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An ethanol extract of leaves of the plant species Malleastrumsp. collected in northern Madagascar afforded the new clerodane diterpene 18-oxo-cleroda-3,13-dien-16,15-olide (1), together with the three known clerodane diterpenes 16,18-dihydroxykolavenic acid lactone (2), solidagolactone (3) and (-)-kolavenol (4), and the known labdane diterpene 3-oxo-ent-Iabda-8(17),13-dien-15,16-olide (5). Compounds 1, 3, and 4showed moderate antiproliferative activities against the A2780 ovarian cancer cell line, with the IC50values of 3.01 ± 0.8, 7.84 ± 0.2, and 17.9 ± 3 μM, respectively. The structure elucidations of all compounds were carried out based on analysis of NMR and mass spectroscopic data. The relative stereochemistry of compound 1was determined by NOESY NMR spectrum.

As part of the International Cooperative Biodiversity Group (ICBG) program, in a search for antiproliferative compounds, an ethanol extract of Polyscias duplicatawas investigated due to its antiproliferative activity against the A2780 human ovarian cell cancer line (IC506 μg/mL). Seven known oleanane glycosides, 3β-[(α-L-arabinopyranosyl)oxy]-16α-hydroxyolean-12-en-28-oic acid (1, IC508 μM), 3β-[(α-L-arabinopyranosyl)oxy]-16α,23-dihydroxyolean-12-en-18-oic acid (2, IC5013 μM), 3β-[(O-β-D-glucopyranosyl-(1→3)-α-L-arabinopyranosyl)oxy]–16α-hydroxyolean-12-en-28-oic acid (3, IC507 μM), 3β-[(O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl)oxy]-16α-hydroxyolean-12-en-28-oic acid (4, IC502.8 μM), 3β-[(O-β-D-glucopyranosyl-(1→3)-α-L-arabinopyranosyl)oxy]–23-hydroxyolean-12-en-28-oic acid (5, IC5010 μM), 3β-[(O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl)oxy]-23-hydroxyolean-12-en-28-oic acid (6, IC503.4 μM), and 3β-[(α-L-arabinopyranosyl)oxy]-23-hydroxyolean-12-en-28-oic acid (7, IC503.4 μM) were isolated, and their structures determined using spectroscopic methods.

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 Molinaea retusaRadlk. (Sapindaceae) was investigated on the basis of its moderate antiproliferative activity against the A2780 human ovarian cancer cell line (IC5016 μg/mL). One new compound, 2″,3″,4″,6′-de-O-acetylcupacinoside (1, IC5015.4 μM) and two known compounds, cupacinoside (2, IC509.5 μM) and 6-de-O-acetylcupacinoside (3, IC5010.9 μM), were isolated by bioassay-directed fractionation using liquid-liquid partitioning, column chromatography, and HPLC. Compounds 2 and 3 also had moderate antiplasmodial activities, with IC50values of 4.0 and 6.4 μM, respectively, against Plasmodium falciparum, Dd2 strain. The structures were determined using spectroscopic methods.

Antiproliferative bioassay-guided fractionation of the ethanol extract of the endemic Malagasy Rubiaceous plant Tarenna greveiled to the isolation of two new antiproliferative oxygenated oleanane triterpene saponins. The structures of the two active compounds were elucidated as 23-hydroxylongispinogenin 3-O-β-D-glucopyranoside (1) and longispinogenin 3-O-β-D-glucopyranosyl (1→2)-β-D-glucopyranoside (3) by analyses of their spectral data including 1D- and 2D-NMR spectroscopy and chemical evidence. Compounds 1and 3displayed moderate antiproliferative activity against the A2780 ovarian cancer cell line with IC50values of 7.6 and 4 μM, respectively.

Bioassay guided fractionation of the ethanol extract of a new endemic species of the genus Astrotrichilialed to the isolation of the new antiproliferative 3-(4′-hydroxy-2′,3′-dihydroprenyl)-4,6-dimethoxy-5-methylcoumarin, named astrotricoumarin (8) with an IC50value of 6.8 μM against the A2780 cell line. The structure of compound 8was elucidated on the basis of its physical and spectroscopic data, including extensive 1D- and 2D-NMR analysis.