Antioxidant and Hepatoprotective Activities of Flavonoids from Bauhinia hookeri

In a previous study, the total ethanol extract of Bauhinia hookeri showed a significant hepatoprotective effect in CCl4-induced toxicity model in mice. However, the active components responsible for the activity were not identified. Therefore, this study was undertaken to determine if the activity of B. hookeri extract is due to its flavonoid content. The hepatoprotective activity of B. hookeri flavonoids was determined by measuring the activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in the culture medium of HepG2 cells challenged with CCl4. The lipid peroxidation and antioxidant parameters, superoxide dismutase (SOD) and glutathione (GSH) were estimated in the cell lysates. The isolated flavonoids were identified by mass, UV and NMR spectral data. This study revealed that B. hookeri flavonoid fraction and its pure compounds (kaempferol 3-O-beta-D-glucoside, quercetin 3-O-beta-D-glucoside and catechin 3-O-alpha-L-rhamnoside) possess a promising hepatoprotective activity as evidenced from the normalized levels of ALT and AST. This was attributed partly to their potent antioxidant activity as demonstrated by the increased GSH levels, SOD activity and reduced lipid peroxidation. The whole flavonoid fraction showed the highest cytoprotective activity and was more effective than silymarin. This study highlights a promising natural hepatoprotective remedy derived from B. hookeri.