Four new bisindole alkaloids, melodinines H-K (1-4), a new monomer, melodinine L (5), and 11 known alkaloids were isolated from Melodinus tenuicaudatus. The structures of 1-5 were elucidated by extensive spectroscopic methods, and the known compounds were identified by comparison with data in the literature. All of the compounds were evaluated for their cytotoxicity against five human cancer cell lines. Alkaloids 1, 3, and 4 and the known compound 11-methoxytabersonine (8) exhibited inhibitory effects, with IC(50) values comparable to those of cisplatin and vinorelbine.
An unusual oxindole alkaloid inner salt, macrophyllionium (1), and a pair of new tetracyclic oxindole alkaloids, macrophyllines A (2) and B (3), together with six known alkaloids, were isolated from the aerial parts of Uncaria macrophylla. Corynantheidine (8) exhibited moderate cytotoxicity against HL-60 and SW480 cells with IC(50) values of 13.96 and 23.28 μM, respectively. Dihydrocorynantheine (9) exhibited significant vasodilating activity against phenylephrine-induced contraction in rat thoracic aorta rings (IC(50) = 6.73 μg/mL). In addition, compounds 2, 6, and 9 showed weak inhibitory action on KCl-induced contraction.
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