56 JOURNAL OF COSMETIC SCIENCE (A) (B) Figure 11. Morphology of melanocyte B 16Fl melanoma cells treated with (A) 0.1 % DMSO (control), (B) 10 µg/ml of A. incisus ether extract, and (C) 4.5 µg/ml of artocarpin for three days. Magnification: 400x.

BREADFRUIT EXTRACT AS SKIN LIGHTENER 57 (C) Figure 11. Continued With all findings taken together, we have found that A. incisus crude extract of diethyl ether at a concentration of 10 µg/ml exhibits non-cytotoxicity, potent tyrosinase inhibi­ tory activity, and the ability to reduce the melanin content in melanocyte cell culture. Previous studies revealed several kinds of phenolic compounds in the heartwood of A. incisus. Such phenolic compounds have been reported to have tyrosinase-inhibitory ac­ tivity and have been studied as depigmenting agents (1,21). Additionally, their anti­ oxidant property may prevent or delay pigmentation by different mechanisms, such as by scavenging ROS and reactive nitrogen species, or by reducing o-quinones or other intermediates in melanin biosynthesis. Therefore, the action of A. incisus ether extract on tyrosinase may be due, at least in part, to the phenolic components of the extract. Its antioxidant activity, together with its tyrosinase-inhibitory activity, would provide much more benefit. As compared to Marus alba (mulberry extract), the A. incisus ether extract seems to be a stronger tyrosinase inhibitor. IC 50 tyrosinase inhibition of mulberry extract was 78.3 µg/ml, and EC 50 DPPH radical scavenging activity was more than 100 µg/ml (22). Our findings indicate the potential of the A. incisus ether extract for appli­ cation in skin lightening. However, further studies, including those on toxicity to the human cell, irritability, and in vivo toxicity and efficacy, should be performed to estimate the value of the extract for marketing in the future. ACKNOWLEDGMENTS We thank Dr. Kuniyoshi Shimizu, Faculty of Agriculture, Kyushu University, Japan, for supplying purified artocarpin. We also thank the Faculty of Pharmaceutical Sciences, Naresuan University, for its research grant.