• antioxidant activity
• Atriplex halimus L.
• glycosylated flavonoids

The halophyte Atriplex halimus L., belonging to the Amaranthaceae family, has been used for centuries in the Mediterranean basin as food and medicinal source. Previous studies revealed its extracts are rich in secondary metabolites such as flavonoids, phenolic acids, and saponins and exert antidiabetic, antimicrobial and antioxidant activities. The aim of the present work was to analyse the chemical composition of the extracts from the aerial parts of A. halimus L. and assess their antioxidant activity. The plant material was sequentially extracted with n-hexane, CHCl3, CHCl3-MeOH (9:1) and MeOH. The MeOH extract was then partitioned between n-BuOH and water. The n-BuOH extract was fractionated by size exclusion chromatography and individual fractions were further separated by semipreparative HPLC to afford pure compounds, characterised by NMR and HR-ESIMS analyses. For antioxidant activity DPPH, ORAC, and CAA-RBC assays were performed. The isolation process yielded 15 compounds, including 5 new ones. Most compounds are glycosylated flavonols with long, branched or linear, sugar chains, sometimes esterified with ferulic or p-coumaric acid. Among the extracts, the n-BuOH showed the highest antioxidant activity In DPPH and ORAC assays, while both the n-BuOH and MeOH extracts were active in the cellular assay. The antioxidant activity of the pure compounds tested ranged from 10.4 ± 0.12 to 62.6 ± 2.8 µM (IC50) for DPPH, from 3.56 ± 0.22 to 7.1 ± 0.35 µmol TE/µmol for ORAC, and from 43 ± 1.7 to 84.2 ± 0.87 % of quercetin CAA units for CAA-RBC assay. In conclusion, A. halimus L. is rich in flavonoids with unusual structures and marked antioxidant activity, making it an interesting candidate for the development of new nutraceutical products.