Tyrosinase Inhibitors Derived from Chemical Constituents of Dianella ensifolia .

Dianella   ensifolia is a perennial herb with thickened rhizome and is widely distributed in tropical and subtropical regions of Asia, Australia, and the Pacific islands. This plant has the potential to be used as a source of herbal medicine. This study investigated further phytochemistry and tyrosinase inhibitory effect of some constituents isolated from D. ensifolia . Four new flavans, (2 S )-4'-hydroxy-6,7-dimethoxyflavan ( 1 ), (2 S )-3',4'-dihydroxy-7-methoxy-8-methylflavan ( 2 ), (2 S )-2'-hydroxy-7-methoxyflavan ( 3 ), and (2 S ,1' S )-4-hydroxy-4-(7-methoxy-8-methylchroman-2-yl)-cyclohex-2-enone ( 4 ), together with 67 known compounds, including 10 flavans ( 5 - 14 ), 5 flavanones ( 15 - 19 ), 3 flavone ( 20 - 22 ), 5 chalcones ( 23 - 27 ), 3 chromones ( 28 - 30 ), 15 aromatics ( 31 - 45 ), 7 phenylpropanoids ( 46 - 52 ), one lignan ( 53 ), 7 steroids ( 54 - 60 ), one monoterpene ( 61 ), one diterpene ( 62 ), 4 triterpenes ( 63 - 66 ), a carotenoid ( 67 ), 2 alkaloids ( 68 and 69 ), and 2 fatty acids ( 70 and 71 ) were isolated from D. ensifolia . Their structures were elucidated on the basis of physical and spectroscopic data analyses. Moreover, compounds 1 - 4 , 8, 10 - 15, 20, 21, and 41 were evaluated for their mushroom tyrosinase inhibitory effect. Compounds 11 and 14 strongly inhibited mushroom tyrosinase activity with IC 50 values of 8.6 and 14.5 μM, respectively.