Melanin Synthesis Inhibition and Radical Scavenging Activities of Compounds Isolated from the Aerial Part of Lespedeza cyrtobotrya

The EtOAc fraction of Lespedeza cyrtobotrya showed mushroom tyrosinase inhibitory and radical scavenging activities. Four active compounds were isolated based on Sephadex LH-20 chromatography and HPLC, and the structures were elucidated, on the basis of their LC-MS and NMR spectral data, as 2-(2,4-dihydroxyphenyl)-6-hydroxybenzofuran (1), eriodictyol-7-O-glucopyranoside (2), haginin A (3), and dalbergioidin (4), respectively. Compound (1) showed mushroom tyrosinase inhibitory activity with an IC∧50 value of 5.2 μM and acted as a competitive inhibitor. Furthermore, 37.3 μM of compound 1 reduced 50% of the melanin content on human melanoma (MNT-1) cells. The radical scavenging activities of compounds 1, 2, 3, and 4 were shown to have IC∧50 values of 11.0, 24.5, 9.0, and 36.5 μM, respectively, in an ABTS system and 1C∧50 values of 42.7, 36.0, 37.7, and 61.71 μM, respectively, in a DPPH system. The mushroom tyrosinase inhibitory activity of the EtOAc fraction of Lespedeza cyrtobotrya was contributed by compounds 1, 3, and 4, and its radical scavenging activity was contributed by compounds 1-4.