Antioxidant lignans and chromone glycosides from Eurya japonica

Four new 8,8',7,2'-lignans, (+)-ovafolinin B-9'-O-β-d-glucopyranoside (1), (-)-ovafolinin B-9'-O-β-d-glucopyranoside (2), (+)-ovafolinin E-9'-O-β-d-glucopyranoside (3), and (-)-ovafolinin E-9'-O-β-d-glucopyranoside (4), two neolignans, eusiderin N (5) and (7S,8R)-3,5,5'-trimethoxy-4',7-epoxy-8,3'-neolignan-9,9'-diol-4-O-β-d-xylopyranoside (6), and two new chromone glycosides, 5,7-dihydroxy-4H-chromen-4-one-3-O-β-d-glucopyranoside (7) and 5,7-dihydroxy-4H-chromen-4-one-3-O-β-d-xylopyranoside (8), together with 25 known compounds, were isolated from the stems of Eurya japonica. Structural elucidation of compounds 1-8 was established by spectroscopic methods, especially 2D NMR techniques, electronic circular dichroism data, and comparison with reported data. The isolates were evaluated for antioxidant and anti-NO production activities. Compounds 1, 2, 12-20, and 29 (ED50 23.40 μM for 1) demonstrated potent antioxidant activity compared to the positive control α-tocopherol (ED50 27.21 μM). On the other hand, compounds 1, 2, 7-9, 12-20, and 32 showed only weak anti-NO production activity when compared to the positive control quercetin.