Tribuli fructus constituents protect against tacrine-induced cytotoxicity in HepG2 cells.

A new phenolic amide, tribulusimide D (4-hydroxy-N-[3-(4-hydroxy-3-methoxyphenyl)-1-oxo-2-propen-1-yl]-3-methoxybenzamide) (1), together with a known phenolic amide, terrestriamide ((E)-3-(4-hydroxy-3-methoxyphenyl)-N-[2-(4-hydroxyphenyl)-2-oxoethyl]-prop-2-enamide) (2) and a flavonol glycoside, quercetin-3-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranoside (3) were isolated from the H2O extract of Tribuli Fructus. Compounds 1 and 3 showed significant hepatoprotective activities, with EC50 values of 13.46 +/- 0.2 and 7.06 +/- 0.7 microM, respectively, against tacrine-induced cytotoxicity in HepG2 cells.