Antioxidant Lignans and Neolignans from Acorus tatarinowii

Eleven new lignans and neolignans, named acortatarinowins G-N (1-8), including three pairs of enantiomers (1a/1b-3a/3b) and five optically pure lignans and neolignans (4-8), along with five known analogs (9-14), were isolated from the rhizomes of Acorus tatarinowii Schott. Compounds 1-3 were successfully separated by chiral HPLC to afford 1a/1b-3a/3b. The planar structures of 1-8 were elucidated by extensive spectroscopic analyses including HRESIMS and NMR. Their absolute configurations were determined by analyses of single-crystal X-ray diffraction and a modified Mosher's method, assisted by experimental and calculated electronic circular dichroism (ECD) data. Compounds 1a and 1b were rare 7,8'-epoxy-8,7'-oxyneolignane. Compounds 1-8 were evaluated for their antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl (DPPH) reducing antioxidant power assay. Compound 6, exhibiting strong DPPH radical scavenging capacity with IC50 value of 16.4 ± 0.22 μg/mL, could interpret the herbal traditional usage.