Commonly used tropical medicinal plants exhibit distinct in vitro antioxidant activities against hepatotoxins in rat liver.

Lipid peroxidation in biological systems has been considered as one of the major mechanisms of cell injury in aerobic organisms subjected to oxidation stress. Plants, among other functions, are considered to act as free radical scavengers and as antioxidants. Iron II (Fe(2+)), sodium nitroprusside (SNP) and nitropropionic acid stimulate the production of free radicals and lipid peroxidation. In this study, four commonly used tropical medicinal plants (Kigelia africana, Calotropis procera, Hibiscus sabdariffa and Alchornea cordifolia) were studied (in vitro) for their effects on the formation of thiobarbituric acid reactive substances (TBARS) induced by different pro-oxidants (10 microM FeSO(4), 5 microM -sodium SNP and 2mM 3-nitropropionic acid) in rat liver homogenate. All the pro-oxidants significantly increased (P<0.05) the formation of TBARS, which indicates increased lipid peroxidation in the rat liver (in vitro). However, all the plant extracts statistically (P<0.05) reduced the production of TBARS in a concentration-dependent manner in all the tested pro-oxidant-induced oxidative stresses. Alchornea cordifolia appeared to offer the highest protection. The results of the present study suggest that the use of these plants in the treatment of various diseases, especially liver disease, is probably due to their ability to act as antioxidants.