Hyper-activated melanocytes are known to be the primary cause of skin hyper-pigmentary disorders, such as freckles and melasma. The researchers found that most of the plant-derived skin-whitening agents suppressed melanin production by modulating the expression of melanogenesis-related proteins, such as MITF, Tyrosinase, TRP-1, and TRP-1, while a few plant-derived skin-whitening agents promoted ERK signaling pathways, resulting in accelerated MITF degradation and regulating the length of melanocyte dendrites, which supposedly block melanin transportation. 

Ocean-derived agents primarily demonstrated suppression in melanin production by inhibiting the enzymatic activity of Tyrosinase, either competitively or noncompetitively whereas Bacteria-derived skin-whitening agents suppressed melanin production by regulating Tyrosinase activity and melanogenic proteins. Surprisingly, the fermented extracts demonstrated higher inhibitory activity than non-fermented extracts, which may be partly due to the combined effects of plant- and bacteria-derived active ingredients. 

The skin lightening efficiency of arbutin alone or in combination with other active ingredients has been clinically evaluated. Arbutin impedes the catalytic activity of TYR or causes its irreversible inactivation, thereby preventing the synthesis of melanin in cells. Arbutin is used as an effective treatment of hyperpigmentary disorders and displays less melanocyte cytotoxicity.

Source: Int J Mol Sci. 2021;22(12):6206. Published 2021 Jun 8. doi:10.3390/ijms22126206. International Journal of Cosmetic Science, 33, 210–221 211