Revision of NMR assignment for Morin-3- O -glucoside and microbial production of Morin-2’- O -glucoside

Morin is a flavonol having 2’,4’-dihydroxy group on B-ring identified especially in Moraceae plants. While morin is widely known, its glycosides are relatively rare. To the best of our knowledge, morin-3- O -glucoside ( 1 ) was first reported in 2008. However, the reported chemical shift values of 1 were unsatisfactory with those of the aglycone, morin, which is rather similar to quercetin-3- O -glucoside ( 2 ). Therefore, we prepared morin-3- O -glucoside ( 1 ) by microbial transformation of morin with Cunninghamella sp., and the NMR assignment was reinvestigated. The microbial culture also produced another compound ( 3 ). The NMR and MS analyses of 3 revealed it as a novel compound, morin-2’- O -glucoside ( 3 ). In this study, the revision of the NMR assignment of morin-3- O -glucoside ( 1 ), and the preparation and structural elucidation of a novel compound, morin-2’- O -glucoside ( 3 ), were described. Graphical abstract