The effect of methanol extracts of tsao-ko (Amomum tsao-ko Crevost et Lemaire) on digestive enzyme and antioxidant activity in vitro, and plasma lipids and glucose and liver lipids in mice.

Our previous study showed that tsao-ko intake can lower plasma and liver triacylglycerol (TG) concentrations and has hypoglycemic and antioxidant activity in mice. This study involved separating two major fractions (A and B) from the methanol extracts (MeX) of tsao-ko using silica gel column chromatography, and then determining the effect of the fractions in vivo and in vitro to clarify the most effective components of tsao-ko. An intake of MeX and A fraction statistically significantly reduced body lipids and plasma thiobarbitutic acid reactive substances (TBARS) concentrations compared with the control and inhibited lipase and alpha-glucosidase activities. These reductions were not observed in mice fed the B fraction and these inhibitions of B fraction were mild compared with MeX and A fraction. The plasma and liver TG concentrations of each fraction group did not show significant differences compared with the control. The [M-H](+) and maximum UV absorption of the A fraction were 291 m/z and 279 nm, respectively. The peak of A fraction appeared at a similar time to the epicatechin standard in the LC/MS/MS analysis and the MS/MS spectrum of the A fraction was similar to that of the epicatechin standard. It was concluded that the most effective component of tsao-ko for body lipid reduction and hypoglycemic and antioxidant activity was contained in the polar fraction and the evidence suggested that this component could be epicatechin. However, the strongest TG lowering components of tsao-ko may be methanol insoluble.