In vitro antioxidant activity, inhibitory effect of tyrosinase and DOPA auto-oxidation by Wrightia religiosa extracts

The aerial plant parts of Wrightia religiosa were screened for investigating the invitro antioxidant property, tyrosinase inhibition and anti DOPA auto-oxidation activity by using the ethanolic extraction. The total phenolic, flavonoid and pigment content were assayed. 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging was used to evaluate the antioxidant quality. Moreover, the modified 3,4-dihydroxy-l-phenylalanine (L-DOPA) method was used to determine tyrosinase inhibition activity and anti DOPA auto-oxidation. The results of total phenolic, flavonoid and pigment content screening showed significant difference among the different plant parts of the same species. The content of total phenolic compounds ranged from 0.07 to 1.68 mg GAE/g extract. The total flavonoid concentrations varied from 7.45 to 93.37 mg RUE/g extract. Leaf extract showed the highest antioxidant activity and bark extract, which showed the lowest antioxidant property, exhibited poor tyrosinase inhibition. Petiole extract showed the best tyrosinase inhibition activity and fruit extract showed the best anti-DOPA auto-oxidation, respectively. Both antioxidant and tyrosinase inhibition exhibited a concentration dependence of the extracts. The lowest IC50 of antioxidant, tyrosinase inhibition and anti DOPA auto-oxidation were of leaf, bark and fruit ethanolic extracts (IC50 106.05, 801.73 and 197.21 μg/ml), respectively. These results suggest that W.religiosa showing biological activities may be considered as an alternative constituent for the therapeutic approach in antioxidant and DOPA auto-oxidation treatment.