Safe and effective ingredients capable of removing undesired hyperpigmentation from\nfacial skin are urgently needed for both pharmaceutical and cosmetic purposes. Deoxyarbutin\n(4-[(tetrahydro-2H-pyran-2-yl) oxy] phenol, D-Arb) is a glucoside derivative of hydroquinone.\nHere, we investigated the toxicity and efficacy of D-Arb at the sub-cellular level\n(directly on melanosomes) and skin pigmentation using in vivo and in vitro models to compare\nwith its parent compound hydroquinone (1,4-benzenediol, HQ). At first, we examined\nthe ultrastructural changes of melanosomes in hyperpigmented guinea pig skin induced by\n308-nm monochromatic excimer lightand/or treated with HQ and D-Arb using transmission\nelectron microscopy. The results showed that prominent changes in the melanosomal\nmembrane, such as bulb-like structure and even complete rupture of the outer membranes,\nwere found in the skin after topical application of 5% HQ for 10 days. These changes were\nbarely observed in the skin treated with D-Arb. To further clarify whether membrane toxicity\nof HQ was a direct result of the compound treatment, we also examinedultrastructural\nchanges of individual melanosomes purified from MNT1 human melanoma cells. Similar\nobservations were obtained from the naked melanosome model in vitro. Finally, we determined\nthe effects of melanosomal fractions exposed to HQ or D-Arb on hydroxyl radical\ngeneration in the Fenton reaction utilizing an electron spin resonance assay. D-Arb-treated\nmelanosomesexhibit a moderate hydroxyl radical-scavenging activity, whereas HQ-treated\nmelanosomessignificantly generate more hydroxyl free radicals. This study suggests that\nD-Arb possesses a potent ability in skin lightening and antioxidation with less melanosome\ncytotoxicity.
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