A new lignan from the roots of Syringa pinnatifolia.

Phytochemical investigation of the roots of Syringa pinnatifolia has resulted in the isolation of a new lignan, pinnatifolin A (1), together with seven known compounds (2-8). The structures were elucidated on the basis of extensive spectroscopic methods, including NMR, MS, UV and IR spectra. The seven lignans were screened for their antioxidant activity (DPPH assay), and most of them showed potent antioxidant activity.