Thesis (M.Sc.)--Chulalongkorn University, 1999

From the preliminary screening test, the methanolic crude extracts of stems and leaves of Hibiscus tiliaceus Linn. exhibited the significant cytotoxic activity against brine shrimp (Artemia salina Linn.). Eight substances were isolated from the crude extract and were identified as a mixture of long chain esters, a mixture of friedelin and friedelan-3 sigma-o1, a mixture of long chain carboxylic acids, a mixture of campesterol, sigma-sitosterol and stigmasterol, 2,5-dimethoxy-1,4-benzoquinone, 5-hydroxy-7,8-dimethoxy coumarin, 5-hydroxy-3,7-dimethoxyflavone and 5-hydroxy-3,3,4,5,7-pentamethoxyflavone. The separation of the crude extract of the leaves of H. tiliaceus afforded six substances. Their structures were characterized as a mixture of friedelin and friedlan-3 sigma-ol, sigma-amyrin, lupeol, p-methoxycinnamic acid, gossypol and vanillic acid. The results of brine shrimp cytotoxicity test indicated that 2,5-dimethoxy-1,4-benzoquinone. 5-hydroxy-3,7-dimethoxyflavone, 5-hydroxy-3,3,4,5,7-pentamethoxyflavone, p-methoxycinnamic acid and gossypol displayed high cytotoxic activity on brine shrimp lethality assay.