Fig. 2 in Alkaloid and iridoid glucosides from Palicourea luxurians (Rubiaceae: Palicoureeae) indicate tryptamine- and tryptophan-iridoid alkaloid formation apart the strictosidine pathway

Fig. 2. Structures of iridoids isolated from leaves and stem bark of Palicourea luxurians are asperuloside (6), secoxyloganin (7), demethylsecologanol (8), secologanic acid (9) and sweroside (10). Furthermore, the secologanin isolation artifacts (E)-aldosecologanin (11), secologanin dimethyl acetal (12), secologanin di-n-butyl acetal (13) as well as both diastereomeres of secologanin n-butyl methyl acetal (14a/14b) are shown. Compounds 6 and 7 have been isolated from the stem bark, all other compounds have been isolated from the leaves.