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Five novel bisindole alkaloids, hunzeylanines A-E (1-5), with an unprecedented skeleton were isolated from the roots of Hunteria zeylanica. Compounds 1-5 represent the first examples of akuammine-pleioarpamine-type bisindole alkaloids fused with a dihydropyran unit. Their structures including absolute configurations were established through comprehensive spectroscopic data analyses and computational calculation methods. The plausible biogenetic pathway of 1 was also proposed. Alkaloids 1 and 2 displayed moderate cytotoxicity toward three human cancer cell lines (MDA-MB-231, AV3, and Huh7).

Four new corynanthe-type alkaloids, meloslines C-F (1-4), together with four known ones (5-8) were isolated from the roots of Alstonia scholaris. Their structures including absolute configurations were elucidated by extensive spectroscopic analysis and electronic circular dichroism (ECD) calculation. Compounds 1 and 2 exhibited potent vasorelaxant activity on endothelium-intact renal arteries precontracted with KCl.

Three new monoterpenoid indole alkaloids, alstratines A–C (1–3), along with three known ones were isolated from Alstonia rostrata. Compound 2 is the first example of an akuammicine-type alkaloid possessing an unprecedented 6/5/6/5/6/5 hexacyclic ring system. The new structures including their absolute configurations were elucidated on the basis of comprehensive spectroscopic data analyses, computational calculation methods, and X-ray diffraction analysis. Compound 2 exhibited potent vasorelaxant activity with an EC50 value of 6.3 μM. In addition, compound 5 exhibited moderate acetylcholinesterase (AChE) inhibitory activity with an IC50 value of 26.8 μM.