Background: Annona muricata (A. muricata) L. (also known as graviola) contains various antioxidants that have beneficial effects on headaches, hypertension, coughs and asthma. A. muricata L. also has various other physiological effects, such as antispasmodic effects for the treatment of heart conditions, and sedative and nervine effects. In the present study, the effect of A. muricata L. extracts on melanogenesis was investigated and the ensuing inhibitory mechanisms were determined. Methods: The inhibitory effects of A. muricata L. extracts on melanogenesis were initially investigated by measuring melanin contents. Subsequently, the ensuing mechanisms were characterized by determining changes in the activity of tyrosinase, which is the rate-limiting step of melanogenesis. Finally, mRNA and protein expression levels of tyrosinase and the melanogenesis-associated transcription factor (MITF) were determined. Results: Decreased melanin contents after treatments with A. muricata L. extracts suggested skin-whitening effects, and these changes were reflected by decreased tyrosinase activities. In addition, tyrosinase mRNA and protein expression levels were regulated by A. muricata L. extracts. MITF is a known key transcription factor of tyrosinase and was transcriptionally regulated by A. muricata L. extracts. Specifically, MITF mRNA expression levels were decreased in the presence of A. muricata L. extracts. Taken together, the melanogenesis-moderating effects of A. muricata L. extracts follow suppression of MITF mRNA expression and subsequent transactivation of tyrosinase. Conclusions: The results of the present study confirm the skin-whitening effects of A. muricata L. and characterize the related molecular mechanisms. These data indicate that A. muricata L. has high potential as an ingredient of skin-whitening cosmetics.
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