Incartrilactones A and B: Two schinortriterpenoids with a 14,15-seco-15,17-cyclolancifoartane skeleton from Schisandra incarnata

Abstract

In this study, incartrilactones A (1) and B (2), two previously undescribed schinortriterpenoids (SNTs) possessing an unprecedented 5/5/6/5/7/5-fused hexacyclic skeleton, together with one previously undescribed (3) and one known (4) analogues, were isolated from the stems of Schisandra incarnata Stapf. Their structures with absolute configurations were determined by comprehensive spectroscopic analysis, X-ray crystallography and electronic circular dichroism calculation. Compounds 1 and 2 represent the first class of 14,15-seco-15,17-cyclolancifoartane-type SNTs containing the unusual linkage of ‒C14‒C16‒C13‒C17‒C15. The hypothetical biogenetic pathway of compounds 1 and 2 was postulated. Compounds 1 and 2 exhibited potent α-glucosidase inhibitory activity with IC₅₀ values of 133.1 and 165.3 μM, representing that they were more active than the positive control, acarbose (IC₅₀ = 232.8 μM). Compound 4 showed moderate in vitro immunosuppressive effect against ConA-induced T cell and LPS-induced B cell proliferation, with IC₅₀ values of 35.3 ± 0.9 μM and 24.9 ± 0.6 μM, respectively. The cytotoxicity of compounds 1−4 against three human cancer cell lines was also tested, with no obvious cytotoxicity being observed.