources into different seasons.

                                          In some regions, fuelwood shortages are causing an increase in the consumption of less nutritious, commercially processed foods.

                                          LEAVES AND STEMS

                                          Wild leaves, either fresh or dried, are one of the most widely consumed forest foods. As the base for soups, stews and relishes they add flavour to otherwise bland staples such as rice or maize, making them more palatable and thus encouraging consumption. One study in Lushoto, Tanzania, found that people who consumed wild leaf relishes favoured the taste of wild leaves over introduced cultivated vegetables.

                                          Leaves from wild and cultivated trees are often boiled fresh in stews. They can also be dried and powdered, or fermented, to preserve them they can later be made into a paste which is used in stews and soups as a meat substitute.

                                          The carotene, vitamin C, calcium and iron content of leaves varies greatly. One study in Swaziland found that the nutrient content of wild leaves compared favourably with that of the leaves of cultivated plants. In Swaziland, the leaves of 48 different species are used and at least half the adults eat meals which include wild leaves more than twice a week.

                                          The stem of the sago palm contains starch, a valuable carbohydrate, commonly used in cooking in Indonesia. It contains 352 calories/ 100 g and provides 85 percent of the energy intake of people in the rural area of Upper Sepik, in Papua New Guinea.

                                          Leaves are widely used in rural society as spicy supplements to stews and soups and often have a high nutritional value.

                                          SEEDS AND NUTS

                                          The nuts of the coconut, oil palm and babassu palm are at the forefront of nutritionally important nuts and seeds, adding substantial calories, oil and protein to the diet.

                                          (Nutritionally, fats and oils are important for several reasons, not least because they facilitate the absorption of vitamins A, D and E.)

                                          Coconuts are of central dietary importa in many cultures, and account for 7 percent the world's fat consumption. In the areas of northeastern Brazil where the babassu palm grows, its kernels provide oil for an average percent of households. In Sierra Leone, oil from the kernel and fruits of the oil palm is consumed by 96 percent of rural households.

                                          Among other important oil nut trees are, the shea butternut, cashew nut, African breadfruit, the mongongo nut and the Park species. The seeds of Parkia form an import part of the diet in most parts of the Sahel. Fermenting Parkia improves the digestibility the protein and increases the vitamin content of the seeds, providing a nutritious protein fat-rich food known as dawadawa. It is an important ingredient in side dishes, soups a stews made to accompany porridges in northern and western Africa.

                                          The baobab tree is heavily used in Africa as a source of fuelwood, food, oil and even dug-out canoes. The fruit pulp can be dried to produce cream of tartar, and the leaves are added to stews and soups as a nutritious spice.

                                          ROOTS AND TUBERS

                                          Roots and tubers provide carbohydrates an( some minerals, and are often important ingredients in traditional medicines. They used as drought and famine foods, not only because they survive low rainfall periods, b because they can be an important source of water. However, they require time to find a dig up, and often involve extensive process such as soaking and prolonged cooking.


                                          Mushrooms, eaten as meat substitutes and i flavouring, are good sources of protein and minerals. In an analysis of the nutritional values of 30 edible mushrooms from Upper Shaba, Zaire, the mean protein content was found to be 22.7 g/100 g dry weight, with a high calcium and iron content.

                                          Mushrooms are nutritious as well as tasty-one study found that 30 species had a high protein value of 22.7 g/100 g as well as high calcium and iron contents.

                                          GUMS AND SAP

                                          Sap, high in sugars and minerals, is tapped beverages. Gum, used as a food supplement good source of energy and both saps and g, have many medicinal uses. Palm wines froc fermented sap are an important cultural beverage in many areas. For example, in southern Cameroon the wine is consumed in most households several times a week. The gum of Sterculia species, a good source of beta-carotene and vitamin C, is added to soups and stews in northern Senegal. Gum arabic (from Acacia senegal) is a traditionally important food for pastoralists, agriculturalists and hunter-gatherers more recently it became an important source of food for gum collectors. Less than 200 g have been estimated as sufficient to feed a person for a day.


                                          Honey is highly valued almost everywhere for its high energy content: 100 g of honey contain more than 280 calories. Tree blossoms provide a year round food supply for bees and, in turn, the fertilizing action of bees during their hunt for nectar can increase the yields of oilseed, pulses and fruit trees.

                                          Honey is an important source of energy almost everywhere. Hives placed in orchards bring additional benefits by increasing fruit yields.


                                          Forests help to maintain the conditions in rivers necessary for fish to live and breed. In coastal areas, mangrove forests are home to important breeding areas for fish and molluscs, which together provide significant animal protein for many rural communities. Average figures for Nigeria, for instance, show that more than three times as much fish as beef is eaten. In Sarawak, Malaysia and the Peruvian Amazon, 50-60 percent of animal protein comes from fish.

                                          Fish often constitute 60 percent of the animal protein consumed by rural people living in coastal areas. Mangrove swamps are still among the most important sources of fish and shellfish.


                                          The protein content of wild meat-often 20-25 percent by weight-is comparable and sometimes higher than that of meat from domestic animals. Wild meat is an important source of animal protein in many parts of the world, though availability depends on conditions in the forest. Although wild meat is also a good source of iron and vitamins A and B, which are commonly lacking in diets, often only small amounts of meat are consumed because of shortages, high prices and legal restrictions on the hunting of animals.

                                          The protein and vitamin content of insects such as caterpillars has been compared to that of vitamin pills. Studies found that 100 g of termites provide 561 calories, and that bee larvae contain 10 times more vitamin D than fish liver oil and twice as much vitamin A as egg yolk.

                                          Snack food

                                          The term 'snack' implies a peripheral source of food, an implication underlined by most studies which focus on meals eaten or food marketed. But the importance of snack foods such as fruits, tubers, animals and insects particularly for children, is increasingly acknowledged. A study in Gambia has shown that during the harvest season between 3 and 10 percent of the calories and protein consumed are taken in the forms of snacks.

                                          Fruit, plucked from the tree and eaten raw, is the most common snack food. A Swaziland study found most fruits are eaten away from the homestead by people out herding, working in the fields or walking to school. The study found that children eat more fruit than adults some of the 50 most frequently eaten species are dubbed 'children's food'.

                                          In Kenya, roots and tubers are eaten when herding livestock, and small animals such as snails and insects are eaten as snacks in many areas of the world.

                                          Watch the video: Υβρίδια ανθρώπων - πιθήκων τα πειράματα των Σοβιετικών (December 2021).