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 muM in a dose-dependent manner in vitro. Especially, compound 3 exhibited potent activities comparable to positive control (Dexamethasone, DXM). CI - (c) 2021 Wiley-VHCA AG, Zurich, Switzerland.