vescalagin and procyanidin

Vescalagin (

Topics: Biflavonoids; Catechin; Hydrolyzable Tannins; Molecular Structure; Oxidation-Reduction; Proanthocyanidins; Quercus; Wood

The objective of the present investigation was to examine the oral astringency and protein-binding activity of four structurally well-defined tannins, namely, procyanidin [epicatechin16(4-->8)catechin], pentagalloyl glucose (1,2,3,4,6-penta-O-galloyl-beta-D-glucopyranose), castalagin, and grandinin, representing the three main structural categories of tannins, the proanthocyanidins, the gallotannins, and the ellagitannins. Astringency threshold and dos/response were determined by the half-tongue test using a trained human panel. Protein-binding stoichiometry and relative affinity were determined using radioiodinated bovine serum albumin in precipitation or competitive binding assays. Procyanidin and pentagalloyl glucose were perceived as highly astringent compounds and had relatively steep dose/response curves, but castalagin and grandinin had a lower mass threshold for detection. In vitro, procyanidin was the most effective protein-precipitating agent and grandinin the least. Increasing the temperature increased protein precipitation by the hydrolyzable tannins, especially grandinin. All four polyphenols had higher relative affinities for proline-rich proteins than for bovine serum albumin.

Topics: Adult; Biflavonoids; Biphenyl Compounds; Catechin; Catechols; Chemical Precipitation; Dose-Response Relationship, Drug; Female; Glycosides; Heterocyclic Compounds, 4 or More Rings; Humans; Hydrolyzable Tannins; Iodine Radioisotopes; Male; Proanthocyanidins; Protein Binding; Serum Albumin, Bovine; Taste

Three active principles were isolated from the leaf of Melastoma candidum using the screening of hypotensive effects on spontaneously hypertensive rats (SHR). Intravenous injection of castalagin, procyanidin B-2, or helichrysoside into SHR lowered the mean blood pressure in a dose-dependent manner, with helichrysoside being the most potent compound. Plasma noradrenaline (NA) levels, both basal in SHR and elevated in normal rats through cold-stress stimulation, were attenuated by these compounds in a way which was not influenced by adrenalectomy. Decrease of NA release from sympathetic nerves was assumed to be responsible. Moreover, the hypertensive effect of various vasoconstrictors in anesthetized rats was reduced by helichrysoside. The same results were also observed in castalagin or procyanidin B-2 treated animals. The results indicate that the three principles possess the ability to lower blood pressure through a decrease of sympathetic tone as well as due to direct vasodilatation in SHRs.

Topics: Animals; Antihypertensive Agents; Biflavonoids; Biphenyl Compounds; Catechin; Catechols; Chromones; Drugs, Chinese Herbal; Hydrolyzable Tannins; Molecular Structure; Norepinephrine; Proanthocyanidins; Rats; Rats, Inbred SHR; Rats, Inbred WKY