Schincarins G‒R: 3,4-secolanostane triterpenoids from the stems of Schisandra incarnata

Twelve previously undescribed 3,4-secolanostane triterpenoids, schincarins G‒R (1-12), were obtained from the methanol extract of the stems of Schisandra incarnata. Their structures and absolute configurations were determined based on spectroscopic analysis and single-crystal X-ray diffraction. Schincarins G and H represent the first examples of 3,4-secolanostane-type triterpenoids featuring a tricyclic 5/6/5 fused carbon skeleton. Schincarins M and Q exhibit moderate inhibition against ConA-induced T cell proliferation with IC₅₀ values of 20.5 and 20.0 μM, respectively, and against LPS-induced B cell proliferation with IC₅₀ values of 15.0 and 22.2 μM, respectively. Schincarin L demonstrates selective inhibition against LPS-induced B cell proliferation with IC₅₀ value of 24.1 μM.