Chemical constituents from Oldenlandia diffusa and their cytotoxic effects on human cancer cell lines.

Oldenlandia diffusa is an important Chinese traditional medicine with various biological activities such as anti-tumor, anti-inflammatory, anti-oxidant, antibacterial, neuroprotective and hepatoprotective effects. During our course of finding novel compounds from O. diffusa, two new alternariol derivatives named 9-O-(trans-p-coumaroyl)-alternariol (1), 9-O-(trans-caffeoyl)-alternariol (2), together with six known compounds (3-8) were isolated. Their structures were established on the basis of spectroscopic and physicochemical analysis. All isolates were evaluated for in vitro cytotoxic activities on MCF-7, HepG2, A549 and A2780 cancer cells. As a result, new compounds 1 and 2 exhibited potent cytotoxic activities on A2780 cancer cells with IC50 values of 3.1 and 9.4 μM, respectively. And a conclusion was deduced that the p-coumaroyl or caffeoyl moiety could greatly increased the cytotoxic activity of alternariol on cancer cells.