Presentation Information
[P03-334]Synthesis and Biological Evaluation of Novel Protocatechuic Acid Alkyl Esters as Potent Dual-Functional Agents for Skin Whitening and Antioxidant Protection
○Se Won Bae1, Yunseul Park1, Suwan Oh1 (1. Kongju National University (Korea))
Keywords:
Protocatechuic Acid Derivatives,Melanogenesis,Antioxidant,Tyrosinase,Cosmeceuticals
[Purpose] Protocatechuic acid (PCA) is a naturally occurring phenolic compound widely recognized for its anti-inflammatory and antioxidant activities. However, its application in topical cosmeceuticals is often limited by its hydrophilic nature, which restricts skin permeability and cellular uptake. The primary objective of this study was to design and synthesize a series of lipophilic PCA alkyl ester (PAE) derivatives to enhance bioavailability. Furthermore, we aimed to systematically evaluate their dual-functional potential as skin-whitening and antioxidant agents by investigating their effects on melanogenesis in B16F10 melanoma cells and oxidative stress in HS68 fibroblast cells.
[Method] A series of PAE derivatives with varying alkyl chain lengths were synthesized via Steglich esterification using dicyclohexylcarbodiimide and 4-dimethylaminopyridine. The chemical structures were confirmed using H-NMR spectroscopy. To assess skin-whitening potential, B16F10 cells were stimulated with α-melanocyte-stimulating hormone (α-MSH), and the inhibitory effects on melanin content and cellular tyrosinase activity were measured. Western blot analysis was performed to examine the expression of key melanogenic proteins, including microphthalmia-associated transcription factor (MITF), tyrosinase, TRP-1, and TRP-2. Antioxidant capacities were evaluated using DPPH and ABTS radical scavenging assays, and cytoprotective effects against oxidative stress were assessed in HS68 fibroblasts.
[Results] The PAE derivatives were successfully synthesized with confirmed structures. In biological assays, the derivatives exhibited low cytotoxicity in both B16F10 and HS68 cell lines. Regarding whitening activity, PAEs significantly inhibited α-MSH-induced melanin accumulation and tyrosinase activity in a dose-dependent manner, demonstrating superior efficacy compared to the parent PCA. Western blotting revealed that PAEs effectively downregulated the protein expression of MITF, Tyrosinase, TRP-1, and TRP-2. Additionally, in antioxidant assays, the derivatives retained potent radical scavenging activities comparable to L-ascorbic acid and successfully protected HS68 fibroblasts from oxidative stress-induced cell death.
[Consideration] The superior biological activity of PAEs compared to PCA is likely attributed to the increased lipophilicity conferred by the alkyl ester chains, which facilitates enhanced cellular membrane permeability. The significant downregulation of MITF and downstream melanogenic enzymes suggests that the depigmenting mechanism of PAEs involves the modulation of the cAMP/PKA/CREB signaling pathway. Importantly, the structural modification at the carboxyl group did not compromise the antioxidant capacity derived from the catechol moiety, allowing these derivatives to simultaneously target hyperpigmentation and oxidative damage.
[Conclusion] This study demonstrates that alkyl esterification of PCA significantly enhances its anti-melanogenic and cytoprotective activities without inducing cytotoxicity. Consequently, these novel PCA alkyl esters hold great promise as safe and effective multi-functional ingredients for cosmeceutical applications aimed at skin whitening and anti-aging.
References
1. Cho J et al., Curr. Issues Mol. Biol. 45, 2157–2169 (2023).
2. Kang DY et al., Mol. Cell. Toxicol. (2025). https://doi.org/10.1007/s13273-025-00564-9
[Method] A series of PAE derivatives with varying alkyl chain lengths were synthesized via Steglich esterification using dicyclohexylcarbodiimide and 4-dimethylaminopyridine. The chemical structures were confirmed using H-NMR spectroscopy. To assess skin-whitening potential, B16F10 cells were stimulated with α-melanocyte-stimulating hormone (α-MSH), and the inhibitory effects on melanin content and cellular tyrosinase activity were measured. Western blot analysis was performed to examine the expression of key melanogenic proteins, including microphthalmia-associated transcription factor (MITF), tyrosinase, TRP-1, and TRP-2. Antioxidant capacities were evaluated using DPPH and ABTS radical scavenging assays, and cytoprotective effects against oxidative stress were assessed in HS68 fibroblasts.
[Results] The PAE derivatives were successfully synthesized with confirmed structures. In biological assays, the derivatives exhibited low cytotoxicity in both B16F10 and HS68 cell lines. Regarding whitening activity, PAEs significantly inhibited α-MSH-induced melanin accumulation and tyrosinase activity in a dose-dependent manner, demonstrating superior efficacy compared to the parent PCA. Western blotting revealed that PAEs effectively downregulated the protein expression of MITF, Tyrosinase, TRP-1, and TRP-2. Additionally, in antioxidant assays, the derivatives retained potent radical scavenging activities comparable to L-ascorbic acid and successfully protected HS68 fibroblasts from oxidative stress-induced cell death.
[Consideration] The superior biological activity of PAEs compared to PCA is likely attributed to the increased lipophilicity conferred by the alkyl ester chains, which facilitates enhanced cellular membrane permeability. The significant downregulation of MITF and downstream melanogenic enzymes suggests that the depigmenting mechanism of PAEs involves the modulation of the cAMP/PKA/CREB signaling pathway. Importantly, the structural modification at the carboxyl group did not compromise the antioxidant capacity derived from the catechol moiety, allowing these derivatives to simultaneously target hyperpigmentation and oxidative damage.
[Conclusion] This study demonstrates that alkyl esterification of PCA significantly enhances its anti-melanogenic and cytoprotective activities without inducing cytotoxicity. Consequently, these novel PCA alkyl esters hold great promise as safe and effective multi-functional ingredients for cosmeceutical applications aimed at skin whitening and anti-aging.
References
1. Cho J et al., Curr. Issues Mol. Biol. 45, 2157–2169 (2023).
2. Kang DY et al., Mol. Cell. Toxicol. (2025). https://doi.org/10.1007/s13273-025-00564-9
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