Kinetic Characterization of Tyrosinase-catalyzed Oxidation of Four Polyphenols

Abstract

Phenolic compounds such as chlorogenic acid, cryptochlorogenic acid, neochlorogenic acid and caffeic acid are widely distributed in fruits, vegetables and traditional Chinese medicines with a wide range of biological activities. Tyrosinase plays a critical role in the food industry, but recent studies have proposed unexplored aspects of clinical application. Tyrosinase-catalyzed oxidation of four polyphenols as well as its underlying mechanism remains unclear. In the current work, we investigated the kinetic properties of tyrosinase-catalyzed oxidation of the four polyphenols of interest. To measure the unstable o-quinone products, an analytical method using 3-methyl-2-benzothiazolinone hydrazone (MBTH) was established. The optimal incubation time, buffer pH, temperature and enzyme concentration for the enzyme activity in the presence of each polyphenol of interest were investigated. Under the final optimized conditions, the kinetics and substrate specificity of four polyphenols were examined. Kinetic data showed that tyrosinase had the greatest substrate affinity to chlorogenic acid compared with its isomers and caffeic acid. The catalytic efficiency with chlorogenic acid was 8-to 15-fold higher than that with the other 3 polyphenols. Molecular docking study demonstrated that the tight binding of chlorogenic acid at the peripheral site should be the major reason for the specificity to chlorogenic acid. In light of this, the rational design of high-affinity inhibitors against tyrosinase may focus on the binding of both the Cu site and peripheral site. This study will supply a basis for the selection of phenolic acids in food industry and health care.

Optimization, Metabolomic Analysis, Antioxidant Potential and Depigmenting Activity of Polyphenolic Compounds from Unmature Ajwa Date Seeds (Phoenix dactylifera L.) Using Ultrasonic-Assisted Extraction

“…Melanogenesis, the process of melanin production, plays a crucial role in skin pigmentation and can be implicated in various skin conditions [12]. Mushroom tyrosinase is a well-established enzyme used to test compounds that inhibit melanogenesis [51] and the results indicated that UMS significantly suppressed mushroom tyrosinase activity in a concentration-dependent manner, with a lower IC 50 value (48.60 ± 1.02 µg/mL) compared to the positive control, arbutin (IC 50 = 131.03 ± 2.01 µg/mL) (Figure S4).…”