Hepatoprotective and antioxidative properties of Salacia reticulata: preventive effects of phenolic constituents on CCl4-induced liver injury in mice.

The hepatoprotective effects of the hot water (SRHW) and methanolic (SRM) extracts from the roots and stems of Salacia reticulata were examined using an oxidative stress-induced liver injury model. Both SRHW and SRM extracts (400 mg/kg, p.o.) significantly suppressed the increase in glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) activities in carbon tetrachloride (CCl4)-treated mice. These extracts also inhibited CCl4-induced thiobarbituric acid-reactive substance (TBA-RS) formation, which indicates increased lipid peroxidation in the liver. A good correlation (r=0.945, p<0.01) was observed between the amount of phenolic compounds in the extracts and their inhibitions of TBA-RS formation. The IC50 values of the extracts on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging were less than 10 microg/ml and the antioxidative activities of six phenolic compounds from the roots of S. reticulata were examined. Mangiferin, (-)-4'-O-methylepigallocatechin, and (-)-epicatechin-(4beta-->8)-(-)-4'-O-methylepigallocatechin, which a principal phenolic compounds, showed potent scavenging activity on DPPH radicals and their concentrations required for 50% reduction of 40 microM DPPH radicals were 5.9, 10, and 3.2 microM, respectively. On the other hand, against the CCl4-induced serum GOT and GPT elevations and TBA-RS formation in mice, mangiferin and (-)-4'-O-methylepigallocatechin showed potent activity at a dose of 100 mg/kg, but (-)-epicatechin-(4beta-->8)-(-)-4'-O-methylepigallocatechin did not. These results suggest that the antioxidative activity of the principal phenolic compounds is involved in the hepatoprotective activity of S. reticulata.