The protective potential and possible mechanism of Phyllanthus amarus Schum. & Thonn. aqueous extract on paracetamol-induced hepatotoxicity in rats

The hepatoprotective potential of Phyllanthus amarus Schum. & Thonn. was studied on paracetamolinduced hepatotoxicity in rats by measuring the levels of serum transaminase (SGOT and SGPT), alkaline phosphatase (ALP) and bilirubin, as well as by histopathological examination of the liver. Furthermore, the hepatoprotective mechanisms were investigated by determining the amount of paracetamol and its metabolites (glucuronide, sulfate, cysteine and mercapturic acid conjugates) in urine and pentobarbital-induced sleeping time to indicate the inhibition on cytochrome P450. The involvement of glutathione was evaluated by determining hepatic reduced glutathione. Its radical scavenging activity, iron chelating activity and total phenolic content were also determined. P. amarus aqueous extracts (0.8, 1.6 or 3.2 g/kg) were orally administered twice daily for 7 days prior, for 2 days after, or for 7 days prior and followed by 2 days after a single oral dose of paracetamol (3 g/kg). The results showed that the extract at the doses of 1.6 and 3.2 g/kg decreased the paracetamol-induced hepatotoxicity as indicated by the decrease in SGOT, SGPT, bilirubin and histopathological score while the ALP did not change. Moreover, it is suggested that the hepatoprotective mechanism of this plant was related neither to the inhibition on cytochrome P450, nor to the induction on sulfate and/or glucuronide conjugation pathways of paracetamol, but partly due to the protective effect on the depletion of hepatic reduced glutathione and also its antioxidant activity, especially the radical scavenging and iron chelating activity, which might be related to the high polyphenolic contents. These results support the value of P. amarus, which has been used in Thai folk medicine for the treatment of liver diseases