Eleven new indole alkaloids, alstoniascholarines AeK (1e11), along with one known analogue, were
isolated from the aqueous fraction of Alstonia scholaris leaf extract. Their structures were established on
the basis of extensive spectroscopic data analysis, chemical transformation, and quantum theory. Alkaloid
4 possessed a novel skeleton with fused-ring and a six-membered ring, the absolute configuration of
which was assigned by quantum theory. Alkaloids 6 and 10 showed the best antibacterial activity against
Pseudomonas aeruginosa with an MIC value of 3.13 mg/mL.