Nematicidal <i>Stemona</i> Alkaloids from <i>Stemona parviflora</i>

Abstract

Eight new alkaloids, 3β-n-butylstemonamine (1), 8-oxo-3β-n-butylstemonamine (2), 3-n-butylneostemonine (3), 10-epi-3-n-butylneostemonine (4), 8-oxo-oxymaistemonine (5) protostemonine N₄-oxide (6), (19S)-hydroxy-21-methoxystemofoline (7), and parvistemonine A (8), were isolated from the roots of Stemona parviflora, together with 17 known alkaloids. The structures of the new alkaloids were elucidated based on a comprehensive spectroscopic data analysis. The absolute configurations of 1-4 were determined by the ECD exciton chirality method and quantum ECD calculations. Protostemonine (10) and stemofoline (12) showed strong nematicidal activity against Panagrellus redivevus, with IC₅₀ values of 0.10 and 0.46 μM, respectively.