Skin-whitening effect of Haematococcus pluvialis extract and its synergy with niacinamide

Dysregulation of melanin metabolism is a primary cause of skin hyperpigmentation, making the regulation of melanin synthesis and transfer a key focus in skin-whitening research. Haematococcus pluvialis extract (HPE), a potent natural antioxidant, is widely used in cosmetics. Thus, HPE is a potential candidate for the development of skin-whitening agents. This study aims to investigate the effects of HPE on melanin synthesis and melanosome transfer, and the synergistic interactions with niacinamide (NAM). α-melanocyte-stimulating hormone (α-MSH)-induced mouse melanoma cells (B16F10) were used to evaluate the effects of HPE and NAM on tyrosinase activity and melanin synthesis. A transwell coculture system of human keratinocyte cells (HaCaT) and human melanoma cells (MNT-1) was established to further investigate the impact of HPE, NAM, and their combination on melanin synthesis and melanosome transfer. The combination index (CI) was calculated using the Bliss Independence model. In B16F10 cells, HPE significantly inhibited tyrosinase activity and melanin synthesis, with inhibition rates of 22% and 34%, respectively ( p < 0.05). The transwell coculture system further demonstrated that HPE markedly reduced both melanin content and the number of melanosomes in HaCaT cells ( p < 0.05). Additionally, the combination of HPE and NAM demonstrated the synergistic effect on melanin transfer ( CI < 1). This study demonstrates that HPE’s skin-whitening effect is achieved by inhibiting tyrosinase activity and melanosome transfer, thereby reducing melanin production. These findings provide a more comprehensive understanding of HPE's mode of action. Furthermore, the synergistic enhancement between HPE and NAM paves the way for novel skin-whitening product formulations.