Steroids with anti-inflammatory activity from Vernonia nigritiana Oliv. & Hiern

Abstract

The leaves of Vernonia nigritiana Oliv. & Hiern. (Asteraceae) were investigated for their in vivo topical anti-inflammatory properties, following a bioassay-oriented fractionation approach. Petroleum ether, chloroform and chloroform-methanol extracts inhibited the Croton oil-induced ear dermatitis in mice. The chloroform extract was only about half as active as the non steroidal anti-inflammatory drug indomethacin (ID50=237 and 93 μg/cm(2), respectively). Phytochemical investigation of this extract led to the isolation of nine polyhydroxylated stigmasterol glycosides and six polyhydroxylated stigmasterols. Their structures were elucidated by NMR, MS and chemical methods. Each compound exerted a significant anti-oedema activity, the most active being 1 (3β-O-β-D-glucopyranosyloxy-5α-stigmasta-7,9(11),24(28)Z-triene-6β,16β,26,29-tetrol) and 3 (3β-O-β-D-glucopyranosyloxy-5α-stigmasta-7,9(11),24(28)Z-triene-6β,16β,29-triol), only two and five fold less potent than the steroidal drug hydrocortisone (ID50=0.10, 0.21 and 0.04 μmol/cm(2), respectively). Compound 1 (50 μM) also completely inhibited the transcription factor NF-κB in vitro.

Keywords: Anti-inflammatory activity; Asteraceae; Croton oil ear test; NF-κB; Steroids; Vernonia nigritiana.