ABSTRACT
Bakuchiol is gaining major interest for treatments against skin photoaging. The kinetics of mushroom tyrosinase inhibition by bakuchiol, by real-time oxygen sensing and UV-vis monitoring (475 nm), showed competitive inhibition with average Ki constant (µM, 30 °C, pH 6.8) of 6.71 ± 1.23 and 1.15 ± 0.34 for monophenolase and diphenolase reactions respectively, with respective IC50 37.22 ± 5.18 and 6.91 ± 0.96 â¼ at 1 mM substrate, compared to kojic acid IC50 34.02 ± 5.51 and 16.86 ± 3.28 µM. Fluorescence quenching showed a single binding mode with formation constant Ka 1.02 × 106 M-1. The antioxidant activity was studied by inhibited autoxidation of styrene and cumene (PhCl, 30 °C) affording inhibition constant kinh = 18.1 ± 6.6 (104M-1s-1, 30 °C) and of MeLin in Triton™ X-100 micelles giving kinh = 0.16 ± 0.03 (104M-1s-1, 37 °C). Stoichiometric factor was 1.9 ± 0.1. ReqEPR spectroscopy afforded the BDE(OH) as 81.7 ± 0.1 kcal/mol. Bakuchiol is a potent tyrosinase inhibitor with good antioxidant activity having major potential as natural food preservative against oxidation and food-browning.
