Novel lignans from Syringa pinnatifolia and protective effect against H 2 O 2 -induced oxidative injury through regulating the expression of Nrf2/HO-1 in H9c2 cells.

Phytochemical analysis of the peeled stems of Syringa pinnatifolia Hemsl. led to the discovery of 13 undescribed lignans, namely helanols A and B (1 and 2) and alashanenols W-G ₁ (3-13), as well as four known analogues, of which helanols A and B were lignans with novel skeleton of α-β' linkage. The structures were unambiguously established by extensive spectroscopic analyses, NMR calculations, ECD calculations, and single crystal X-ray crystallography. Five lignans (1, 2, 5, 11 and 13) exhibited a moderate protective effect against H ₂ O ₂ -induced oxidative injuries in H9c2 cells with the protective rates of 11.3-20.6 % at the concentration of 0.3-20 μM, while the positive control quercetin showed protective rates of 58.7 % at 10 μM. Further mechanism investigation suggested that 1 and 2 exerted the protective effect by regulating the expression of Nrf2/HO-1.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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