Inhibitors of Xanthine Oxidase and Scavengers of Superoxide Anions from Cryptolepis sanguinolenta (Lindl.) Schlechter (Periplocaceae)

Cryptolepis sanguinolenta (Lindl.) Schlechter (Periplocaceae) is a medicinal plant used in some African countries against infectious and parasitic diseases. Six of its constituent alkaloids have been isolated from the root bark, identified spectroscopically as cryptoquindolinine (1), quindoline (2), neocryptolepine (3), cryptolepine (4), 11-hydroxycryptolepine (5) and biscryptolepine (6), and their interaction with the xanthine-xanthine oxidase enzyme system has been tested. Compound 5 has been shown to inhibit xanthine oxidase and act as a scavenger of superoxide anions. Alkaloids 1–4 and 6 were devoid of effect in both assays at the highest test concentration of 100 mM. These findings suggest the importance, in the manifestation of both activities, of the hydroxyl group present in 5 but not in the other alkaloids.