Effects of Thymol on Mushroom Tyrosinase-Catalyzed Melanin Formation

Abstract

The novel inhibitory mechanism of thymol (2-isopropyl-5-methylphenol) on dopachrome formation by mushroom tyrosinase (EC 1.14.18.1) was identified. The UV-vis spectrum and oxygen consumption assays showed dopachrome formation using L-tyrosine as a substrate was suppressed by thymol. This inhibitory activity was reversed by the addition of a well-known radical scavenger, butylated hydroxyanisole (BHA). Further investigations using N-acetyl-L-tyrosine as a substrate with HPLC analysis suggested that thymol inhibits chemical redox reactions between dopaquinone and leukodopachrome instead of enzymatic reaction. This redox inhibitory activity of thymol was examined by using a model redox reaction with L-dihydroxyphenylalanine (L-DOPA) and p-benzoquinone. Thymol successfully inhibited oxidation of L-DOPA to dopaquinone, coupled with reduction of p-benzoquinone. Hence, the suppression of dopachrome formation by thymol is due to the inhibition of conversion of leukodopachrome to dopachrome. The antioxidant property of thymol is a key characteristic for the inhibitory mechanism of melanin synthesis.

Tyrosinase inhibitory activity, molecular docking studies and antioxidant potential of chemotypes of Lippia origanoides (Verbenaceae) essential oils

“…Thus, the suppression of the formation of dopachrome by thymol is due to inhibition of leuko-dopachrome to dopachrome conversion. The antioxidant properties of thymol are considered as a key feature to the mechanism of inhibition of melanin synthesis [39]. …”

GC-MS analysis and in vitro antioxidant and enzyme inhibitory activities of essential oil from aerial parts of endemic Thymus spathulifolius Hausskn. et Velen

“…However, Satooka and Kubo 60 reported that thymol was an important inhibitor against tyrosinase in melanogenesis. In this direction, the high level of thymol in the studied essential oil could be responsible of tyrosinase inhibitory activity of the essential oil.…”

Kinetic and in silico studies of novel hydroxy-based thymol analogues as inhibitors of mushroom tyrosinase

“…Liu (2003) and Chen (2005) also reported that alkoxy benzoic acids and hydroxy benzoic acids showed potent mushroom tyrosinase inhibitory activity [13,14]. Thymol a naturally occurring monoterpene phenol which is the main constituent of thyme possesses tyrosinase inhibitory activity [15] along with other numerous pharmacological activities. As phenolic antioxidants, thymol protects food qualities and organisms from damage induced by oxidative stress.…”