Chiral separation and bioactivities of six pairs of enantiomeric dilignans from Magnolia officinalis var. biloba

Abstract

Six pairs of enantiomeric dilignans, (+)/(−)-magdiligols A–F, have been isolated from an ethanolic extract of the barks of Magnolia officinalis var. biloba. Their chemical structures were elucidated by extensive spectroscopic analyses, NMR calculation with DP4+ analysis, and the electronic circular dichroism spectra calculation. (+)/(−)-1–3 possessed a dihydrobenzopyran ring, while a propyl chain of 1 was linked via ether bond. (+)/(−)-Magdiligols D and E ((+)/(−)-4 and 5) were dilignans possessing a furan ring. (+)-Magdiligol B ((+)/(−)-2), (+)/(−)-magdiligol C ((+)/(−)-3), and racemes 2, 3, and 5 showed potential hepatoprotective effects against APAP-induced HepG2 cell damage, increased the cell viability from 65.4% to 72.7, 78.7.76.6, 73.9, 77.9 and 73.2%, via decreasing the level of the live enzymes ALH and LDH consistently. (+)/(−)-Magdiligols B–D ((+)/(−)-2–4) and (+)/(−)-magdiligol F ((+)/(−)-6) exhibited significant antioxidative activity. (+)/(−)-Magdiligols B–C ((+)/(−)-2 and 3), (−)-magdiligol D ((−)-4), and (+)-magdiligol E ((+)-5) displayed significant PTP1B inhibitory activity with IC50 values 1.41–3.42 μM. (+)/(−)-Magdiligol B ((+)/(−)-2), and its raceme (2) demonstrated α-glucosidase inhibitory activity with the IC50 values 1.47, 2.88 and 1.85 μM, respectively.