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Bioactivity-guided fractionation of a chloroform extract of the aerial parts of Baccharis articulata (Lam.) Pers. has led to the isolation of two known compounds that were significantly active against the P-388 lymphocytic leukemia cell line, namely, apigenin and methyl-3-(3,4-dihydroxyphenyl)-2-propenoate. Also obtained were five inactive compounds, comprising three new compounds, 7-oxo-8usd\betausd,16,19-trihydroxy-3,4-dehydro-ent-clerodan-15,20-dicarboxy-dilactone, 15usd\betausd-methoxy-12(17),15(16)-diepoxy-ent-labd-9(11)-ene and cadinane 10,11-peroxide, and two known compounds, 7-oxo-16,19-dihydroxy-3,4-dehydro-ent-clerodan-15,20-dicarboxy-dilactone and genkwanin. Apigenin also exhibited cytotoxicity against melanoma (Mel2, ED{50}, 3.6 mug/ml) and multidrug-resistant KB (ED{50}, 4.2 mug/ml) cells. The potently sweet Baccharis gaudichaudiana constituent, gaudichaudioside A, was not detected in B. articulata extracts. An aqueous methanol extract of B. articulata was found to be bitter rather than sweet, which was determined as being due, in part, to the presence of 7-oxo-16,19-dihydroxy-3,4-dehydro-ent-clerodan-15,20-dicarboxy-dilactone, a bitter-tasting substance. Three new compounds, 2-hydroxy-5-butoxyphenylacetic acid, 2usd\betausd-D-glucopyranosyloxy-5-butoxyphenylacetic acid, and entadamide A 2-O-usd\betausd-D-glucoside, in addition to the new natural product 2,5-dihydroxyphenyl acetic acid methyl ester, have been isolated and characterized from the seeds of Entada phaseoloides (L.) Merr. Three known compounds, entadamide A, phaseoloidin and usd\betausd-sitosterol glucoside were also isolated from the seeds of E. phaseoloides. When evaluated for cytotoxic potential with a battery of cultured human cancer cells, all of the isolates obtained from E. phaseoloides were found to be devoid of cytotoxic activity. However, 2,5-dihydroxyphenylacetic acid methyl ester and 2-hydroxy-5-butoxyphenylacetic acid exhibited significant cytotoxicity against the P-388 cell line. Also active against this cell line were the natural product derivatives 2-hydroxy-5-butoxyphenylacetic acid methyl ester and 2usd\betausd-D-glucopyranosyloxy-5-butoxyphenylacetic acid methyl ester. Activity-guided fractionation of the methanol extract of Fibraurea chloroleuca Miers resulted in the isolation of one major compound, berberine, which in the form of its chloride salt was observed to demonstrate significant cytotoxic activity for P-388 cells (ED{50}, 0.2 mug/ml) as well as several human cancer cell lines ((ED{50}, mug/ml): breast cancer, 1.0; fibrosarcoma, 0.9; KB cells, 3.1). Two other protoberberine alkaloid isolates, berberrubine chloride and thalifendine chloride, were found to exhibit cytotoxic activity against P-388 cells (ED{50}, 0.6 and 0.3 mug/ml, respectively), but not against any of the human cancer cell lines. The phytoecdysteroid isolate, 20-hydroxyecdysone was inactive against all the cell lines employed in this investigation.
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