Natural and semi synthetic anti-tyrosinase agent from phaleria macrocarpa (scheff.) boerl using ultrasonicassisted extraction

Abstract

Hyperpigmentation disorders cause several aesthetic issues such as melasma, lentigo and sunburn. Tyrosinase enzyme is described as the key limiting enzyme responsible in regulating melanin production. Hence, to prevent hyperpigmentation disorders, the key approach is to control tyrosinase activity. However, several natural whitening agents such as hydroquinone and kojic acid are toxic. Therefore, much effort has been devoted to develop safe and efficient anti-tyrosinase agents. Phytochemical investigation of Phaleria macrocarpa (Scheff.) Boerl led to the isolation of three compounds identified as stigmasterol, mangiferin, and phalerin. Phalerin was identified as the major component and a benzophenone derivative which has been speculated to possess anti-tyrosinase activity. Herein, phalerin was structurally modified by removing methoxyl and glucose moiety to yield (2, 6-dihydroxy-4-methoxyphenyl) (4-hydroxyphenyl) methanone (DHM) and (2, 4, 6-trihydroxyphenyl) (4-hydroxyphenyl) methanone (THM), respectively. The compounds were identified using modern spectroscopic method and evaluated in terms of their antioxidant and tyrosinase inhibitory activities. 2,2-diphenyl-1-picrylhydrazyl assay reveals that THM was the most potent pro-antioxidant followed by mangiferin and DHM with IC50 values of 7.02, 11.30 and 11.50 µM, respectively. Similarly, melanogenesis inhibition assays using 3-isobutyl-1-methylxanthine-stimulated B16F1 melanoma cells shows that THM markedly inhibited tyrosinase activity in dose dependent manner and even stronger than kojic acid which acts as the positive control. In contrast, mangiferin moderately inhibited mushroom tyrosinase in cell free system as well as intracellular tyrosinase activity in B16F1 cells. Collectively, the results indicate that removal of glucose and methoxyl moiety from benzophenone aglycone could enhance tyrosinase inhibition which is in agreement with structure activity relationship that has been reported previously. Evidently, THM is a stronger indirect tyrosinase inhibitor than its aglycone and kojic acid as the positive control while mangiferin displayed moderate inhibitory activity. Both compounds show neutral toxicity against B16F1 melanoma cells. Optimization of phalerin extraction using ultrasonic assisted extraction (250 W with a frequency of 40 kHz) revealed that solvent ratio of 71 % of methanol:water, extraction temperature of 50 ºC and solid to solvent ratio of 1:45 g/mL are the optimum condition to extract phalerin (4.26 mg/g). The results in this study were supported by scanning electron microscope analysis insinuated that the proposed condition is cost effective and a green technique to intensify phalerin yield as compared to the conventional methods of hot and cold maceration. These data are valuable and could be useful to extract phalerin in industrial scale. In addition, the findings also show that the artificial neural network exhibited better predictive capability than response surface methodology.