Two New Koumine-Type Indole Alkaloids from Gelsemium elegans Benth.

Two new indole alkaloids, 21-oxokoumine ( 1) and furanokoumine ( 2), were isolated from the roots of Gelsemium elegans Benth together with three known compounds. The structures of the two novel compounds were elucidated by spectroscopic methods, including NMR, HR-ESI-MS, UV, IR, CD and molecular modeling. Compound 1 is the first instance of a koumine-type alkaloid with a carbonyl at the C-21 position, while compound 2 possesses a tetrahydrofuran ring located on C-20 and C-21.