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 IC(50) value of 16.4 ± 0.22 μg/mL, could interpret the herbal traditional usage.