Hydrolysable tannin

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A hydrolysable tannin or pyrogallol-type tannin is a type of tannin that, on heating with hydrochloric or sulfuric acids, yields gallic or ellagic acids. [1]

Contents

At the center of a hydrolysable tannin molecule, there is a carbohydrate (usually D-glucose but also cyclitols like quinic or shikimic acids). 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. Hydrolysable tannins are mixtures of polygalloyl glucoses and/or poly-galloyl quinic acid derivatives containing in between 3 up to 12 gallic acid residues per molecule. [2]

Hydrolysable tannins are hydrolysed by weak acids or weak bases to produce carbohydrate and phenolic acids.

Examples of gallotannins are the gallic acid esters of glucose in tannic acid (C76H52O46), found in the leaves and bark of many plant species.

Hydrolysable tannins can be extracted from different vegetable plants, such as chestnut wood ( Castanea sativa ), oak wood ( Quercus robur , Quercus petraea and Quercus alba ), tara pods ( Caesalpinia spinosa ), gallnuts ( Quercus infectoria and Rhus semialata ), myrobalan ( Terminalia chebula ), sumac ( Rhus coriaria ) and Aleppo gallnuts ( Andricus kollari ). [3] [4]

Analysis

Gallic acid determination

50 mg of sample tannin in 5 ml 2N H2SO4 are put into constricted test tubes and frozen. The tubes are vacuum-sealed and heated for 24 hours at 100 °C. The tubes are cooled, opened and the contents made up to 50 ml with water. Then 1.5 ml of freshly prepared 0.667% w/v rhodanine in methanol and 1 ml of sample are mixed. After exactly 5 min 1 ml of 0.5 N KOH solution is added. After 2.5 min the mixture is diluted to 25 ml with distilled water and 5–10 min later the absorbance at 520 nm is measured. The measured absorbance obeys the relationship:
A520= [0.13 × (mg of gallic acid) ] +0.03
Gallic acid is used as a standard and the data are based on experiments carried out in triplicate.

Ellagic acid determination

10 mg of samples tannin in 1 ml 2N H2SO4 are put into constricted test tubes and frozen. The tubes are vacuum-waled and heated for 24 hours at 100 °C. Tubes were cooled, opened and the filtered content made up to 10 ml with pyridine. Then 1.1 ml of pyridine and l ml of sample are mixed in a dry test tube. After adding 0.10 ml of concentrated HCl and mixing, the sample is brought to 30 °C. The sample is quickly mixed after 0.10 ml of 1% (w/v) NaNO2 in water and the absorbance 538 nm is immediately recorded. After a 36 min incubating period at 30 °C, the absorbance is again recorded. The difference between the initial absorbance and the absorbance at 36 min (D A538) is proportional to the ellagic acid concentration. The measured absorbance obeys the relationship:
A538 = [0.03 × (mg of ellagic acid)] – 0.04
Ellagic acid is used as a standard and the data were based on experiments carried out in triplicate.

Alkaline hydrolysis

4.8 g sample tannin in 9 ml water are refluxed in 4.2 ml 40% NaOH for 6h at pH 12 - 13. Neutralization to pH = 6.8 - 7 is performed with 62% H2SO4.

HPLC determination

Uses

Tannins, including gallo and ellagic acid (epigallitannins), are inhibitors of HIV replication. 1,3,4-Tri-O-galloylquinic acid, 3,5-di-O-galloyl-shikimic acid, 3,4,5-tri-O-galloylshikimic acid, punicalin, punicalagin inhibited HIV replication in infected H9 lymphocytes with little cytotoxicity. Two compounds, punicalin and punicacortein C, inhibited purified HIV reverse transcriptase. [5]

Hydrolysable tannins have shown also potential antibacterial effects against Helicobacter pylori . [6]

In the past few years, hydrolysable tannins have also been studied for their potential effects against cancer through different mechanisms. [7] [8]

Related Research Articles

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<span class="mw-page-title-main">Polyphenol</span> Class of chemical compounds

Polyphenols are a large family of naturally occurring organic compounds characterized by multiples of phenol units. They are abundant in plants and structurally diverse. Polyphenols include flavonoids, tannic acid, and ellagitannin, some of which have been used historically as dyes and for tanning garments.

<span class="mw-page-title-main">Tannic acid</span> Chemical compound

Tannic acid is a specific form of tannin, a type of polyphenol. Its weak acidity (pKa around 6) is due to the numerous phenol groups in the structure. The chemical formula for commercial tannic acid is often given as C76H52O46, which corresponds with decagalloyl glucose, but in fact it is a mixture of polygalloyl glucoses or polygalloyl quinic acid esters with the number of galloyl moieties per molecule ranging from 2 up to 12 depending on the plant source used to extract the tannic acid. Commercial tannic acid is usually extracted from any of the following plant parts: Tara pods (Caesalpinia spinosa), gallnuts from Rhus semialata or Quercus infectoria or Sicilian sumac leaves (Rhus coriaria).

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The enzyme tannase (EC 3.1.1.20) catalyzes the following reaction:

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<i>Quercus infectoria</i> Species of oak tree

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<span class="mw-page-title-main">Hexahydroxydiphenic acid</span> Oxidatively coupled derivative of gallic acid

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<span class="mw-page-title-main">Valoneic acid</span> Chemical compound

Valoneic acid is a hydrolysable tannin. It is a component of some hydrolysable tannins such as mallojaponin.

<span class="mw-page-title-main">Pomegranate ellagitannin</span> Ellagitannins found in the pomegranate fruit

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Maximilian Nierenstein was a professor of biochemistry at the University of Bristol.

<span class="mw-page-title-main">Sanguisorbic acid</span> Chemical compound

Sanguisorbic acid is a constituent of some ellagitannins. It is constituted by a hexahydroxydiphenic acid unit linked by an O-C bond to a gallic acid. The differences with its isomers, valoneic acid and nonahydroxytriphenic acid, are that the hydroxyl that links the hexahydroxydiphenoyl (HHDP) group to the galloyl group belongs to the galloyl group in valoneic acid, while in nonahydroxytriphenic acid, the hexahydroxydiphenic acid unit is linked by a C-C bond to gallic acid.

<i>Terminalia macroptera</i> Species of flowering plant

Terminalia macroptera is a species of flowering plant in the Combretaceae known by the Hausa common name kwandari. It is native to Africa, where it can be found in Benin, Burkina Faso, Ghana, Senegal, Sudan, Uganda, and Nigeria.

<span class="mw-page-title-main">Tellimagrandin I</span> Chemical compound

Tellimagrandin I is an ellagitannin found in plants, such as Cornus canadensis, Eucalyptus globulus, Melaleuca styphelioides, Rosa rugosa, and walnut. It is composed of two galloyl and one hexahydroxydiphenyl groups bound to a glucose residue. It differs from Tellimagrandin II only by a hydroxyl group instead of a third galloyl group. It is also structurally similar to punigluconin and pedunculagin, two more ellagitannin monomers.

References

  1. ↑ "Notes on Tannins from PharmaXChange.info". Archived from the original on 2015-01-04. Retrieved 2010-09-13.
  2. ↑ Pentagalloyl glucose on www.natural-specialities.com Archived 2010-10-12 at the Wayback Machine
  3. ↑ Haslam E. Plant Polyphenols, Vegetable Tannins Revisited. Cambridge University Press, Cambridge, UK (1989).
  4. ↑ Hemingway RW, Laks PE. Plant polyphenols Plant Polyphenols: Synthesis, Properties and Significance. Springer (1992).
  5. ↑ Nonaka G, Nishioka I, Nishizawa M, et al. (1990). "Anti-AIDS agents, 2: Inhibitory effects of tannins on HIV reverse transcriptase and HIV replication in H9 lymphocyte cells". J. Nat. Prod. 53 (3): 587–95. doi:10.1021/np50069a008. PMID   1698933.
  6. ↑ Funatogawa K, Hayashi S, Shimomura H, et al. (2004). "Antibacterial activity of hydrolyzable tannins derived from medicinal plants against Helicobacter pylori". Microbiol. Immunol. 48 (4): 251–61. doi: 10.1111/j.1348-0421.2004.tb03521.x . PMID   15107535.
  7. ↑ Yang LL, Lee CY, Yen KY (August 2000). "Induction of apoptosis by hydrolyzable tannins from Eugenia jambos L. on human leukemia cells". Cancer Lett. 157 (1): 65–75. doi:10.1016/S0304-3835(00)00477-8. PMID   10893444.
  8. ↑ Tanimura S, Kadomoto R, Tanaka T, Zhang YJ, Kouno I, Kohno M (May 2005). "Suppression of tumor cell invasiveness by hydrolyzable tannins (plant polyphenols) via the inhibition of matrix metalloproteinase-2/-9 activity". Biochem. Biophys. Res. Commun. 330 (4): 1306–13. doi:10.1016/j.bbrc.2005.03.116. PMID   15823585.
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