The aim of this study was to screen active constituents that reverse multidrug resistance( MDR) in P-glycoprotein( Pgp) overexpressing cancer cells from plant Metaplexis hemsleyana Oliv.( Asclepiadaceae). The aerial parts of M.hemsleyana were extracted with hot ethanol. After removal of ethanol,the concentrated ethanol extract was successively extracted with petrol ether( PE),ethyl acetate( Et OAc) and n-butanol( Bu OH) to yield PE,Et OAc and Bu OH fractions.Chemical constituents from the Bu OH fraction wer...