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Fifty-five triterpenoids consisting of 19 tetracyclic, 32 pentacyclic, and 4 incompletely cyclized triterpenoids, and 2 sterols, mostly isolated from various plant and fungal materials, were examined for their inhibitory effects on a purified human immunodeficiency virus type 1 (HIV-1) reverse transcriptase. Twenty triterpenoids and one sterol showed inhibitory effects with 50% inhibition concentration (IC50) values less than 5.0 microM. Among these cycloartenol ferulate (IC50 = 2.2 microM), 24-methylenecycloartanol ferulate (1.9 microM), lupenone (2.1 microM), betulin diacetate (1.4 microM), and karounidiol 29-benzoate (2.2 microM) inhibited most effectively. Some of the triterpenoids and sterols may be potential new lead compounds to find still more potent HIV-1 reverse transcriptase inhibitors.

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An antitumour-promoting activity in two-stage carcinogenesis, is found in the methanol extract of the Carthami Flos (Carthamus tincton'us L.; Compositae), which is a traditional Chinese medicine and natural pigment of rouge additivies in certain Asian countries. From these active fractions, As-and A'-sterol fractions were separated. The separation was examined for inhibitory activity against TPA-induced inflammatory ear oedema in mice. Stigmasterol (71% in the mixture) was the most abundant of 14 sterols identified in the As-sterol fraction. Schottenol(70% in the mixture) constituted the dominant sterol of the A'-sterol fraction. Furthermore, stigmasterol markedly inhibited tumour promotion in two-stage carcinogenesis experiments.