The Effect of Polyphenolic Extracts from 10 New Zealand Kiwifruit Cultivars in Inhibiting Tyrosinase Enzyme Activity In vitro.

Objective: The aim of this study was to assess the ability of polyphenolic extracts from different kiwifruit genotypes to affect tyrosinase enzyme activity and determine potential relationships between tyrosinase inhibition and polyphenolic composition. To date, research on the tyrosinase inhibitory bioactivity of kiwifruit have focused on a single A. chinensis cultivar. Given the numerous genotypes of kiwifruit commercially grown have varying compositions, and a variety of polyphenolic compounds present within each of these cultivars, the full potential of the tyrosinase inhibitory of kiwifruit has not been fully evaluated. Methods: The polyphenolic composition of ethanol extracts from the cortical flesh of 10 kiwifruit genotypes was characterized using high-resolution accurate mass liquid chromatography mass spectrometry. The tyrosinase activity of each extract was measured spectrophotometrically in vitro. Multivariate analysis was subsequently conducted to identify kiwifruit compounds that may correlate with tyrosinase enzyme inhibition. Results: The kiwifruit extracts displayed a broad range of tyrosinase inhibitory activity with some extracts having minimal or no inhibitory effect while the most potent extract showed 33.54 ± 1.59% inhibition (P < 0.01) at a dose of 125 µg/mL. Multivariate analysis of polyphenolic and tyrosinase inhibition data identified that polymeric procyanidins likely explain the tyrosinase inhibitory ability and the differences between genotypes. This was confirmed by the high relative concentrations of these procyanidins in extracts that exhibited tyrosinase inhibitory properties, while being absent or at low concentrations in extracts that did not. Conclusion: Our findings demonstrate that some polyphenol kiwifruit extracts inhibit tyrosinase activity. The variability in the tyrosinase inhibitory activity of polyphenol extracts from 10 kiwifruit genotypes is attributed to the differences in the relative concentrations of polymeric procyanidins in these extracts. These results highlight that the tyrosinase inhibitory properties of kiwifruit genotypes could be examined further to support the development of kiwifruit-based cosmetic products. [ABSTRACT FROM AUTHOR]