Antiproliferative and Pro-apoptotic Effects of Sesquiterpene Lactones from Schkuhria pinnata in THP‑1 Leukemia Cells.

As Schkuhria pinnata is a food supplement commonly available on the European market, the aqueous-methanol extract from the aerial parts of S. pinnata was subjected to chromatographic separation to isolate compounds with antiproliferative and pro-apoptotic properties. This procedure led to the isolation of two previously undescribed sesquiterpene lactones (1 and 2) bearing an unusually modified germacranolide skeleton, four known heliangolides (3-6), together with flavonoids hispidulin and pectolinarigenin. The structures of isolated compounds were elucidated by a comprehensive analysis of HRMS and 1D and 2D NMR data. Sesquiterpene lactones (1-6) were evaluated for their antiproliferative activities in the THP-1, DU-145, and MCF-7 cancer cell lines. Compounds 3-6 showed an antiproliferative effect with the highest intensity in the THP-1 leukemic cell line. The most effective compound 5, 2″-dehydroeucannabinolide semiacetal, induced apoptosis and loss of mitochondrial membrane potential, increased mitochondrial superoxide production, and suppressed mitochondrial ATP production in THP-1 cells.