Biphenyl-type neolignans with NO inhibitory activity from the fruits of Magnolia tripetala

Tripetalins A (1) and B (2), two new biphenyl-type neolignans were obtained from the fruits of Magnolia tripetala, along with four known analogues. The structures of the new compounds were characterized by comprehensive spectroscopic analyses including 1H, 13C, and 2D NMR, IR, and HRESIMS data. Tripetalin A (1) was the first magnolol-honokiol-type neolignan dimer linked through C-5′‒C5′′ carbon bond. Magnoquinone (5) and magnotriol B (6) displayed remarkable NO inhibitory activity with IC50 values of 4.52 ± 0.07 and 2.02 ± 0.03 μM, respectively.