Chemical constituents with antioxidant activity from the branches and leaves of Hultholia mimosoides

Abstract

Four undescribed homoisoflavanoids (1–4), one homoflavonoid (5), ten dibenzoxocin derivatives (6a–10a and 6b–10b), one dibenzoxocin-derived phenolic compound (11), one diterpenoid (13), three aliphatic dicarboxylic acid derivatives (14–16), together with the known diterpenoid 12-O-ethylneocaesalpin B (12) were obtained from the branches and leaves of Hultholia mimosoides. Their structures were elucidated by extensive spectroscopic techniques. Notably, each of the dibenzoxocins 6−10 existed as a pair of interconvertible atropisomers and the conformation for these compounds was clarified by NMR and ECD analyses. Protosappanin F (11) was a previously undescribed dibenzoxocin-derived compound in which one of the benzene rings was hydrogenated to a polyoxygenated cyclohexane ring and an ether linkage was established between C-6 and C-12a. The isolated polyphenols were tested for induction of quinone reductase and compounds 3 and 8 showed potent QR-inducing activity in Hepa-1c1c7 cells.