Constituents of Cuscuta reflexa are anti-HIV agents

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 gp120 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-beta-D-glucopyranoside and coccinoside Bf 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 he the result of combinator), effects with compounds of different modes of action.