Phytochemical investigation of Adenium obesum Forskal (Apocynaceae): isolation and identification of cytotoxic agents.

An ethanol extract of Adenium obesum exhibited cytotoxic activity against the human epidermoid carcinoma of the nasopharynx test system. Constituents in the active extract were identified as the cardenolides somalin, hongheloside A, 16-acetylstrospeside, and honghelin and the flavonol 3,3'-bis(O-methyl)quercetin. Their identities were proven by IR, UV, proton magnetic resonance, and mass spectrometry; elemental analyses; preparation of derivatives; and melting-point determinations. An inactive triterpene, dihydroifflaionic acid, and an inactive flavonol, 3-O-methylkaempferol, also were isolated and identified.