Obovatollignols A-E, five racemic forms of obovatol-derived dimeric neolignans from Magnolia officinalis var. biloba.

Five racemic forms of obovatol-derived dimeric neolignans, named obovatollignols A-E (1-5), were isolated from the cortexes of Magnolia officinalis var. biloba. Among them, obovatollignol A (1) represents a novel class of polycyclic neolignans featuring an unprecedented 2-oxahexacyclo [16.2.2.01,16.09,20.010,15.03,8]docosane skeleton, while obovatollignol B (2) was identified as its biosynthetic congener. Additionally, compounds 3-5 were identified as three undescribed obovatol dimers. The planar structures and absolute configurations of the compounds were established by a combination of HRESIMS, NMR spectroscopic data (1H, 13C, HSQC, HMBC, 1H-1H COSY, and ROESY), and single-crystal X-ray crystallography analysis, in conjunction with electronic circular dichroism (ECD) calculations. Evaluation of the isolated compounds for anti-inflammatory effects revealed that (±)-2, (+)-5, and (-)-5 significantly inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW264.7 macrophages, exhibiting IC50 values of 3.12 ± 0.05, 2.31 ± 0.26, and 1.86 ± 0.60 μM, respectively.