Molecular Action Mechanism of Coixol from Soft-Shelled Adlay on Tyrosinase: The Future of Cosmetics

Coix lacryma-jobi var. ma-yuen L. Gramineae is widely cultivated in Taiwan. Literature regarding the molecular action mechanism of coixol on tyrosinase and the application of coicis seed extracts to the processing of facial masks is still lacking. Solvent extractability analysis revealed that most of the polyphenolics in coicis seeds were water soluble (3.17 ± 0.12 to 3.63 ± 0.07 μg/mLGAE). In contrast, the methanolic extract contained the most flavonoids (0.06 ± 0.00~0.26 ± 0.03 μg/mL QE) and coixol (11.43 ± 0.13~12.83 ± 0.14 μg/mL), showing potent antioxidant capability. Additionally, the contents of coixenolide (176.77 ± 5.91 to 238.60 ± 0.21 μg/g), phytosterol (52.45 ± 2.05 to 58.23 ± 1.14 mg/g), and polysaccharides (3.42 ± 0.10 to 4.41 ± 0.10 mg/g) were rather high. The aqueous extract (10 μg/mL) and the ethanolic extract (1 mg/mL) showed no cytotoxicity to B16F10 melanocytes. More attractively, the ethanolic extract at 1 mg/mL caused 48.4% inhibition of tyrosinase activity in B16F10 melanocytes, and 50.7% on human tyrosinase (hTyr) fragment 369–377. Conclusively, the coicis seed extracts containing abundant nutraceuticals with promising anti-hTyr activity and moisturizing capability can serve as good ingredients for facial mask processing.