The In Vivo and In Vitro Antioxidant Effect of the Flavonoid-Rich Fraction of the Methanol Extract of Jatropha Tanjorensis Leaves

Abstract

The leaves of Jatropha tanjorensis are edible and used in herbal medicine in the treatment of diseases associated with oxidative stress. The pharmacological value of the plant is partly associated with its phytochemical components which produce physiological actions in the human body. In the present study, the qualitative and quantitative phytochemical analyses of the crude extract of J. tanjorensis leaves showed the presence of alkaloids (7.00%), flavonoids (20.00%) saponins (2.00%) and tannins (2.30%) while steroids were not detected. The total flavonoid concentration (TFC) of the ethylacetate fraction was 382.601.74 mg QE/g. The flavonoid-rich fraction of J. tanjorensis (FRJT) at various concentrations (0.125 – 1.00 mg/ml) exhibited concentration-dependent increase in total antioxidant capacity (TAC). In the FRAP assay, the reduction of Fe3+ to Fe2+ at different concentrations (15.70-1000 µg/ml) of FRJT was also dose-dependent. There was relative increase in the inhibition (%) of DPPH radicals with increased concentrations (15.70-1000 µg/ml) of FRJT, while the EC50 was 469 µg/ml. The acute toxicity test showed no mortality up to 5 ml/kg (5000 mg/kg) body weight, which indicated the possible safety of FRJT. Assay of antioxidant enzymes (SOD, CAT and GPx) showed that the activities of CAT and GPx were significantly (p ˂ 0.05) lower while that of SOD was found to be non-significantly (p ˃ 0.05) lower in the untreated animals (group 2) when compared to the normal control (group 1). In contrast, SOD activity was found to be significantly (p ˂ 0.05) higher in groups 4 and 5. CAT activity was non-significantly (p ˃ 0.05) higher in groups 3 and 4 whereas GPx activity was found to be significantly (p ˂ 0.05) higher in groups 3 and 4 when compared to the untreated group. There was significant (p < 0.05) elevation in the activities of liver marker enzymes such as AST, ALT and ALP of untreated animals when compared to the normal control. However a significant reduction (p < 0.05) was observed across all the pre-treated groups (Groups 3 - 5) when compared to the untreated group. Serum concentrations of urea and creatinine were found to be significantly (p < 0.05) higher as observed in the untreated group when compared to group 1. Conversely, the concentration of creatinine was significantly (p < 0.05) lower in group 4 and non-significantly (p > 0.05) lower in groups 3 and 5 when compared to the untreated group. The concentration of urea was found to be non-significantly (p < 0.05) lower across all the pre-treated animals (Groups 3 – 5) when compared to the untreated group. PCV, Hb and WBC levels were significantly (p < 0.05) lower in group 2 when compared to group 1. However, supplementation with FRJT and Silymarin ameliorated the induced depletion of blood in the pre-treated animals (Groups 3 - 5). Histological examination of the liver tissue showed marked reduction in fatty degeneration across the pre-treated groups when compared to the untreated group. These results indicate that the flavonoid-rich fraction of J. tanjorensis was able to establish antioxidant effect on in-vitro models. FRJT also exhibited hepatoprotective properties by restoring liver enzymes during CCl4-induced oxidative stress in rat models. These results also indicate that the flavonoid-rich fraction contains antioxidants, which mop up free radicals in the system and support its use in the treatment of diseases resulting from oxidative damage.