Cytotoxic constituents of the roots of Ekmanianthe longiflora

Bioactivity-directed fractionation of the CHCl3 extract Of the roots of Ekm anianthe longiflora resulted in the isolation of three new natural products , (2R,3R,4R)-3,4-dihydro-3,4-dihydroxy-2-(3-methyl-2-butenyl)-1(2H)-naphtha lenone (I), (2S,3R,4R)-3,4-dihydro-3,4-dihydroxy-2-(3-methyl-2-butenyl)-1(2 H)-naphthalenone (2), and (2R*,3aR*,9R*,9aR*)-9-hydroxy-2-(1-hydroxy-1-meth ylethyl)naphtho[2,3-b]furan-4-one (3), together with the known compounds 2- (1-hydroxyethyl)naphtho[2,3-b]furan-4,9-quinone (4), 2-acetylnaphtho[2,3-b] furan-4,9-quinone (5), dehydro-iso-alpha-lapachone (6), alpha-lapachone (7) , catalponol, and epi-catalponol. The structures of 1-3 were determined usi ng a combination of NMR spectroscopic techniques, and the absolute configur ations of compounds 1 and 2 were obtained using Mosher ester methodology. C ompounds 4-6 showed significant cytotoxicity in a panel of human cancer cel ls. alpha-Lapachone (7) exhibited only marginal activity, and catalponol an d epi-catalponol were inactive in this regard. When tested at 72 mg/kg/inje ction in an in vivo mouse P-388 leukemia system, compound 4 was inactive (1 10% T/C).