Extracts of red seaweed, Pyropia yezoensis, inhibit melanogenesis but stimulate collagen synthesis

Owing to increasing concern regarding human well-being and quality of life, the demand for natural products is increased, leading to the development of a market for biological and natural products. This study aimed to investigate the depigmentation and anti-ageing properties of red seaweed (Pyropia yezoensis) extracts for skin care applications. Within the tested range of concentrations (100, 200, 400, and 800 μg mL−1), P. yezoensis extracts did not exert cytotoxic effects on the three skin cell lines tested: mouse melanocytes (Melan-A), human dermal fibroblasts (1064 SK), and human dermal keratinocytes (HaCaT cells). No significant statistical difference (p = 0.05) was detected in the melanin content between cells exposed to 100 μg mL−1 of arbutin and 800 μg mL−1 of P. yezoensis extracts, indicating that P. yezoensis extracts had an potent inhibitory effect on melanogenesis as arbutin. There was a significant decrease in tyrosinase activity by 59.3% and 35.5% after treatment with arbutin and P. yezoensis extracts, respectively. These results indicated that P. yezoensis extracts had strong tyrosinase inhibitory properties but were not as effective as arbutin. P. yezoensis extracts also promoted collagen production by inhibiting collagen-degrading enzymes (matrix metalloproteinase (MMP)-2 and MMP-9) and promoting procollagen synthesis enzymes (tyrosinase-related protein (TRP)-1 and TRP-2). Evaluation of skin brightness and melanin content and dermatological assessment showed that P. yezoensis extracts enhanced skin brightness and reduced melanin content in 23 volunteers. Our results suggest that P. yezoensis extracts can be used as functional cosmetic agents to prevent, or remediate skin ageing and pigmentation.