Unripe Carica papaya fruits were extracted with methanol in Soxhlet apparatus and later with a liquid-liquid extraction with the aim of identifying and quantifying secondary metabolite fraction of this plant. Quercetin and β-sitosterol have been isolated from the fruit and the quantities detected were 120.2±0.16 mg/g (dry fruit) and 279.1±0.09mg/g respectively. In addition, the extracts were evaluated in vivo for their effects on activities of some antioxidant enzymes which includes Glutathione peroxidase (GPx), Glutathione reductase (GR), Glutathione transferase (GST), Catalase (CAT) and metabolizing enzyme Glucose-6-phosphate dehydrogenase (G6PDH) in mice treated orally with a daily dose of extracts (100mg/kg) for 7 days. Results showed that ethyl acetate fraction caused significant increase(p<0.05) in the activities of GR, GPx, GST, and G6PDH. Significant decrease (p<0.05) in GPx activity was observed in kidney following administration of ethyl acetate fraction. It is likely that quercetin and β-sitosterol may be responsible for the antioxidant potential demonstrated by the ethyl acetate fraction from unripe fruit.