Isoetin 5′-methyl ether, a cytotoxic flavone from Trichosanthes kirilowii

Abstract

Bioassay-directed fractionations of the seed extracts of Trichosanthes kirilowii, have resulted in the isolation of two new compounds, 2-(4-hydroxy-3-methoxyphenyl)-3-(2-hydroxy-5-methoxyphenyl)-3-oxo-1-propanol (2) and isoetin 5′-methyl ether (5,7,2′,4′-tetrahydroxy-5′- methoxyflavone) (3), together with two known compounds, 7-hydroxychromone (1) and 5,7,4′-trihydroxy-3′,5′-dimethoxyflavone (tricin, 4). Their structures were characterized by spectroscopic analysis such as 2D-NMR, HRTOFMS, and UV. Compound 3 showed cytotoxicity against human lung cancer cell line A549, human skin melanoma SK-Mel-2, and mouse melanoma B16F1, with IC 50 of 0.92, 8.0, and 7.23 μg/mL, respectively.