Structure-antioxidant activity relationships of flavonoids isolated from different plant species

In the course of our phytochem. studies of different plants from developing countries, several flavonoid derivs. were isolated and structurally characterized, both aglycons and glycosides, typical of the species investigated. The aim of this study was to evaluate varieties of medicinal plants that were growing in developing countries, known in traditional medicine as anti-inflammatory remedies, with respect to their flavonoidic isolated constituents, assuming that their anti-inflammatory activity could be explained, at least in part, by the presence of antioxidant principles. The antioxidant activities of compds. were evaluated by measuring their ability to scavenge the radical cation 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonate) (ABTS+) and the superoxide anion, to inhibit -carotene oxidn. in a lipid micelle system, and to inhibit xanthine oxidase activity, showing some structure-activity relationships.