Xanthine oxidase inhibitory activity of Lychnophora species from Brazil ("Arnica").

Twenty-two extracts from five Lychnophora species and one Lychnophoriopsis species, traditionally used in Brazil as analgesic, anti-inflammatory, and to treat bruise and rheumatism were examined for the inhibition of xanthine oxidase (XO), the enzyme that catalyses the metabolism of hypoxanthine and xanthine into uric acid. Sixteen extracts were tested. All of them were found to have excellent XO inhibitory activity, with inhibitions greater than 38% at 100 microg/mL in the assay mixture. The most active plants examined were Lychnophora trichocarpha, Lychnophora ericoides, Lychnophora staavioides and Lychnophoriopsis candelabrum, with inhibitions of 77%, 78%, 66% and 63% at 100 microg/mL, respectively, and IC(50) values of 6.16, 8.28, 33.97 and 37.70 microg/mL, respectively.