New alkaloids from the twigs and leaves of tabernaemontana divaricata and their neuroprotective effects

Two novel monoterpenoid quinoline alkaloids, tabernacatines A and B (1 and 2), and a new monoterpenoid indole alkaloid, tabernacatine C (3), along with three known alkaloids (4 − 6), were isolated from the twigs and leaves of Tabernaemontana divaricata. Their structures were elucidated based on UV, IR, HR-ESI-MS, NMR spectra analysis, X-ray diffraction, and ECD calculation methods. Compounds 1 − 6 were evaluated for their neuroprotective effects in glutamate-induced HT22 cells, and compounds 4–6 exhibited potent neuroprotective effects.