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, (2S)-4’-hydroxy-6,7-dimethoxyflavan (1), (2S)-3’,4’-dihydroxy-7-methoxy-8-methylflavan (2), (2S)-2’-hydroxy-7-methoxyflavan (3), and (2S,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 IC50 values of 8.6 and 14.5 μM, respectively.