A New Monoterpene Alkaloid From the Stems of Rauvolfia vomitoria

One new monoterpene alkaloid (1) and eight known compounds (2-9), belonging to two monoterpene alkaloids (1-2), one pyridine alkaloid (3), four phenylpropanoid derivatives (4-7), and two matrine-type alkaloids (8-9), were isolated from Rauvolfia vomitoria Afzel. The structure of new compound 1 was determined by extensive spectroscopic analysis and electronic circular dichroism (ECD) calculation. Notably, this is the first reported monoterpene alkaloids from R. vomitoria. Besides, compounds 3, 5, and 7-9 were first discovered in the Apocynaceae family and compounds 4 and 6 were first reported in the Rauvolfia genus. This is also the first example of matrine-type alkaloids reported in the Apocynaceae family, indicating that matrine-type alkaloids are not unique to the Leguminosae/Fabaceae family. All isolated compounds were evaluated for their anti-acetylcholinesterase, anti-alpha-glucosidase, and antioxidant activities. Compound 6 showed significant alpha-glucosidase inhibitory activity and remarkable DPPH radical scavenging capacity, both of which are superior to the positive controls. Molecular docking of compound 6 with alpha-glucosidase was further performed, suggesting that compound 6 could form hydrogen bonds with residues ALA-292, ASN-259, and ARG-263.