Proanthocyanidins (syn condensed tannins) are complex flavonoid polymers naturally present in cereals, legume seeds and particularly abundant in some fruits and fruit juices. They share some common structural features—phenolic nature and high molecular weight—with phenolic polymers found in black tea and red wine (called here tannin-like compounds). The polymeric nature of proanthocyanidins makes their analysis and estimation in food difficult. For this reason, little is known about their consumption, although they likely contribute a large part of the daily polyphenol intake. They also share common physicochemical properties: they form stable complexes with metal ions and with proteins and are, like other polyphenols, good reducing agents. Many of their biological effects of nutritional interest derive from these properties. As metal ion chelators, they influence the bioavailability of several minerals. The nutritional significance of the non-specific complexation of proteins is less clear. As reducing agents, they may participate in the prevention of cancers, both of the digestive tract and inner organs. They may also protect LDLs against oxidation and inhibit platelet aggregation and therefore prevent cardiovascular diseases. In vitro, animal and human studies on the prevention of these chronic diseases are reviewed with particular attention to wine and tea polyphenols. The lack of data on their bioavailability and the paucity of human studies are emphasised.

© 2000 Society of Chemical Industry

Proanthocyanidins and tannin-like compounds – nature, occurrence, dietary intake and effects on nutrition and health

The biological properties of dietary polyphenols are greatly dependent on their bioavailability that, in turn, is largely influenced by their degree of polymerization. The gut microbiota play a key role in modulating the production, bioavailability and, thus, the biological activities of phenolic metabolites, particularly after the intake of food containing high-molecular-weight polyphenols. In addition, evidence is emerging on the activity of dietary polyphenols on the modulation of the colonic microbial population composition or activity. However, although the great range of health-promoting activities of dietary polyphenols has been widely investigated, their effect on the modulation of the gut ecology and the two-way relationship "polyphenols ↔ microbiota" are still poorly understood. Only a few studies have examined the impact of dietary polyphenols on the human gut microbiota, and most were focused on single polyphenol molecules and selected bacterial populations. This review focuses on the reciprocal interactions between the gut microbiota and polyphenols, the mechanisms of action and the consequences of these interactions on human health.

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Benefits of polyphenols on gut microbiota and implications in human health.

Review on some plants of Indian traditional medicine with antioxidant activity.

http://siba.unipv.it/farmacia/art/Marrubini/Nat%20Prod%20Rep%202001.pdf

Tannins: Classification and Definition

Tannins are a unique group of phenolic metabolites with molecular weights between 500 and 30 000 Da, which are widely distributed in almost all plant foods and beverages. Proanthocyanidins and hydrolysable tannins are the two major groups of these bioactive compounds, but complex tannins containing structural elements of both groups and specific tannins in marine brown algae have also been described. Most literature data on food tannins refer only to oligomeric compounds that are extracted with aqueous-organic solvents, but a significant number of non-extractable tannins are usually not mentioned in the literature. The biological effects of tannins usually depend on their grade of polymerisation and solubility. Highly polymerised tannins exhibit low bioaccessibility in the small intestine and low fermentability by colonic microflora. This review summarises a new approach to analysis of extractable and non-extractable tannins, major food sources, and effects of storage and processing on tannin content and bioavailability. Biological properties such as antioxidant, antimicrobial and antiviral effects are also described. In addition, the role of tannins in diabetes mellitus has been discussed.

Tannins: current knowledge of food sources, intake, bioavailability and biological effects.

To identify substances with anti-human immunodeficiency virus (HIV) activity in traditional medicines, water and methanol extracts of crude drugs used in Indian traditional medicine (Ayurveda) were subjected to screening for their inhibitory effects on HIV type 1 protease (PR) The enzyme activity was determined by HPLC and of the 39 crude drugs tested, the extracts of the seeds of Areca catechu, the bark of Eugenia jambolana, the bark of Saraca indica and the stem bark of Terminalia arjuna inhibited the HIV-1 PR activity by more than 70% at a concentration of 02 mg/mL The most potent inhibition was shown by the A catechu extract, from which some procyanidins were isolated One of them, arecatannin B1 showed significant HIV-1-PR inhibitory activity

Screening of various plant extracts used in ayurvedic medicine for inhibitory effects on human immunodeficiency virus type 1 (HIV-1) protease

Extracts of 41 medicinal plants used in Egyptian folk medicine were screened for their inhibitory effects on human immunodeficiency virus-1 reverse transcriptase. The extracts of fruits of Phyllanthus emblica, Quercus pedunculata, Rumex cyprius, Terminalia bellerica, Terminalia chebula and Terminalia horrida showed significant inhibitory activity with IC50 < or = 50 micrograms/ml. Through a bioassay guided-fractionation of the methanol extract of the fruit of P. emblica, putranjivain A (1) was isolated as a potent inhibitory substance with IC50 = 3.9 microM, together with 1,6-di-O-galloyl-beta-D-glucose (2), 1-O-galloyl-beta-D-glucose (3), kaempferol-3-O-beta-D-glucoside (4), quercetin-3-O-beta-D-glucoside (5) and digallic acid (6). The inhibitory mode of action by 1, 2 and 6 was non-competitive with respect to the substrate but competitive with respect to a template-primer. Furthermore, the stereochemistry of 1 was established in this paper by nuclear magnetic resonance spectroscopy.

Inhibitory effects of Egyptian folk medicines on human immunodeficiency virus (HIV) reverse transcriptase

In the course of our studies on the development of anti-plaque agents for prevention of dental caries, we investigated effects of some of tea preparations and their individual components on the glucan synthesis catalyzed by glucosyltransferase (GTF) from Streptococcus mutans. Extracts of green tea and black tea, and polyphenol mixtures showed appreciable inhibition in the synthesis of insoluble glucan. Among the components isolated from tea infusions, theaflavin and its mono- and digallates had potent inhibitory activities at concentrations of 1-10 mM against GTF. (+)-Catechin, (-)-epicatechin and their enantiomers had moderate inhibitory activities at these concentrations, while galloyl esters of (-)-epicatechin, (-)-epigallocatechin and (-)-gallocatechin had increased inhibitory activities.

Effect of tea polyphenols on glucan synthesis by glucosyltransferase from Streptococcus mutans

Of 30 Indonesian plant extracts tested for their human immunodeficiency virus type-1 (HIV-1) inhibitory activities, six were shown to be effective by assays using HIV-1-infected MT-4 cells: a methanol extract of mahoni (bark of Swietenia mahagoni) and water extracts of benalu teh (stems and branches of Loranthus parasiticus), kiules (fruit of Helicteres isora), supratul (fruits of Sindora sumatrana), sambiloto (leaves of Andrographis paniculata) and temu ireng (rhizoma of Curcuma aeruginosa). Their ED50 values ranged from 4.2 to 175 μg/mL. The samples also suppressed the formation of syncytia in co-cultures of MOLT-4 and MOLT-4/HIV-1 cells. The most potent inhibitor was a methanol extract of mahoni, which also showed a significant inhibition of HIV-1 protease.

Screening of Indonesian plant extracts for anti‐human immunodeficiency virus—type 1 (HIV‐1) activity

Methanol and water extracts of 30 Indonesian medicinal plants were tested for inhibitory activity on avian myeloblastosis virus (AMV)-reverse transcriptase (RT). The most potent inhibition was shown by extracts of Loranthus parasiticus (whole plant), Helicteres isora (fruit), Terminalia belerica (fruit peel), Strobilanthes crispus (leaves) and Woodfordia floribunda (flower and leaves). Two kinds of template-primers, (rA) n -(dT) 12−18 , and (rC) n -(dG) 12−18 , were examined for polymerization reaction but the inhibitory activity was stronger in the (rC) n -(dG) 12−18 , directed reaction in most of the samples. These extracts showed no appreciable cytotoxicity at concentrations where over 90% of RT activity was inhibited

Ines Tomoco Kusumoto

Papers

Screening of various plant extracts used in ayurvedic medicine for inhibitory effects on human immunodeficiency virus type 1 (HIV-1) protease

Inhibitory effects of Egyptian folk medicines on human immunodeficiency virus (HIV) reverse transcriptase

Effect of tea polyphenols on glucan synthesis by glucosyltransferase from Streptococcus mutans

Screening of Indonesian plant extracts for anti‐human immunodeficiency virus—type 1 (HIV‐1) activity

Inhibitory effects of indonesian plant extracts on reverse transcriptase of an RNA Tumour Virus (I)