Antibacterial monoterpenoid indole alkaloids from Alstonia scholaris cultivated in temperate zone

Three new monoterpenoid indole alkaloids, named normavacurine-21-one (1), 5-hydroxy-19, 20-E-alschomine (2), and 5-hydroxy-19, 20-Z-alschomine (3), together with thirteen known indole alkaloids (4-16) were isolated from the leaves of Alstonia scholaris cultivated in Kunming. Their structures were elucidated on the basis of extensive spectroscopic analysis, as well as by comparison with the reported spectroscopic data. The leaves of A. scholaris cultivated in Kunming, contained picrinine-type alkaloids, scholaricin-type alkaloids and nareline as major alkaloids. New compounds 1-3 might be derived from a common biogenetic precursor (5). Compounds 1, 5 and 10 exhibited significant antibacterial activity against Enterococcus faecalis, and 3, 9 and 14 against Pseudomonas aeruginosa with an MIC value of 0.781 μg/mL, while 14 showed moderate activity against Klepsiella pneumonia with an MIC value of 1.56 μg/mL.