Potent antihepatotoxic activity of dicaffeoyl quinic acids from propolis.

Hepatoprotective activity guided chemical analyses led to the isolation of two dicaffeoyl quinic acid derivatives, methyl 3,4-di-O-caffeoyl quinate (1) and 3,4-di-O-caffeoyl quinic acid (2) from water extract of propolis, and their structures were determined by the use of 2D NMR. These compounds were stronger antihepatotoxic agents than glycyrrhizin.