Valonea Tannin: Tyrosinase Inhibition Activity, Structural Elucidation and Insights into the Inhibition Mechanism

Abstract

Valonea tannin is a natural product readily extracted from acorn shells that has been suggested to have potential skin whitening properties. This study investigated the tyrosinase inhibition activity of extracted valonea tannin and the associated structure–function activity. Nuclear magnetic resonance spectroscopy and molecular weight analysis with gel permeation chromatography revealed that valonea tannin could be characterized as a hydrolysable tannin with galloyl, hexahydroxydiphenoyl and open formed-glucose moieties and an average molecular weight of 3042 ± 15 Da. Tyrosinase inhibition assays demonstrated that valonea tannin was 334 times more effective than gallic acid and 3.4 times more effective than tannic acid, which may relate to the larger molecular size. Kinetic studies of the inhibition reactions indicated that valonea tannin provided tyrosinase inhibition through mixed competitive–uncompetitive way. Stern–Volmer fitted fluorescence quenching analysis, isothermal titration calorimetry analysis and in silico molecule docking showed valonea tannin non-selectively bound to the surface of tyrosinase via hydrogen bonds and hydrophobic interactions. Inductively coupled plasma-optical emission spectroscopy and free radical scavenging assays indicated the valonea tannin had copper ion chelating and antioxidant ability, which may also contribute to inhibition activity. These results demonstrated the structure–function activity of valonea tannin as a highly effective natural tyrosinase inhibitor that may have commercial application in dermatological medicines or cosmetic products.

Role of Phytochemicals in Skin Photoprotection via Regulation of Nrf2

“…Gallic acid, gallotannin, valonia tannin and extracts of plants (e.g., Ceylon olive leaves and pomegranate peel) containing gallic acid exerted antimelanogenic effects directly by acting as a competitive inhibitor of tyrosinase and indirectly by inhibiting tyrosinase via antioxidant actions that affect melanogenesis pathway in vitro and in vivo ( Chen et al, 2009 ; Panich et al, 2013 ; Su et al, 2013 ; Kanlayavattanakul et al, 2020 ; Huang et al, 2021 ; Liu et al, 2021 ). A randomized, double-blind, placebo-controlled clinical trial demonstrated that continuous administration of apple polyphenol rich in procyanidins for 12 weeks improved UV-induced skin pigmentation in heathy women ( Shoji et al, 2020 ).…”

Identification of Phenolic Compounds by LC-MS/MS and Evaluation of Bioactive Properties of Two Edible Halophytes: Limonium effusum and L. sinuatum

“…On the other hand, quercetin glycosides, including hyperoside with IC 50 value of 15.67 µg/mL, are accepted as being suitable for anti-melanogenesis purposes with no cytotoxicity [ 43 ]. Tannic acid exerted tyrosinase inhibition (IC 50 value, 4.0 ± 0.01 mM), this effect was attributed its pyrogallol moiety that played a critical role in the enzyme inhibition process [ 44 ]. In addition, a molecular docking study suggested that the catechol moiety of quercetin might chelate copper in the active site of tyrosinase, causing the blocking of access of l -DOPA into the catalytic center.…”

Effect of Tannin Furanic Polymer in Comparison to Its Mimosa Tannin Extract on the Growth of Bacteria and White-Rot Fungi

“…There are several studies that report this observation for many enzymes such as α-amylase, α-glucosidase, glucoamylase, cholinesterase and tyrosinase [ 38 , 39 , 40 , 41 ]. The mechanism occurring is the formation of stable tannin–protein complexes, which hinder the execution of their enzymatic functions [ 42 , 43 ].…”