A new 7,9′-monoepoxylignan glucoside and other phytochemicals from Centaurea granatensis and their chemotaxonomic significance

Abstract

The chemical study of Centaurea granatensis Boiss. ex DC. allowed the isolation and structural elucidation of eighteen secondary metabolites (1-18) from ethyl acetate (EtOAc) and n-butanol (n-BuOH) extracts. These compounds are divided into one new epoxylignan glucoside (1) and seventeen known phytochemicals including seven flavonoids (2-8), four triterpenes (9-12), and six phytosterols (13-18). Structures of the isolates were identified using various spectroscopic methods, namely 1D NMR (1H and 13C), 2D NMR (HSQC, 1H-1H COSY, HMBC, and NOESY), and mass spectrometry (HR-ESIMS), as well as by comparison with literature data. The obtained results showed the abundance of triterpenoids and flavonoids particularly flavones in C. granatensis. Apigenin (3) could be used as a chemotaxonomic marker of this genus due to its presence in approximately forty plant species. Furthermore, tiliroside (2) and stigmasteryl-3-O-β-D-glucoside-6′-palmitate (18) were first detected in Centaurea genus, but had previously been found in species of the Asteraceae family. Additionally, the chemotaxonomic significance of all isolated molecules was fully discussed.