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Quaternary alkaloids in Magnoliae Cortex were isolated by the ion-pair extraction-preparative ion-pair HPLC method, in which sodium perchlorate was utilized as the ion-pair reagent. Quaternary alkaloids form ion-pairs with perchlorate anion and the resulting ion-pairs are extractable with 1,2-dichloroethane under acidic conditions. The quaternary alkaloids thus obtained were efficiently separated by ion-pair HPLC in which sodium perchlorate was also utilized. When preparative HPLC was used, the effluent was concentrated to remove the organic solvent such as acetonitrile, and by extracting the residue with 1,2-dichloroethane and evaporating 1,2-dichloroethane, quaternary alkaloids were obtained as perchlorate of pure alkaloids. Seven quaternary bases were thus isolated from Magnoliae Cortex and their structures were elucidated. Of them, (+)-laurifoline, (±)-oblongine, (+)-menisperine, (+)-xanthoplanine and (+)-N-methylglaucine were isolated for the first time from Magnolia obovata.