Ethyl Gallate Isolated from Castanopsis cuspidata var. sieboldii Branches Inhibits Melanogenesis and Promotes Autophagy in B16F10 Cells

Abstract

The Castanopsis cuspidata var. sieboldii (CCS) plant grows predominantly in temperate regions of Asian countries, such as South Korea. Research on CCS has so far concentrated on the nutritional analysis, antioxidant activity, and anti-inflammation properties of its branches. However, the isolation of compounds and structural elucidation of effective single molecules remain unexplored, necessitating further exploration of CCS branches. Therefore, this study demonstrates the antioxidant and antimelanogenic activity of a single substance of ethyl gallate (EG) isolated from CCS branch extracts. Notably, the antimelanogenic (whitening) activity of EG extracted from CCS branches remains unexplored. Tyrosinase inhibition, kinetic enzyme assays, and molecular docking studies were conducted using mushroom tyrosinase in order to examine the antioxidant mechanism and antimelanin activity of EG in B16F10 melanoma cells. Nontoxic EG concentrations were found to be below 5 µg/mL. While EG significantly reduced the levels of whitening-associated proteins, p-CREB, and p-PKA, it dose-dependently inhibited the expression of TYR, TRP-1, TRP-2, and transcription factor (MITF). In addition, EG downregulated melanogenetic gene expression and activated autophagy signals. Therefore, EG extracted from CCS branches could serve as a novel functional cosmetic material with antimelanogenic and autophagy-enhancing activity.

Protective Effect of Castanopsis sieboldii Extract against UVB-Induced Photodamage in Keratinocytes

“…Ascorbic acid, used as a positive control, exhibited an IC 50 of 36.61 ± 1.92 μg/mL in the DPPH assay and 37.37 ± 2.11 μg/mL in the ABTS assay. In addition, we recently identified the antioxidant capacity of five fractions of CSL3 (n-hexane, chloroform, ethyl acetate, n-butanol, and water) and isolated polyphenolic compounds [ 24 ]. Experimental results revealed that EtOAc fractions of CSL3 had the highest radical scavenging activity and contained total polyphenol contents (TPC) and total flavonoid contents (TFC).…”

“…Among them, CSL3 had the highest content of polyphenols with 4264.20 ug/g, followed by CSL1, CSL2, and CSL4 ( Figure S1 ). In our previous study, the components detected in the EtOAc fraction of the CS were high in the order of ethyl gallate, gallic acid, and chlorogenic acid [ 24 ]. However, the content of EGCG was the highest, and gallic acid, protocatechuic acid, and chlorogenic acid were mainly detected in the current study.…”