Potential of Tannnins: A Review
Archana A. Bele,
Varsha M. Jadhav
Traditional systems of medicine like ayurvedic system have major treatment across globe. Tannins play an important role and has wide applications. Tanninsare water-soluble polyphenols that are present in many plant foods. They have been reported to be responsible for decreases in feed intake, growth rate, feed efficiency, net metabolizable energy and protein digestibility in experimental animals. Therefore, foods rich in tannins are considered to be of low nutritional value. However, recent findings indicate that the major effect of tannins was not due to their inhibition on food consumption or digestion but rather the decreased efficiency in converting the absorbed nutrients to new body substances. The anticarcinogenic and antimutagenic potentials of tannins may be related to their antioxidative property, which is important in protecting cellular oxidative damage, including lipid peroxidaton. The antimicrobial activities of tannins are well documented. The growth of many fungi, yeasts, bacteria and viruses was inhibited by tannins. We have also found that tannic acid and propyl gallate, but not gallic acid, were inhibitory to foodborne bacteria, aquatic bacteria and off-flavor-producing microorganisms. Their antimicrobial properties seemed to be associated with the hydrolysis of ester linkage between gallic acid and polyols hydrolyzed after ripening of many edible fruits. Tannins in these fruits thus serve as a natural defense mechanism against microbial infections. Tannins have also been reported to exert other physiological effects, such as to accelerate blood clotting, reduce blood pressure, decrease the serum lipid level, produce liver necrosis and modulate immunoresponses.
Received: December 08, 2009;
Accepted: March 21, 2010;
Published: June 19, 2010
The term tannin was first applied by Seguin in 1796 to denote substances present
in plant extracts, which were able to combine with protein of animal hides;
prevent their putrefication and convert them into leather. Tannins are astringent,
bitter-tasting plant polyphenols that bind and precipitate proteins. The term
tannin refers to the source of tannins used in tanning animal hides into leather;
however, the term is widely applied to any large polyphenolic compound containing
sufficient hydroxyls and other suitable groups (such as carboxyls) to form strong
complexes with proteins and other macromolecules. Tannins have molecular weights
ranging from 500 to over 3,000 (Handa and Kapoor, 2003).
Examples of gallotannins are the gallic acid esters of glucose in tannic acid
(C76H52O46), found in the leaves and bark of
many plant species Tannins may be employed medicinally in antidiarrheal, hemostatic
and antibacterial (Bele et al., 2009) compounds.
Also, they produce different colors with ferric chloride (either blue, blue
black, or green to greenish black) according to the type of tannin. 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 can complex with: Proteins,
starch, cellulose, minerals.
OCCURANCE OF TANNIN
Tannin occur abundantly in following sources Barks, Seeds, Leaves, Roots and rhizomes:
||Barks of cinnamon, wild cherry, cinchona, willow, acacia mimosa
and otherspecies, oak and hamamelis
||Seeds of cocoa, guarana, kola and areca
||Leaves of hamamelis and green tea
||Roots and rhizomes of kramaria (rhatany) and fern
Physicochemical properties: Tannins dissolve in water to form colloidal
solutions but their solubility varies with their degree of polymerization. They
are soluble in alcohol and acetone. The stability of aqueous solution varies
with the structure and is generally moderate e.g., During the extraction with
boiling water (i.e., in the condition of a decoction) tannin such as geranin
decomposes in 30 min to gallic acid, ellagic acid and corilagin. Like all phenols
tannin reacts with ferric chloride. Hydrolysable tannins are polyestsers of
glucose and upon hydrolysis, they release the sugar and either gallic acid,
hexahydrodiphenic acid or both (Edwin-Jarald, 2007).
Extraction: Tannins are generally extracted with water and acetone mixture (methanol is to be avoided because it causes the methanolysis of galloyl depside). The optimal yield is obtained from the fresh tissues or from the frozen or lyophilized tissues, because in the dried drugs, part of the tannin is irreversibly combined to other polymers. After eliminating the acetone by distillation, the pigments and lipids are removed from the aqueous solution y a solvent extraction (e.g., with dichloro methane). Next an ethyl acetate extraction of the aqueous solution separates the dimeric proanthocyanidins and most gallotannins.
Classification: Tannins are usually divided into hydrolyzable tannins
and condensed tannins (proanthocyanidins). At the center of a hydrolyzable tannin
molecule, there is a polyol carbohydrate (usually D-glucose). The hydroxyl groups
of the carbohydrate are partially or totally esterified with phenolic groups
such as gallic acid (in gallotannins) or ellagic acid (in ellagitannins). Hydrolyzable
tannins are hydrolyzed by weak acids or weak bases to produce carbohydrate and
phenolic acids. Condensed tannins, also known as proanthocyanidins, are polymers
of 2 to 50 (or more) flavonoid units that are joined by carbon-carbon bonds,
which are not susceptible to being cleaved by hydrolysis. While hydrolyzable
tannins and most condensed tannins are water soluble, some very large condensed
tannin is insoluble (Evans, 2005).
||Chemical test: Gold beaterskin test-A small piece of
goldbeater's skin soaked in 2% HCl, rinsed with distilled water and placed
in a solution of tannin for 5 min. The skin piece is washed with distilled
water and kept in a solution of ferrous sulphate. A brown colour is produced
on the skin due to the presence of tannins
||Phenazone test: A mixture of aqueous extract (5 mL)
of a drug and sodium acid phosphate (0.5 g) is heated, cooled and filtered.
A solution of phenazone (2%) is added to the filtrate. bulky coloured precipitate
||Gelatin test: To a solution of tannin (0.5-1%) aqueous
solution of gelatin (1%) and sodium chloride (10%) are added. A white buff-coloured
precipitate is obtained (Harborne, 2007)
DRUGS CONTAINING TANNINS
Liquid orals-Terminalia arjuna (Myroballan)
||Medicinal uses: T. arjuna's traditional use
as a cardiotonic has been confirmed by modern research. Although some results
of these studies (performed since the 1930s) appear conflicting (e.g., increases
and decreases in heart rate or blood pressure), the herb seems to work best
when blood supply to the heart is compromised as in ischemic heart disease
or angina Ayurvedic medicine employs T. arjuna to restore balance
of the 3 humors. T. arjuna also has been used as an aphrodisiac,
diuretic and for earaches. This species has reduced cholesterol levels,
as well. Studies done on T. arjuna combinations find the herb to
be the most potent hypolipidemic agent compared with T. bellirica
and T. chebula. T. arjuna may also play a role as an anti-atherogenic
||Chemical constituents: T. arjuna contains tannins,
flavonoids and sterols. Five oleane derivatives, namely, arjunic acid, arjunolic
acid, arjungenin, arjunetin and arjunglucoside I from stem bark extract
of Terminalia arjuna
||Analysis: Extraction and TLC Desitometric Determination
of Triterpenoid Acids (Arjungenin, Arjunolic Acid) from Terminalia arjuna
Stem Bark Without Interference of Tannin). The stem bark of Terminalia
arjuna Linn. (fam: Combretaceae), commonly known as Arjuna in Indian
systems of medicine, is a reputed drug used for various cardiac disorders.
T. arjuna stem bark is reported to contain different groups of chemical
constituents including phenolics, tannins, saponins and triterpenoid acids.
From our earlier experience with tannin containing herbal drugs, we are
aware that tannins interfere in the extraction of certain compounds and
hence in their quantification. In the present experiment, we report a sample
preparation method to overcome the interference of the tannins by adsorbing
them with carboxy methyl cellulose, which facilitates the efficient extraction
of the triterpenoid acids. Further we established TLC densitometric methods
for the quantification of two of the triterpenoid acids of T. arjuna
stem bark viz., arjungenin and arjunolic acid using HPTLC. The methods were
validated in terms of accuracy, precision and repeatability. The calibration
curve showed linearity in the range of 160-480 ng spot-1 and
160-560 ng spot-1 for arjungenin and arjunolic acid, respectively.
The percentage of arjungenin and arjunolic acid were found to be 0.324 and
0.524% w/w in the stem bark by this modified method of extraction, which
was many times higher than when compared to that using the extraction method
without CMC (0.018 and 0.049%, respectively). The study reiterates the importance
of sample preparation in the quantification of non polar phytochemicals
from herbal raw materials, such that the compounds of interest are extracted
efficiently, overcoming the interference of other compounds like tannins
in the matrix of plant material (Kalola and Rajani,
Marketed formulation-Arjuna rishta: Preparation of Arishtas-Arishtas
are medicinal preparation with alcoholic content and are made by fermentation
methods. The drugs either in the powder form or in the form of a decoction in
a solution of sugar are soaked for a particular period of time during this period
the solution with the drugs undergo fermentation generating alcohol and fascilitating
extraction of active principles from the drugs. The alcohol generated in the
preparation serve as a preservative. Drugs prescribed is prepared by boiling
the coarse drug with water. This is then filtered and transferred to an earthen
pot. sugar is dissolved by boiling. If honey is prescribed should not be boiled.
Drugs to be smeared should be in fine powder form. Mouth of the pot is then
covered with earthen lid and sealed by clay smeared cloth which is to be wound
in 7 consecutive layers. The container should be kept in temperature control
room to maintain constant temperature during fermentation, After the fermentation
process the liquid in the plot is decanted strained and bottled.
Solid dosage form-triphala: Triphala is a combination of
||Emblica officinalis (Amla)
||Terminalia chebula (Hirda)
||Terminalia belerica (Behada)
Triphala is one of the longest-used herbal remedies in the world. Triphala,
meaning three fruits, is made from the fruits of three trees that grow throughout
India and the Middle East, including amalaki fruit (Embelica officinalis),
bibhitaki fruit (Terminalia belerica) and haritaki fruit (Terminalia
chebula). In preparing triphala, these fruits are dried, ground into powder
and then blended together according to the precise directions of Ayrurvedic
||Medicinal uses: Triphala is taken as a general health
tonic and useful for constipation. Triphala is a gentle laxative that can
be used daily and is not habit-forming and has no adverse effects on the
intestinal flora. Improves overall health by increasing the efficiency and
absorption of digestion and reduces gas., triphala is used as a blood builder
and purifier and may increase red blood cell count and hemoglobin levels.
Some healers prescribe it for diabetes, for its balancing effect on blood
sugar levels. It also has anti-cholesterol and anti-mucus properties in
the body. Triphala is believed to strengthen the kidneys and liver and is
prescribed for hepatitis sufferers. Triphala is a source of vitamin C and
is believed to improve the function of the immune system. The herbs in triphala
have anti-inflammatory properties. The remedy is prescribed for gout, a
form of arthritis caused by excess uric acid in the body and other inflammatory
conditions. Triphala is said to have a calming and tonic effect on the nervous
system and is recommended for Alzheimer's disease and other degenerative
disorders of the nervous system.
Another use for triphala is to strengthen the eyes, particularly in cases of
cataracts, glaucoma and conjunctivitis. It can be used as eyewash and may reduce
soreness and redness in the eyes. Triphala can also be applied topically to
the skin to speed the healing of bruises and sunburn.
||Chemical constituents: The major chemical constituents
of Amla are Phyllemblin, Ascorbic acid (vitamin C), Gallic acid, Tannins,
Pectin etc. Myrobalam fruits are the important source of tannin. The tannin
of myrobalam are pyrogallol type (hydrolysable tannin). Chebulagic acid,
chebulinic acid and corilagin are the hydrolysable .Tannin while chebulic
acid, ellagic acid and gallic acid are the other contents. It is also contain
glucose, sorbital, gentiobiose and other Sugar in traces. The dried fruit
T. bellerica contains about 20% tannins of both condensed and hydrolysable
type. Other constituents identified in the fruit include lipids (-sitosterol,
saponins, gallic and ellagic acids and their derivatives, glycosides and
||Analysis: The fruits of T. chebula, T.
bellerica and E. officinalis were powdered separately and 5 g
of powder of each was extracted using 100 mL of 70% aqueous acetone by Soxhlet
extraction. The concentrated extracts were evaporated to dryness under reduced
pressure at 45° and the extractive values were calculated. These extracts
were further used for the estimation of total polyphenols and antioxidant
evaluation. The amounts of total polyphenols in the fruit extracts were
determined according to the Prussian blue method using 1% gum acacia and
85% phosphoric acid as a color stabilizer. To 0.1 mL of sample solutions,
1 mL of 0.016 M K3 Fe(CN)6 was added followed immediately
by 1 mL of 0.02 M FeCl 3 in 0.1 N HCl. The contents were mixed
well and kept at room temperature for 15 min. This was followed by addition
of 5 mL of stabilizer containing water, 85% H3 PO4
and 1% gum acacia in volume proportions of 3:1:1. The contents were vortexed
and the colour density was measured at 700 nm against a reagent blank consisting
of all of the reagents except the polyphenols using Shimadzu UV/Vis spectrophotometer-1601.
The total polyphenol contents were calculated as% w/w of gallic acid equivalents
(Palavy and Priscilla, 2006)
Marketed formulation: Triphala tablet, triphala choorna:
||Formulation of choornam: This is a dry fine powder
form of the drug choornam can be used both internally and externally
||Preparation: The drug selected is washed cleaned and
dried. The fineness of the powder using a pulveriser. The fineness of the
powder improve the therapeutic efficacy. In case of compound choornas each
drug should be powdered separately and finally all individual drug powder
are to be mixed. The choorna should be fine of atleast 80 mesh sieve
Semisolid dosage form: Rosemary leaf
||Medicinal uses: Rosemary is a stimulant of the circulatory
system. Externally, it is used to treat bites, stings, sores, eczema, bruises
and wounds. It is also used in lotions to ease rheumatism and arthritis
Mixed with borax and used cold, it is said to make a nice-smelling hair
wash that can prevent dandruff and stimulate hair growth. Rosemary is particularly
effective at treating oily skin and oily hair, helping to restore proper
balance and oil levels. Rosemary's powerful antimicrobial properties help
to prevent infections and treat skin conditions such as athlete's foot,
psoriasis, eczema, shingles and neuralgia
Internally, it's used to treat migraines, bad breath and to stimulate the sexual
organs (but it can be an irritant to the stomach, intestines and kidneys, so
use it sparingly). Rosemary is also used to treat nervous disorders, upset stomachs
and to regulate the menstrual cycle and ease cramps. Mix the crushed leaves
generously into meats, fish, potato salads, etc. at your next picnic to prevent
food poisoning. The essential oil is used in aromatherapyas an inhalant and
decongestant and to enhance memory and clear concentration. Rosemary is taken
by mouth to treat indigestion, headache, stress, nervous tension, as well as
to promote menstrual flow and to raise low blood pressure. It's put on the skin
to stop redness and pain and to treat fibromyalgia and sciatica (pain in the
muscles and nerves). Rosemary oil has been used to promote wound healing.
||Chemical constituents: Rosemary leaf contains phenolic
acids (2-3% rosmarinic, chlorogenic, caffeic acids); phenolic diterpenoid
bitter substances (up to 4.6% carnosol, rosmaridiphenol, rosmanol); triterpenoid
acids (oleanolic acid, ursolic acid); flavonoids (apigenin, luteolin, nepetin,
nepitrin); 1.2-2.5% volatile oil, of which 15-50% is 1,8-cineole, 15-25%
a-pinene, 12-24% a-terpineol, 10-25% camphor, 5-10% camphene, 1-6% borneol,
1-5% bornyl acetate and tannins
||Analysis: Rosmarinus officinalis extracts were
investigated by a combination of bioassays and biochemical analysis to identify
bioactive compounds. The 2,2-diphenyl-2-picrylhydracyl hydrate (DPPH) radical
scavenging method, Folin-Ciocaulteau method and HPLC chromatography were
used to study the distribution and levels of antioxidants (AOXs). Antimicrobial
activity analysis was carried out using the disk diffusion and broth dilution
techniques. A good correlation between the AOX activities and total phenol
content in the extracts was found. Although all rosemary extracts showed
a high radical scavenging activity, a different efficacy as antimicrobial
agent was observed. Methanol extract containing 30% of carnosic acid, 16%
of carnosol and 5% of rosmarinic acid was the most effective antimicrobial
against Gram-positive bacteria (minimal inhibition concentration, MIC, between
2 and 15 μg mL-1), Gram negative bacteria (MIC between 2
and 60 μg mL-1) and yeast (MIC of 4 μg mL-1).
By contrast, water extract containing only 15% of rosmarinic acid showed
a narrow activity. MIC value of the methanol and water extracts is in a
good correlation with the values obtained with pure carnosic acid and rosmarinic
acid, respectively. Therefore, our results suggested that the antimicrobial
rosemary extracts efficacy was associated with their specific phenolic composition.
Carnosic acid and rosmarinic acid may be the main bioactive antimicrobial
compounds present in rosemary extracts. From a practical point of view,
rosemary extract may be a good candidate for functional foods as well as
for pharmaceutical plant-based products (Moreno et
Marketed formulation-Lubrajel: Neutraceuticals-(I) Pomegranate:
Punica Granatum (Pomegranate)
||Medicinal uses: A decotion of seed is used to treat
syphilis. Juice used to treat jaundice and diarrhoea. Juice of flower is
used to treat nose bleeds. The fruit pulp and the seed are stomachic. Pomegranate
juice enters into preparations for treating dyspepsia and is considered
beneficial in leprosy. Because of their tannin content, extracts of the
bark, leaves, immature fruit and fruit rind have been given as astringents
to halt diarrhea, dysentery and hemorrhages
||Chemical constituents: One pomegranate delivers 40%
of an adult's daily vitamin C requirement. It is also a rich source of folic
acid and of antioxidants Pomegranates are high in polyphenols. The most
abundant polyphenols in pomegranate are hydrolysable tannins, particularly
punicalagins, which have been shown in many peer-reviewed research publications
to be the antioxidant responsible for the free-radical scavenging ability
of pomegranate juice
||Analysis: Quantitative determination of the polyphenolic
content of pomegranate peel
The quantitative determination of total phenols, ellagic tannins and gallic
and ellagic acids in the peel of the Tunisian pomegranate variety Chelfi, has
been carried out. The ellagic tannin content is prominently less than the amount
of total phenols, which led us to look for the presence of the condensed tannins.
The determination of the content of catechic tannins in eight Tunisian varieties
of the pomegranate was carried out using weekly samples over a period of 2 months.
Analysis of ellagic tannins. The absorbance was measured to its maximum at
590 nm by means of a spectrometer UV-Visible Shimadzu (UV. 260) (Ben-Nasr
et al., 1996).
Marketed formulation: (i) Pomeratrol capsules 60-20 mg. (ii) t'Zerah
- Pomegranate beauty and skin.
Cosmetics: Hair dye: This product contains a natural tannin (from Neutral Henna a plant ingredient) known as hennotannic acid. Tannins are slightly astringent and their use will tighten the surface of the scalp and hair follicles, strengthening the follicles' grasp on each hair. Hennotannic acid coats the hair. It seals in oils and tightens the hair cuticle giving your hair a rich, healthy gentle shine.
||Chemical constituents: The constituents of Henna is
found in it in a brown substance of a resinoid fracture, having the chemical
properties which characterize the tannins and therefore named hennotannic
acid. Dried, powdered leaves of henna contain about 0.5 to 1.5% lawsone,
the chief constituent responsible for the dyeing properties of the plant.
Henna also contains mannite, tannic acid, 2-hydroxy-1:4-naphthoquinone resin
mucilage, gallic acid, glucose, mannitol, fat, resin and mucilage are also
present. The colouring matter is the quinone and napthaquinone. Lawsone,
the dye molecule in henna will bind with protein, such as the keratin in
fingernails, hair and skin
||Analysis: A fixed wavelength of 248 nm; lawsone Rt
= 6.3 min. The identification of lawsone was confirmed by UV. spectrum,
Rt and by spike analysis using pure standard
||Marketed formulation: Herbal Heena- Herbal Henna is
available in pure form and without any additives. It is obtained by mixing
13 different herbs. The product helps in removing dandruff and prevents
hair loss. Herbal henna is popular in the international market because it
increases the longevity of hair, is a natural conditioner and removes dryness.
It is perfectly safe and has no ill effects
Tannins are astringent, bitter-tasting plant polyphenols that bind and precipitate proteins,applied to any large polyphenolic compound containing sufficient hydroxyls and other suitable groups (such as carboxyls) to form strong complexes with proteins and other macromolecules. Tannins have molecular weights ranging from 500 to over 3,000. Tannins have the property of binding proteins together, even precipitate them, so they affect the proteins in saliva making them stringy, hence the effect on the inside of the mouth. They also have the ability to react with bacterial cell walls, polysaccharides, carbohydrates and enzymes, all present in the mouth In the plant, tannins are defensive compounds that counteract bacteria and fungi by interfering with their surface proteins The sensation of astringency is caused by the tanning of the proteins in the saliva and mucous membranes of the mouth; lubrication is reduced and the surface tissues actually contract. Pharmaceutical, chemical, microbiological and analytical part also serves an important part to study drugs containing tannins. Therapeutic applications of tannin containing drugs also play an important role. 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), in tea, in chocolate, in legume forages (trefoil), in legume trees (Acacia sp., Sesbania sp.), in grasses (sorghum, corn)
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5: Palavy, K. and M.D. Priscilla, 2006. Standardisation of selected Indian Medicinal Herbal raw material containing polyphenols as major constituents. J. Pharmaceutical Sciences, 68: 506-509.
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6: Nasr, C.B., N. Ayed and M. Metche, 1996. Quantitative determination of the polyphenolic content of pomegranate peel. Zeitschrzfi fur Lebensmittel Unterschung Forschung, 203: 374-378.
7: Bele, A.A., J.M. Varsha, S.R. Nikam and J.K. Vilasrao, 2009. Antibacterial potential of herbal formulation. Res. J. Microbiol., 4: 164-167.
8: Moreno, T., C.S. Scheyer and A.A. Vojnov, 2006. Antioxidant and antimicrobial of rosemary extracts linked to their polyphenol composition. Free Radical Res., 40: 223-231.
9: Kalola, J. and M. Rajani, 2006. Extraction and TLC desitometric determination of triterpenoid acids (Arjungenin, Arjunolic Acid) from Terminalia arjuna stem bark without interference of tannins. Chromatographia, 63: 475-481.
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