Isolation and structural elucidation of bioactive obovatol dimeric neolignans from the bark of Magnolia officinalis var. biloba

(+)/(-)-Diobolignans A-F, six pairs of enantiomeric obovatol dimeric neolignans, were isolated from the bark of Magnolia officinalis var. biloba. (+)/(-)-Diobolignans A to C possessed a dioxane ring between the benzene ring and the propyl side chain, while (+)/(-)-diobolignans D to F possessed a furan ring. Meanwhile, (+)/(-)-diobolignans B and C, as well as (+)/(-)-diobolignans E and F, were two epimeric pairs of enantiomers, respectively. Their structures were determined by extensive analyses of HRESIMS, UV, IR, NMR and electronic circular dichroism (ECD) calculations. The bioassay showed (+)-diobolignan A displayed cytotoxic activities against human cancer cell lines HGC27 and HT29 with the IC50 values of 9.43 and 9.45 mu M, respectively. In addition, (-)-diobolignan A and (+/-)-diobolignan E showed neuroprotective effect on glutamic acid-induced cellular damage in SK-N-SH cell.

Automated summary

Six pairs of enantiomeric obovatol dimeric neolignans were isolated from the bark of Magnolia officinalis var. biloba, with one enantiomer showing cytotoxic activity against human cancer cell lines and two others exhibiting neuroprotective effects on glutamic acid-induced cellular damage.