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A New Bioactive Diterpene Glycoside from Molinaea retusa
In a continuing collaboration in a search for new antiproliferative compounds in Madagascar as part of an International Cooperative Biodiversity Group (ICBG), an ethanol extract of Molinea retusa Radlk. was investigated on the basis of its moderate antiproliferative activity against the A2780 human ovarian cell cancer line (IC50 16 µg/mL). One new compound, 2'',3'',4'',6'-de-O-acetylcupacinoside (1, IC50 15.4µM) and two known compounds, cupacinoside (2, IC50 9.5µM) and 6-de-O-acetylcupacinode (3, IC50 10.9µM), were isolated by bioassay-directed fractionation using liquid-liquid partitioning, column chromatography, and HPLC. Compounds 2 and 3 also had moderate antiplasmodial activities, with IC50 values of 4.0 and 6.4µM, respectively, against Plasmodium falciparum. The structures were determined using spectroscopic methods.