Fractionation using supercritical CO2 influences the antioxidant and hepatoprotective activity of propolis against liver damage induced by tert-butyl hydroperoxide

Abstract

The ethanolic extract (E) of propolis was further fractionated with supercritical CO2 into four fractions (R, F1, F2 and F3). The extracts and the four fractions were characterised in terms of antioxidant and hepatoprotective activity against tert-butyl hydroperoxide (t-BHP)-induced damage in vitro and in a rat model. The in vitro study revealed that pre-treatment with propolis extract or its fractions significantly protected the primary hepatocytes against damage by t-BHP (P < 0.05). The hepatoprotective capacity increased with the dose of propolis. The R and F1 fractions had the highest flavinoid contents and most effectively protected the liver from damage by t-BHP. This study also demonstrated that the oral pre-treatment with propolis (50 and 100 mg kg−1) 5 days before a single dose of t-BHP (1.5 mm kg−1, s.c. injection) was administered significantly kept the serum levels of hepatic enzyme markers (aspirate aminotransferase and alanine aminotransferase) low, even after treatment with t-BHP (P < 0.05). A pathological examination showed that lesions of liver were partially protected by treatment with propolis extract and fractions. Oxidative stress induced by t-BHP led to lipid peroxidation (malondialdehyde) and changes in the levels of the antioxidant enzymes. However, all the fractions, except F3 at low concentration (50 mg kg−1), markedly suppressed lipid peroxidation and any increase in the activity of antioxidant enzymes.