Constituents of Cuscuto Reflexa are anti-HIV Agents

Abstract

Crude water extracts of Cuscuta reflexa exhibited anti-HIV activity. Fractionation of the crude extract led to the isolation of nine pure compounds with closely related structures, showing interesting structure activity relationships. 3,5,7,4′-Tetrahydroxyflavanone (aromadendrin) inhibited infection by binding to V3 loop of gp 120 and inhibiting its interaction with CD4, whereas 3,5,7,3′,4′-pentahydroxyflavanone (taxifolin), with an extra OH group in the 3′ position in ring B was less specific and exhibited less selectivity in cell cultures. In general, flavanones containing an extra OH group in the 3′ position (taxifolin, taxifolin-7-O-β-D-glucopyranoside and coccinoside B) were less specific and inhibited viral protease, reverse transcriptase, CD4 /gp120 interaction in vitro and bound to non specific proteins. Other compounds isolated from C reflexa were derivatives of quinic acids; 3,4-O-dicaffeoylquinic acid was more active than 3-O-caffeoyl quinic acid. The anti-HIV activity of crude extract may be the result of combinatory effects with compounds of different modes of action.