Antioxidant naphthoquinones of Sinningia reitzii from Santa Catarina state, Brazil

Abstract

Sinningia reitzii (Hoehne) L. E. Skog (Gesneriaceae) is a subshrub native to Brazil, where it is distributed in two disjunctive populations around the 26°S and 23°S parallels. In this work, tubers of plants from the wild population growing at the 26°S parallel (Santa Catarina state) yielded two new naphthoquinones, 5,6-dihydroxy-7-methoxy-α-dunnione and 8-hydroxy-6,7-dimethoxya- dunnione. Three known compounds were also isolated: 6,8-dihydroxy-7-methoxy-α-dunnione, 5-hydroxy-6,7-dimethoxy-adunnione, and 6,8-dihydroxy-7-methoxy-2-O-methyldunniol. The naphthoquinones 6,8-dihydroxy-7-methoxy-2-O-methyldunniol, 6,8-dihydroxy-7-methoxy-α-dunnione, and 5,6-dihydroxy-7-methoxy-α-dunnione displayed antioxidant activity in the ORAC-FL method, with values of relative trolox equivalent in the range of 1.39-4.83 μmol g-1