WHITENING AND ANTIAGING EFFECT OF SESAMOL 77 DISCUSSION Oxidative stress is induced by various factors leading to oxidation of biomolecules (e.g., lipids, proteins, and DNA) and pathological status (22). Under certain physiological conditions, when the level of ROS increases more than the intracellular antioxidant ca- pacity, oxidative stress will occur. The tyrosinase enzyme in melanogenesis also increases the oxidative risk in physiological systems (23). Therefore, antioxidant is benefi cial for antiaging. Our study demonstrates that sesamol can play an important role as an anti- oxidant because it possesses radical scavenging, lipid peroxidation prevention, and reduc- ing power. Our results confi rm the radical scavenging of sesamol as reported by Suja et al. (24) and Hayes et al. (25). Moreover, sesamol has the strongest lipid peroxidation preven- tion among our tested compounds. Occurring in cell membranes, lipid peroxidation re- leases arachidonic acid, which is involved in the infl ammatory response (26). Sesamol can hereby protect the cell membrane which is composed of a lipid bilayer from lipid peroxi- dation and might also prevent the infl ammatory process from decreasing arachidonic acid. Chen and Ahn (27) reported that sesamol inhibited lipid oxidation in UV-induced lipid oxidation in the following order: quercetin rutin = caffeic acid = ferulic acid = sesamol catechin. The advantage of a reducing ability is the capacity to neutralize free radicals and to stabilize and stop harmful chain reactions (17). In this study, sesamol pos- sessed the reducing ability according to the results of the FRAP assay. Melanogenesis is a natural mechanism—the product of melanocytes. Melanin is a pigment for preventing UV-induced skin damage and that acts as a photoprotectant (28). The abnor- mal accumulation of melanin leads to hyperpigmentation which is a main concern in cos- metics. Anti-tyrosinase agents are therefore important ingredients in cosmeceuticals for skin whitening. Skin aging can be classifi ed as intrinsic and photo albeit both processes induce skin wrinkling. UV radiation generates ROS that can induce a transcription factor that promotes collagen destruction by upregulating enzymes, matrix metalloproteinases (MMPs). These MMPs induce collagen destruction, resulting in wrinkle formation. Laxity and fragility of the skin are also caused by ROS-activated hyaluronidase and elastase, which block hyaluronan and elastin formation, respectively (29). Since ROS causes photo and in- trinsic aging, protection from UV radiation and antioxidant homeostasis is crucial. Based on the results of this study, sesamol can supplement antioxidants, which can inhibit ROS via multiple mechanisms, and it acts as photoprotection. So, sesamol can be successfully used against the skin wrinkling associated with photoaging. In this study, cellular toxicity was determined in the human melanoma cell line (SK- MEL2) and the normal (Vero) cell line by using the NR assay after treating them with various compounds for 48 h. The known whitening agents—kojic acid and β-arbutin— and sesamol had negligible cytotoxicity on the SK-MEL2 and Vero cell lines. It should be noted that the concentration of sesamol that can inhibit cellular tyrosinase was much lower than the cytotoxic concentration. This study demonstrated that sesamol inhibits tyrosinase activity against mushroom ty- rosinase and human melanoma tyrosinase in a dose-dependent manner. These data were found to be in agreement with the previous studies regarding mushroom tyrosinase inhi- bition of sesamol (30). Tyrosinase inhibition of sesamol at the fi rst and second step of melanin biosynthesis is reportedly due to competitive and non-competitive inhibition, respectively (31). β-Arbutin was previously reported to have no inhibition effect on mush- room tyrosinase but had an inhibition effect against melanoma tyrosinase (32). It has

JOURNAL OF COSMETIC SCIENCE 78 been suggested that the cellular tyrosinase inhibition of β-arbutin is due to the intracel- lular conversion of arbutin to hydroquinone via the hydrolysis reaction by bacteria on the skin of humans (33). It is evidenced that the glycosidic linkage of arbutin structure could be cleaved in the cellular assay resulting in the tyrosinase inhibitory activity (34). Moreover, previous study reported that α-arbutin, which is the other isomer form, was also found to be active based on cell-based assay (35). β-Arbutin was reported to possess lesser tyrosinase inhibitory effect than α-arbutin (35). Our study found that β-arbutin exhibited low tyrosinase inhibitory effect which is in agreement with this report. CONCLUSIONS Evidence clearly shows that sesamol possesses high antioxidant properties and anti- tyrosinase activity. Importantly, sesamol was less cytotoxic in the human melanoma cell line (SK-MEL2). This study illustrates that sesamol—a lignan from edible sesame— could be used for cosmeceutical purposes. The molecular mechanisms underlying the antimelanogenic effect in vitro and in vivo and the safety of sesamol in vivo need clarifi cation. ACKNOWLEDGMENTS MS is grateful to the Pibulsongkram Rajabhat University, Thailand, for a PhD scholar- ship and to Graduate school for the fi nancial support of dissertation project (54212107). In fi scal year 2011 (542800) and 2012 (552900), Khon Kaen University Research Fund- ing provided fi nancial support for this project. The authors thank Mr. Bryan Roderick Hamman and Mrs. Janice Loewen-Hamman for assistance with the English-language presentation of the manuscript. REFERENCES (1) S. H. Park, S. N. Ryu, Y. Bu, H. Kim, J. E. Simon, and K. S. Kim, Antioxidant components as potential neuroprotective agents in sesame (Sesamum indicum L.), Food Rev. Int., 26, 103–121 (2010). (2) J. Lee and E. Choe, Extraction of lignan compounds from roasted sesame oil and their effects on the autoxidation of methyl linoleate, J. Food Sci., 71, 430–436 (2006). (3) P. J. Kanu, J. Z. Bahsoon, J. B. Kanu, and J. B. Kandeh, Nutraceutical importance of sesame seed and oil: a review of the contribution of their lignans, Sierra Leone J. Biomed. Res., 2, 4–16 (2010). (4) A. S. Rao, K. S. Rashmi, A. K. Nayanatara, A. Kismat, D. Poojary, and S. R. Pai, Effect of antibacterial and antifungal activities of Sesamum indicum, WJPR, 2, 1676–1680 (2013). (5) S. Periasamy, D.-Z. Hsu, S.-Y. Chen, S.-S. Yang, V. R. M. Chandrasekaran, and M.-Y. Liu, Therapeutic sesamol attenuates monocrotaline-induced sinusoidal obstruction syndrome in rats by inhibiting matrix metalloproteinase-9, Cell Cell Biochem. Biophys., 61, 327–336 (2011). (6) P. Y. Chu, S. P. Chien, D. Z. Hsu, and M. Y. Liu, Protective effect of sesamol on the pulmonary infl am- matory response and lung injury in endotoxemic rats, Food Chem. Toxicol., 48, 1821–1826 (2010). (7) S. Ramachandran, N. Rajendra Prasad, and S. Karthikeyan, Sesamol inhibits UVB-induced ROS gen- eration and subsequent oxidative damage in cultured human skin dermal fi broblasts, Arch. Dermatol. Res., 302, 733–744 (2010). (8) S. Pillai, C. Oresajo, and J. Hayward, Ultraviolet radiation and skin aging: roles of reactive oxygen spe- cies, infl ammation and protease activation, and strategies for prevention of infl ammation-induced ma- trix degradation – a review, Int. J. Cosmet. Sci., 27, 17–34 (2005). (9) A. K. Gupta, M. D. Gover, K. Nouri, and S. Talyor, The treatment of melasma: A review of clinical trials, J. Am. Acad. Dermatol., 55, 1048–1065 (2006). (10) V. M. Sheth and A. G. Pandya, Melasma: a comprehensive update: part I, J. Am. Acad. Dermatol., 65, 689–697 (2011).