Alstobrogaline, an unusual pentacyclic monoterpenoid indole alkaloid with aldimine and aldimine-N-oxide moieties from Alstonia scholaris

Alstobrogaline ( 1 ), an unusual monoterpenoid indole alkaloid incorporating a third N atom and possessing two aldimine functions, with one being in the form of N -oxide, was isolated from the leaves of Alstonia scholaris . Its structure and relative configuration were determined by extensive NMR spectroscopic analysis, while its absolute configuration was established by X-ray diffraction analysis. A possible biogenetic pathway to 1 was proposed. Compound 1 displayed weak cytotoxic effects against MDA-MB-231 and MCF7 breast cancer cells.