Plant anticancer agents XLIV. Cytotoxic constituents from Stizophyllum riparium

Bioactivity-guided fractionation of a CHCl3 extract of Stizophyllum riparium has afforded six new compounds, namely, the triterpene esters, 3 beta-hydroxy-24-transferulyloxyurs-12-en-28-oic acid, 3 beta-hydroxy-24-cis-ferulyloxyurs-12-en-28-oic acid, 3 beta, 19-dihydroxy-24-trans-ferulyloxyurs-12-en-28-oic acid, and the pregnane derivatives, 2 alpha, 3 beta, 12 beta-trihydroxypregna-4,7,16-trien-20-one, 2 alpha, 3 beta, 12 beta-trihydroxypregna-4,7-dien-20-one, and 16 alpha-methoxy-2 alpha, 3 beta, 12 beta-trihydroxypregna-4,7-dien-20-one. The structures of these isolates were established by spectroscopic and chemical methods. Compounds 1, 2, and 4 exhibited cytotoxic activity against the P-388 lymphocytic leukemia test system in cell culture.