A pair of new C-14 epimeric sesterterpenoids, colquhounoid D (1) and 14-epi-colquhounoid D (2), and five degradation products featuring new C20and C21frameworks, norcolquhounoids A–E (3–7), were isolated from Colquhounia coccineavar. mollis. Their structures were elucidated by comprehensive spectroscopic analysis and single-crystal X-ray diffraction. Degradation of the C25skeleton to the C21skeleton was also achieved using aqueous NaIO4and RuCl3. Compounds 1and 2showed significant immunosuppressive activity on the cytokine IFN-γ secretion of mouse splenocytes induced by anti-CD3/CD4 monoclonal antibodies, with IC50of 8.38 and 5.79 μM, respectively, and compounds 5and 6were moderately active.