CHEMICAL CONSTITUENTS AND CYTOTOXICITY OF PAPHIOPEDILUM EXUL ROOTS

Abstract

Chemical investigation of the roots of Paphiopedilum exul (Ridl.) Rolfe (family Orchidaceae) yielded one new stilbene, (E)-5,6′-hydroxy-3,2′-dimethoxystilbene, and eight known compounds including five stilbenes i.e. (E)-5-hydroxy-3-methoxystilbene, (E)-5-hydroxy-3,2′-dimethoxystilbene, (E)-2-(4″-hydroxybenzyl)-5,2′-dihydroxy-3,5′-dimethoxystilbene, (E)-5,2′-dihydroxy-3,5′-dimethoxystilbene and (E)-2-(4″-hydroxybenzyl)-5-hydroxy-3-methoxystilbene, and three flavonoids i.e. galangin, pinocembrin and alpinetin. The chemical structures of these constituents were identified and elucidated by spectroscopic techniques including UV, IR, MS and NMR, as well as comparison with previously reported data. Cytotoxicity of isolated compounds against KB, NCI-H187 and MCF-7 cell lines was then evaluated by the rezasurin microplate assay (REMA). Their topoisomerase I inhibitory activity was also examined using the yeast cell-based assay.