Alternative Approach for Specific Tyrosinase Inhibitor Screening: Uncompetitive Inhibition of Tyrosinase by Moringa oleifera.

Farah J Hashim,Kanit Vichitphan,Jaehong Han,Sukanda Vichitphan

doi:10.3390/molecules26154576

Farah J Hashim, Kanit Vichitphan + Show 2 more

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https://doi.org/10.3390/molecules26154576

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Abstract

Tyrosinase (TYR) is a type III copper oxidase present in fungi, plants and animals. The inhibitor of human TYR plays a vital role in pharmaceutical and cosmetic fields by preventing synthesis of melanin in the skin. To search for an effective TYR inhibitor from various plant extracts, a kinetic study of TYR inhibition was performed with mushroom TYR. Among Panax ginseng, Alpinia galanga, Vitis vinifera and Moringa oleifera, the extracts of V. vinifera seed, A. galanga rhizome and M. oleifera leaf reversibly inhibited TYR diphenolase activity with IC50 values of 94.8 ± 0.2 µg/mL, 105.4 ± 0.2 µg/mL and 121.3 ± 0.4 µg/mL, respectively. Under the same conditions, the IC50 values of the representative TYR inhibitors of ascorbic acid and kojic acid were found at 235.7 ± 1.0 and 192.3 ± 0.4 µg/mL, respectively. An inhibition kinetics study demonstrated mixed-type inhibition of TYR diphenolase by A. galanga and V. vinifera, whereas a rare uncompetitive inhibition pattern was found from M. oleifera with an inhibition constant of Kii 73 µg/mL. Phytochemical investigation by HPLC-MS proposed luteolin as a specific TYR diphenolase ES complex inhibitor, which was confirmed by the inhibition kinetics of luteolin. The results clearly showed that studying TYR inhibition kinetics with plant extract mixtures can be utilized for the screening of specific TYR inhibitors.

Highlights

Treatment of skin disorders such as melasma, freckles, dark spots and hyperpigmentation is of great importance in the development of pharmaceutical and cosmetic products
Aas long as effective uncompetitive inhibition is screened, investigation of the enzyme inhibition kinetics of plant mixtures can be an efficient approach for the development of specific TYR inhibitors due to the guaranteed safety of plant extracts
The results showed that M. oleifera, V. vinifera and A. galanga exhibited strong inhibition against TYR diphenolase, even compared with ascorbic acid and kojic acid, which are renowned TYR inhibitors

Summary

Introduction

Treatment of skin disorders such as melasma, freckles, dark spots and hyperpigmentation is of great importance in the development of pharmaceutical and cosmetic products. The main cause of these problems is due to the accumulation of large amounts of melanin, produced by melanogenesis of melanosomes in the keratinocytes of the epidermis. Melanogenesis occurs as a protective mechanism of the skin from UV exposure, unusual melanin stimulation produces free radicals causing wrinkles and damage to skin cell integrity [1]. Tyrosinase (TYR) is known as a key enzyme in the controlling step of the melanogenesis pathway [2]. The first reaction is known as monophenolase because L-tyrosine is oxygenated to L-dihydroxyphenylalanine (L-DOPA). The second reaction, diphenolase, oxidizes L-DOPA to L-dopaquinone (Figure 1) [4]. The catalytic study of TYR has been studied with various substrates to measure monophenolase and diphenolase activities [5]. L-DOPA was used as the substrate to investigate the inhibition kinetics of various plant extracts during dopachrome production

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