Antiplatelet activities of aporphine alkaloids isolated from leaves of Magnolia obovata.

Five aporphine alkaloids, N-acetylanonaine ( 1), N-acetylxylopine ( 2), N-formylanonaine ( 3), liriodenine ( 4), and lanuginosine ( 5) as the antiplatelet constituents, were isolated from the methanol extract of leaves of Magnolia obovata. This is the first reported occurrence of 2 and 3 from genus Magnolia and 5 was isolated from this plant for the first time. Compounds 1, 2 and 3 showed 60 approximately 264-fold stronger inhibitory effects than acetylsalicylic acid (ASA) to rat platelet aggregation induced by collagen, epinephrine, arachidonic acid (AA), or U46619.