Phytochemical constituents of Coix lachryma-jobi var. ma-yuen roots and their tyrosinase inhibitory activity
2017
Choi, Y.H., Gyeonggido Business and Science Accelerator, Suwon, Republic of Korea | Choi, C.W., Gyeonggido Business and Science Accelerator, Suwon, Republic of Korea | Lee, J.Y., Gyeonggido Business and Science Accelerator, Suwon, Republic of Korea | Ahn, E.K., Gyeonggido Business and Science Accelerator, Suwon, Republic of Korea | Oh, J.S., Dankook University, Cheonan, Republic of Korea | Hong, S.S., Gyeonggido Business and Science Accelerator, Suwon, Republic of Korea
In the course of screening tyrosinase inhibitory activity, EtOAc-soluble fraction of Coix lachryma-jobi var. mayuen Stapf. (Gramineae) roots showed significant inhibition. Further fractionation of the EtOAc-soluble fraction resulted in six compounds, which were identified as (+)-icariol A2 (1), zhepiresionol (2), 4-hydroxybenzaldehyde (3), trans-ρ-coumaric acid (4), N-(2- hydroxy-4-methoxyphenyl)-2-hydroxyacetamide (5), and coixol (6). The chemical structures of these compounds were identified on the basis of spectroscopic methods (MS, 1D and 2D NMR) and comparison with literature values. Compound 1 was first reported from this plant. Also, this is the first time that the isolation of compound 5 has been reported from nature source. Among the isolated compounds, compounds 4 and 6 showed enzyme inhibitory activity, with IC50 values of 6.5 and 62.4 μM, respectively, in comparison with these of positive control, arbutin.
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