Caractérisation phytochimique et évaluation in vitro de l'activité antioxydante de la gomme arabique

Abstract

The present study aims to valorize a natural exudate produced by the Acacia tree, harvested in the Taghit region (Béchar), an area that remains insufficiently explored to this day. To this end, a phytochemical characterization and an in vitro evaluation of the antioxidant potential of Algerian-origin gum arabic (GA) were carried out. Two extracts of GA were prepared by maceration: methanolic (GA-Meth) and hydro-ethanolic at 70% (GA-Hydro-Eth). Various quantitative and qualitative phytochemical analyses based on colorimetric chemical reactions were performed, along with a spectroscopic characterization of functional groups by FTIR-ATR. Thereafter, anti-radical assays (DPPH, FRAP, CAT) were conducted to assess the antioxidant potential of the studied extracts. Although the hydro-ethanolic extract yielded the highest mass yield (8.964% vs. 1.010%), methanol proved clearly superior for the extraction of active compounds. Indeed, the quantification of phenolic compounds revealed that the GA-Meth extract doubles the total phenolic content compared to the GA-Hydro-Eth extract (16.079 vs. 8.749 mg GAE/g DW), and shows markedly higher concentrations of flavonoids (3.234 vs. 0.409 mg QE/g DW), flavonols (0.38 vs. 0.051 mg QE/g DW), hydrolyzable tannins (11.05 vs. 5.25 mg TAE/g DW), and catechic tannins (2.15 vs. 0.748 mg CE/g DW). The saccharide fraction is also predominant in the GA-Meth extract, with high contents of total sugars (536.55 mg ME/g DW) and reducing sugars (218.365 mg ME/g DW). FTIR-ATR analysis confirmed the presence of key functional groups (hydroxyl, carbonyl, and aromatic groups). This chemical richness confers excellent antioxidant activity to the methanolic extract, which proved superior across all assays performed: DPPH (IC₅₀ = 2.45 mg/mL, undeterminable for the hydro-ethanolic extract), FRAP (308.3 vs. 9.909 μmol FeSO₄·7H₂O/L DW), and CAT (63.605 vs. 12.474 mg AAE/g DW). This work paves the way for detailed identification by HPLC-MS and for the optimization of extraction protocols. In the long term, it represents a scientific step toward integrating gum arabic from Taghit (Algeria) as a natural bioactive ingredient in the development of new antioxidant pharmaceutical and biomedical formulations, aimed at preventing oxidative stress and targeting chronic pathologies.