4,21‐Secovincanol, a Novel Immunosuppressive Monoterpenoid Indole Alkaloid from Kopsia Hainanensis

4,21‐Secovincanol (1), a novel C‐21/N‐4 cleavage monoterpenoid indole alkaloid, along with four analogs (2–5), were obtained from the aerial parts of Kopsia hainanensis. Structurally, compound 1 might be a derivative of epivincanol (2) via C‐21/N‐4 cleavage. Their structures were confirmed by means of comprehensive spectroscopic data analysis and comparison with the reported data. All isolates significantly inhibited Con A‐stimulated mice splenocytes proliferation at 10–40 μM in a dose‐dependent manner in vitro. Especially, compound 3 exhibited potent activities comparable to positive control (Dexamethasone, DXM).