Antiproliferative compounds of Helmiopsis sphaerocarpa from the Madagascar rainforest†

^†Biodiversity Conservation and Drug Discovery in Madagascar, Part 33. For part 32, see Hou et al. (2008).

Abstract

Bioassay-directed separation of an ethanol extract of the leaves of Helmiopsis sphaerocarpa L.C. Barnett (Sterculiaceae) led to the isolation of the new compound 14α,15α-epoxy-3β-hydroxytaraxerane (1) and the four known compounds taraxerol (2), stigmast-5-en-3-ol (3), 5α,8α-epidioxy-24(S)-methylcholesta-6,22-dien-3β-ol (4), and 24ξ-hydroperoxy-24-ethylcholesta-4,28(29)-dien-3-one (5). The structure of the new compound 1 was established on the basis of interpretation of its 1D and 2D NMR spectroscopic data. All the compounds were tested against A2780 human ovarian cancer cell lines, and compounds 4 and 5 showed mild antiproliferative activity, with IC₅₀ values of 16 and 7 µg mL⁻¹, respectively.

^†Biodiversity Conservation and Drug Discovery in Madagascar, Part 33. For part 32, see Hou et al. (2008).

Keywords:

• Helmiopsis sphaerocarpa
• Sterculiaceae
• taraxerane
• NMR
• antiproliferative activity

Acknowledgements

This project was supported by the Fogarty International Center, the National Cancer Institute, the National Science Foundation, the National Heart, Lung and Blood Institute, the National Institute of Mental Health, the Office of Dietary Supplements and the Office of the Director of NIH, under Cooperative Agreement U01 TW000313 with the International Cooperative Biodiversity Groups, and this support is gratefully acknowledged. We thank Dr M. Callmander (Missouri Botanical Garden, Antananarivo) for assistance with the plant description, and Mr B. Bebout and Mr T. Glass (Virginia Polytechnic Institute and State University) for obtaining the mass spectra and for assistance with the NMR spectra, respectively. Field work essential for this project was conducted under a collaborative agreement between the Missouri Botanical Garden and the Parc Botanique et Zoologique de Tsimbazaza and a multilateral agreement between the ICBG partners, including the Centre National d’Applications des Recherches Pharmaceutiques. We gratefully acknowledge courtesies extended by the Government of Madagascar (Ministère des Eaux et Forêts).

Notes

^†Biodiversity Conservation and Drug Discovery in Madagascar, Part 33. For part 32, see Hou et al. (2008).