Nine previously undescribed immunosuppressive ent-labdane diterpenoids from the roots of Eurysolen gracilis

A detailed phytochemical investigation of the roots of Eurysolen gracilis (Lamiaceae) led to the isolation of nine previously undescribed ent-labdane diterpenoids (1-9), including two unprecedented 18(4→3)-abeo-ent-labdane-type diterpenoids (7 and 8). Their structures were unambiguously elucidated through extensive spectroscopic characterization (1D/2D NMR, HR-ESI-MS) and single-crystal X-ray diffraction analysis. All compounds were evaluated for their immunosuppressive activity in vitro. Notably, compounds 1 and 2 demonstrated inhibitory effects against IFN-γ production and T cell proliferation, with IC₅₀ values ranging from 6.30 to 15.03 μM.