Anti-inflammatory actions of tannins isolated from the bark of Anacardium occidentale L.

A mixture of tannins (hydrolysable and non-hydrolysable) obtained from the bark of Anacardium occidentale L., on i.p. injection, demonstrated apparent anti-inflammatory activity in carrageenan- and dextran-induced rat paw oedemas, cotton pellet granuloma test and adjuvant-induced polyarthritis in rats. At higher doses orally administered tannins also had activity in carrageenan paw oedema and adjuvant arthritis experiments. The tannins i.p. also inhibited acetic acid-induced "writhing responses" in mice and were found to antagonise the permeability-increasing effects in rats of certain mediators of inflammation and to inhibit the migration of leucocytes to an inflammatory site. While not appearing to act by the release of adrenal hormones, tannins may produce effects in a non-specific manner by their astringent properties on cell membranes thus affecting cell functions. The above results should be considered while studying the anti-inflammatory actions of plant extracts which contain tannins.