Phyllanthus niruri has a considerable wide usage as a medicinal plant in South Western Nigeria and decoction is one of the forms of preparation. The neutralization of ROS by natural antioxidants helps manage various diseases, arousing interest in natural antioxidants. We therefore examined the antioxidative and HO-1-inducing capacity of the aqueous extract of Phyllanthus niruri (P. niruri). The antioxidant capacity of P. niruri was determined by its ability to scavenge radicals, chelate Fe2+ and inhibit lipid peroxidation. P. niruri was also investigated for its effect on the expression of endogenous antioxidant enzymes in unstressed rats and its ability to induce HO-1 in murine macrophages. HPLC was used also to unveil the phenolic composition of the plant. Some of P. niruri 's phenolic compounds are quercetin, and astragalin. The in vitro antioxidant assays revealed that P. niruri exhibited good radical scavenging capacity. It also inhibited ?-carotene bleaching and lipid peroxidation. The protein levels of the endogenous antioxidant enzymes were significantly higher in the P. niruri -treated group. It also caused a marked increase in the activity of HO-1. P. niruri is effective in scavenging radicals and influencing the expression of endogenous antioxidant enzymes due to its phytoconstituents. It has excellent potential as a natural antioxidant source.

Keywords: Phyllanthus niruri, heme-Oxygenase-1, antioxidants, oxidative stress.