| Summary: | The aim of the present study was to analyse the peel waste of Xylocarpus granatum fruits as potential source of tyrosinase inhibitors. Dried peel samples were ground to yield a powder (simplicia). Subsequently, they were extracted with organic solvents of distinct polarity levels, namely n-hexane (non-polar), chloroform (semi-polar) and methanol (polar) by use of the single-maceration method. Inhibitory effects on tyrosinase activity (monophenolase) and DOPA auto-oxidation (diphenolase) were determined in bioassays. Assays with the methanol extract revealed IC50 values of 784.87 μg mL-1 (monophenolase) and of 1176.66 μg mL-1 (diphenolase), respectively. In contrast, n-hexane and chloroform extracts showed no activity. These results indicate that the methanolic fruit peel extract contained tyrosinase-inhibiting compounds, such as flavonoids, tannins and saponins, whereas the n-hexane and chloroform extracts yielded alkaloids, steroids and triterpenoids without tyrosinase-inhibiting activity. The phenolic compounds had a strong effect on the tyrosinase enzymes, inhibiting monophenolases by 97% and diphenolases by 96%, with a positive correlation between the total phenolic content and the inhibition rate in both activities.
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