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Identifying an isoflavone from the root of Pueraria lobata as a potent tyrosinase inhibitor

Wagle, Aditi, Seong, Su Hui, Jung, Hyun Ah, Choi, Jae Sue
Food chemistry 2019 v.276 pp. 383-389
L-dopa, Pueraria montana var. lobata, active sites, computer simulation, daidzein, dose response, enzyme inhibitors, enzymes, ethanol, formononetin, functional foods, inhibitory concentration 50, moieties, mushrooms, tyrosine
Traditionally, the root of Pueraria lobata are widely used as a functional food. It was observed that a 70% ethanol extract showed a dose-dependent inhibition towards mushroom tyrosinase. Among the different isolated compounds, calycosin demonstrated potent inhibitory activity against substrates l-tyrosine and l-DOPA, with IC50 of 1.45 ± 0.03 and 7.02 ± 0.46 µM, respectively. Conversely, formononetin and daidzein exhibit weak inhibition. Moreover, kinetic studies revealed calycosin to be a competitive inhibitor for both substrates. Additionally, molecular docking simulation showed that the hydroxyl groups at C-3′ and C-7 positions interacted with the catalytic site and peripheral residues, demonstrating a higher affinity toward mushroom tyrosinase. Accordingly, our results suggest that, rather than a mono-substituted hydroxyl or methoxyl group, the presence of a hydroxyl group at C-3′ and a methoxyl group at C-4′ position of the isoflavone skeleton plays an essential role in the manifestation of anti-browning activity in food products.