In vitro antioxidant and anti-inflammatory activities of methanol extract of Vitellaria paradoxa seed (shea seed)

Abstract

Vitellaria paraodoxa (shea tree) is the source of shea seed from which the well-known shea butter is derived. The methanol extract of shea seed was evaluated for its anti-inflammatory and antioxidant activities using diclofenac sodium and ascorbic acid as standard respectively in in vitro methods. The anti-inflammatory activity was determined by inhibition of protein denaturation of bovine serum albumin (BSA) and erythrocyte membrane stabilization of human red blood cell. The antioxidant activity was evaluated using 1, 1-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), thiobarbituric acid reactive substances (TBARS) and total antioxidant capacity (TAC) assays. The results showed that methanol extract of V. paradoxa seed at different concentration protects the heat induced protein denaturation with the maximum percentage inhibition of 27% (IC50=303.0 µg/mL, p<0.05) at 500µg/mL compared to the standard drug which induced maximum inhibition of 45% (IC50=261.4 µg/mL, p<0.05) at 500 µg/mL and the control. The percentage inhibition of the methanol extract and standard drug in erythrocyte stabilization assay increased in a concentration dependent manner with maximum inhibitory activity of 96.9% (IC50=31.47 µg/mL, p<0.05) and 95% (IC50=33.89 µg/mL, p<0.05) at 2000 µg/ml respectively, which indicates that methanol extract stabilized erythrocyte membrane against hypotonic induced hemolysis in a blood sample better than the standard drug. The maximum percentage inhibition of methanol extract and standard drug in DPPH assay were found to be at 97% (IC50=8.95 µg/mL, p<0.05) and 98% (IC50=6.72 µg/mL, p<0.05) respectively at 100 µg/ml. The absorbance of the reductive capacities in FRAP assay indicates that the methanol extract has higher reducing potency in a concentration dependent manner. The methanol extract exhibited total antioxidant capacity of 0.25 ± 0.04 µg/(AAE/g) when compared to the standard drug 0.87 ± 0.03 µg/(AAE/g) at highest concentration of 100 µg/ml. For TBARS assay, low absorbance value indicate a high level of inhibition of lipid peroxidation. The maximum percentage inhibition of methanol extract was 97.5 % (IC50=51.79 µg/mL, p<0.05) and ascorbic acid was 99% (IC50=52.30 µg/mL, p<0.05) at concentration of 20 µg/ml. The assay indicates that the methanol extract has higher inhibiting potency in a reverse concentration dependent manner. In conclusion, V. paradoxa seed may possess strong anti-inflammatory and antioxidant activities which could constitute a potential source for development of new therapy.