Two new N-oxide alkaloids from Stemona cochinchinensis

Two new N-oxide alkaloids with pyrrolo[1,2-α]azepine skeleton, namely isoneostemocochinine-N-oxide (1) and neostemocochinine-N-oxide (2), as well as three known alkaloids with pyrido[1,2-α]azepine skeletons, were isolated and identified from the roots of Stemona cochinchinensis (Stemonaceae). The structures of these compounds were elucidated by 1D- and 2D-NMR spectra and other spectroscopic studies. Additionally, the 1H- and 13C-NMR characteristic of N-oxide Stemona alkaloids was summarized. Stemokerrin showed potent anti-tussive activity on citric acid-induced guinea pig model.