Isolation and structure elucidation of two new antioxidant flavonoid glycosides and fatty acid composition in Hedysarum carnosum Desf.

• The fractionation of Hedysarum carnosum butanol extract was investigated.
• This extract resulted in the isolation of two new flavonoids 1 and 2 and a known compound 3 but indicated for the first time in this specie.
• The crude extract, its fractions and the isolates exhibited promising antioxidant activity.

The present work constitutes a contribution to the phytochemical investigation of Hedysarum carnosum aiming to search for novel bioactives secondary metabolites. In this context, the fractionation of the butanolic extract of H. carnosum flowers afforded two new flavonoid glycosides quercetin 3-O-β-d-glucopyranosyl-(1 → 2)-α-l-rhamnopyranosyl-(1 → 6)-α-l-rhamnopyranoside 1 and kaempferol 3-O-β-d-glucopyranosyl-(1 → 2)-α-l-rhamnopyranosyl-(1 → 6)-α-l-rhamnopyranoside 2 together with a the known rutin 3 indicated for the first time in this species. Their structures were determined on the basis of spectroscopic evidences (UV, HRMS and NMR) and comparison with literature. The fatty acid composition of the hexane extract of this species was also investigated by using GC–MS. The n-butanol extract and the isolates were assessed for their antioxidant potential using DPPH and ABTS+ scavenging assays and ferric reducing power (FRAP). The n-butanol extract and its fractions exhibited efficient radical scavenging activity with IC50 values ranging from 16 to 37 μg/mL for the DPPH assay. The obtained results suggest that the isolated compounds 1 and 3 could be promising antioxidant agents.

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