Exploring the Potential Effect and Mechanisms of Protocatechuic Acid on Human Hair Follicle Melanocytes

This study evaluated the effects of protocatechuic acid (PCA) on human hair follicle melanocytes (HFM). PCA treatments (0.1–200 μmol L−1) were found to decrease melanin synthesis and tyrosinase activity with IC50 values of 8.9 μmol L−1 and 6.4 μmol L−1, respectively, after 24 hours, without causing cytotoxicity. Additionally, PCA significantly reduced the mRNA transcription and protein expression levels of melanogenic genes (TRP-1, TRP-2, MITF) and increased the activity of antioxidant enzymes (SOD and GSH) in a dose-dependent manner. These findings suggested that PCA could inhibit melanin production through down-regulation of melanogenesis-related proteins and enhance antioxidant effects, potentially useful for treating melanin overproduction or for skin whitening.