2013 Volume 13 Issue 1 Pages 14-20
In this study, we examined the characteristics of yuzu seed oil and investigated its potential as a carrier for aromatherapeutic applications. Yuzu and sweet almond oil were sampled and the potency of the released aroma volatiles was measured. The potency of each oil was represented as the cumulative quantity of major volatile components, including lavender (Lavandula officinalis), sweet orange (Citrus sinensis), eucalyptus (Eucalyptus globulus), and yuzu (Citrus junos). The aroma-releasing potency of volatile components from yuzu seed oil was significantly higher compared with that of sweet almond oil. In the oil treatment test, one forearm (either right or left) of each of the 20 subjects was treated with 0.5 mL of sample oil every night for 4 weeks. Transepidermal water loss, water content of stratum corneum, melanin concentration, hemoglobin level, skin color, and skin texture were measured just before initiation of the treatment, the next day after initiation of treatment, and 1 and 2 weeks after the treatment period of 28 days. The water content of stratum corneum was high after the treatment and decreased thereafter. This suggests that moisture retention increased transiently during the treatment with carrier oils. Both oils caused a significant decrease in skin melanin concentration, and this effect persisted for at least 2 weeks after completion of the treatment. Because melanin is associated with skin lightening, the effect of the oils on the activity of tyrosinase, which is involved in melanin biosynthesis, was verified. Both oils inhibited mushroom tyrosinase, and inhibition by yuzu seed oil was significantly greater compared with that by sweet almond oil. We also developed a new analytical method for determining tyrosinase activity, which is applicable to non-polar oil samples. In conclusion, we demonstrated that yuzu seed oil is suitable as carrier oil for aromatherapeutic applications. Moreover, this is the first report to demonstrate the skin-lightening effects of both yuzu and sweet almond oil.
