Phlorotannins with Potential Anti-tyrosinase and Antioxidant Activity Isolated from the Marine Seaweed Ecklonia stolonifera.

Manandhar Manandhar,Choi Choi,Wagle Wagle,Kim Kim,Jung Jung,Paudel Paudel,Seong Seong

doi:10.3390/antiox8080240

Manandhar Manandhar, Choi Choi + Show 5 more

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https://doi.org/10.3390/antiox8080240

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Abstract

Compounds were isolated from Ecklonia stolonifera Okamura, a marine brown alga widely consumed as food. Among the isolated compounds, 974-A was demonstrated for the first time to be a potent competitive inhibitor of mushroom tyrosinase activity towards l-tyrosine and l-DOPA (IC50 values = 1.57 ± 0.08 and 3.56 ± 0.22 µM, respectively). Molecular docking simulations clarified that the hydroxyl residues of the isolated compounds formed hydrogen bonds with residues at the catalytic and allosteric sites of tyrosinase, while other residues participated in hydrophobic interactions. Moreover, 974-A, phlorofucofuroeckol-A and eckol reduced the cellular melanin content and tyrosinase activity, and downregulated the expression of melanogenesis enzymes including tyrosinase, tyrosinase-related protein (TRP)-1, and TRP-2 in B16F10 melanoma cells. These compounds also effectively scavenged radicals at the cellular level. Thus, our results revealed that compounds isolated from E. stolonifera are potent tyrosinase inhibitors with potential applications in the cosmetic industry for treatment of hyperpigmentation and for the anti-browning effect in the agricultural field.

Highlights

Tyrosinase has become an enzyme of concern due to its roles in both the melanogenesis of mammals and the enzymatic browning of fruits and fungi
Inhibitory Activities of Compounds Isolated from E. stolonifera against Mushroom Tyrosinase
The previous investigators only determined the inhibitory activity with l-tyrosine as a substrate, while we evaluated the activity with both l-tyrosine and l-DOPA as substrates

Summary

Introduction

Tyrosinase has become an enzyme of concern due to its roles in both the melanogenesis of mammals and the enzymatic browning of fruits and fungi. Melanogenesis is initiated with the oxidation of tyrosine to dopaquinone, which is catalyzed by tyrosinase (TYR). This is the rate-limiting step in melanin synthesis, as the subsequent reactions can proceed spontaneously at physiological pH values [2]. Tyrosinase-related protein-1 (TRP-1) and TRP-2 or dopachrome tautomerase play an imperative part in all eumelanin-yielding reactions. TRP-1 has been proposed to increase the eumelanin: pheomelanin ratio [3], whereas TRP-2 mediates the tautomerization of l-dopachrome (a red melanin precursor) to the colorless dihydroxyindole-2-carboxylic acid (DHICA). In the absence of TRP-2, l-dopachrome is spontaneously converted to the toxic melanin precursor, dihydroxyindole (DHI). TRP-2 may protect melanocytes against cytotoxicity by limiting DHI formation [4]. TRP-1 protects against oxidative stress via the peroxidase effect [3]

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