Immunosuppresive Sesterterpenoids and Norsesterterpenoids from <i>Colquhounia coccinea</i> var. <i>mollis</i>
Shu-Xi Jing, Ran Fu, Chun‐Huan Li, Tingting Zhou, Yanchun Liu, Yan Liu, Shi‐Hong Luo, Xiao‐Nian Li, Fang Zeng, Sheng‐Hong Li
Abstract
A pair of new C-14 epimeric sesterterpenoids, colquhounoid D (1) and 14-epi-colquhounoid D (2), and five degradation products featuring new C20 and C21 frameworks, norcolquhounoids A–E (3–7), were isolated from Colquhounia coccinea var. mollis. Their structures were elucidated by comprehensive spectroscopic analysis and single-crystal X-ray diffraction. Degradation of the C25 skeleton to the C21 skeleton was also achieved using aqueous NaIO4 and RuCl3. Compounds 1 and 2 showed significant immunosuppressive activity on the cytokine IFN-γ secretion of mouse splenocytes induced by anti-CD3/CD4 monoclonal antibodies, with IC50 of 8.38 and 5.79 μM, respectively, and compounds 5 and 6 were moderately active.