Tsai_2010_J.Nat.Prod_73_1632

The active fraction of the EtOH extract of the stem of Annona glabra against acetylcholinesterase (AChE) was analyzed by combining HPLC microfractionation with a bioassay. The analytical-scale sample was fractionated by HPLC-DAD into 96-well microplates, which, after evaporation, were assayed against AChE. The active subfractions were scaled up by separation over semipreparative HPLC to give 20 compounds. Four of these, (7S,14S)-(-)-N-methyl-10-O-demethylxylopinine salt (3), S-(-)-7,8-didehydro-10-O-demethylxylopininium salt (10), S-(-)-7,8-didehydrocorydalminium salt (11), and 5-O-methylmarcanine D (17), were assigned as new natural products. In addition, compounds 10 and 11 represent the first natural occurrence of 7,8-didehydroprotoberberines. Compound 3, pseudocolumbamine (12), palmatine (15), and pseudopalmatine (16) showed anti-AChE IC50 values of 8.4, 5.0, 0.4, and 1.8 muM, respectively.