Two amino acid-sesquiterpene lactone conjugates from chicory roots and their anti-inflammation activity

Cichorium intybus L. is a member of the Cichorium genus within the Asteraceae family; it has been historically utilised for both nutritional and therapeutic purposes across various cultures. Sesquiterpene lactones are recognised as its primary bioactive components. In this study, an amino acid-sesquiterpene lactone conjugate cluster was discovered for the first time in chicory roots. Two of them were then isolated including a new compound, 11β, 13-dihydro-13-prolyl-lactucin (1). Structural determination was achieved through extensive spectroscopic studies. The absolute stereochemistry of compound 1 was deduced by matching its experimental ECD spectrum with the theoretically predicted one. In addition, anti-inflammatory activity test demonstrated that both two compounds showed evident NO production inhibitory effects in LPS-induced RAW264.7 macrophages, the IC₅₀ of compound 1 was 20.14 µM. Furthermore, it downregulated the expression of inflammatory factors TNF-α, IL-6 and COX-2.