(P)/(M)-corinepalensin A, a pair of axially chiral prenylated bicoumarin enantiomers with a rare C-5C-5' linkage from the twigs of Coriaria nepalensis

A pair of undescribed bicoumarin enantiomers, (P)/(M)-corinepalensin A, two undescribed prenylated coumarins, corinepalensins B and C, along with ten known coumarins were isolated from the twigs of Coriaria nepalensis. (P)/(M)-corinepalensin A feature a rare C-5C-5' axially chiral linkage between two prenylated coumarin monomers. Their structures were determined by a combination of spectroscopic methods, single crystal X-ray diffraction, and ECD calculations. All isolates were evaluated for the inhibitory activity against phosphodiesterase-4 (PDE4), which is a drug target for the treatment of asthma and chronic obstructive pulmonary disease. Compounds (P)-corinepalensin A, (M)-corinepalensin A, corinepalensin B, norbraylin, braylin, and nepalin C exhibited significant inhibition with IC50 values ranging from 0.43 to 7.15 μM.