Clerodane diterpenoids from the Uygur medicine Salvia deserta with immunosuppressive activity

Six undescribed clerodane diterpenoids along with five known ones were isolated from the aerial parts of Salvia deserta, a traditional Uygur medicine. Their chemical structures including absolute configurations were elucidated by extensive spectroscopic analysis (including 1D and 2D NMR, HRESIMS, and IR), combined with calculated ECD method and single-crystal X-ray diffraction analysis. All the compounds possessed a terminal α,β-unsaturated-γ-lactone moiety, and were assayed for their immunosuppressive activity via inhibiting the secretion of cytokines TNF-α and IL-6 in macrophages RAW264.7. Among them, (5R,8R,9S,10R)-18-nor-cleroda-2,13-dien-16,15-olide-4-one obviously suppressed the secretion of TNF-α and IL-6 with IC₅₀ values of 8.55 and 13.65 μM, respectively.