Spectrometric analysis, phytoconstituents isolation and evaluation of in vitro antioxidant and antimicrobial activities of Tunisian Cistanche violacea (Desf)

The Orobanchaceae plant Cistanche violacea (Desf) Hoffmanns & Link stands for one of the authorized Cistanche plant resources. The antioxidant activity of different extracts (hexanic, EtOAc, MeOH and acetone–water extracts) of C. violacea aerial part and underground stems was determined using five in vitro techniques. Extracts were screened for their antimicrobial activity by disk diffusion assay and microdilution methods. The MeOH extracts displayed the highest activity. Their bactericidal and fungicidal effects on most of the tested strains proved to be reasonable. The phytochemical screening of total flavonoids and identified phenolic acids was greatly discrepant and showed an abundance of phenolic acids in all extracts as performed by liquid chromatography–electrospray ionization mass spectrometry (LC–ESI–MS). The content of 3,4-di- O -caffeoylquinic acid (from 2400 to 13,000 ppm) was higher in the underground stems as compared with the aerial part (from 0 to 2800 ppm). Conversely, in the aerial part, apigenin was abundant with concentrations ranging between 816 and 3525 ppm. Its concentration in the stems varied between 35 and 206 ppm. The chemical treatment of three extracts of the aerial part allowed the isolation of five products, namely Sesamin, β -sitosterol, Tricin, β -sitosterol-3- O - β -D-glucoside and Mannitol. These products were characterized using advanced nuclear magnetic resonance and identified for the first time in the genus Cistanche . Four compounds exhibited good antioxidant activity and low sensitivity of the tested microorganisms, while the β -sitosterol was the most active and exhibited a higher sensitivity against most strains (varying from 11 to 20 mm). Graphical abstract