(±)-Salvicatone A: A Pair of C(27)-Meroterpenoid Enantiomers with Skeletons from the Roots and Rhizomes of Salvia castanea Diels f. tomentosa Stib.

(±)-Salvicatone A (), a C-meroterpenoid featuring a unique 6/6/6/6/6-pentacyclic carbon skeleton with a 7,8,8a,9,10,10a-hexahydropyren-1 ()-one motif, was isolated from the roots and rhizomes of Diels Stib. Its structure was characterized by comprehensive spectroscopic analyses along with computer-assisted structure elucidation, including ACD/structure elucidator and quantum chemical calculations with H/C NMR and electronic circular dichroism. Biogenetically, compound was constructed from decarboxylation following [4 + 2] Diels-Alder cycloaddition reaction between caffeic acid and miltirone analogue. Bioassays showed that (-)- and (+)- inhibited nitric oxide production in lipopolysaccharide-induced RAW264.7 macrophage cells with an IC value of 6.48 ± 1.25 and 15.76 ± 5.55 μM, respectively. The structure-based virtual screening based on the pharmacophores in ePharmaLib, as well as the molecular docking and molecular dynamics simulations study, implied that (-)- and (+)- may potentially bind to retinoic acid receptor-related orphan receptor C to exert anti-inflammatory activities.