Antioxidant and anti-melanogenic activities of ultrasonic extract from Stichopus japonicus

Objective: To investigate the antioxidant and anti-melanogenesis activities of an ultrasonic extract of red sea cucumber, Stichopus japonicus, collected from Jeju Island.Methods: Antioxidant activity experiments were assessed by an electron spin resonance system and a cellular model of immortalized human keratinocytes (HaCaT) to determine its radical scavenging activity and protective effects against 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced oxidative stress. Anti-melanogenic activity of the ultrasonic extract of red sea cucumber was also examined using the melanoma cell model B16F10 and mushroom tyrosinase. Following the induction by alpha-melanocyte-stimulating hormone, the effects of the ultrasonic extract of red sea cucumber on intracellular tyrosinase activity, melanin content and the melanogenic protein expression of microphthalmia-associated transcription factor, tyrosinase, and tyrosinase-related proteins (TRP-1, and TRP-2) were examined.Results: The ultrasonic extract of red sea cucumber significantly scavenged 2,2-diphenyl-1-picrylhydrazyl and alkyl radicals [IC50: (0.924 +/- 0.035) and (0.327 +/- 0.006) mg/mL, respectively], as well as showed a protective effect against oxidative stress and attenuated generation of intracellular reactive oxygen species on AAPH- induced HaCaT cells, with no cytotoxicity (12.5-400 mu g/mL). The ultrasonic extract of red sea cucumber also exhibited a tyrosinase inhibitory effect [IC50: (2.750 +/- 0.006) mg/mL]. On alpha-melanocyte-stimulating hormone-stimulated B16F10 melanoma cells, the ultrasonic extract of red sea cucumber (25-200 mu g/mL) significantly inhibited not only melanin synthesis and tyrosinase activity, but also protein expressions of microphthalmia-associated transcriptional factor, tyrosinase, TRP-1, and TRP-2.Conclusions: The ultrasonic extract of red sea cucumber shows antioxidant and anti-melanogenic potential and may be a natural candidate for anti-aging as well as a whitening agent in the cosmeceuticals industry.