Etude comparative de la composition chimique et de l’activité antioxydante d’une plante médicinale récoltée dans différentes régions d’Algérie.

Abstract

This work is a comparative phytochemical study of a medicinal plant belonging to the Lamiaceae family collected from three regions in Algeria: Djelfa (PD), Batna (PB), and Sétif (PS). It aims to determine the chemical composition, total phenolic and flavonoid contents, as well as the antioxidant activity in order to evaluate the influence of geographical origin. Phytochemical screening revealed that all three samples are rich in secondary metabolites, including saponins, polyphenols, condensed tannins, triterpenes, sterols, flavonoids, coumarins, anthocyanins, and anthraquinones, with variations according to the regions, while alkaloids and gallic tannins were absent. The highest extraction yield was observed for PD (14.95%), followed by PS (10.5%) and PB (8.3%). Total phenolic contents were highest in PD (168.89±16.34 mg GAE/g of extract), followed by PB (145.67±6.44 mg GAE/g of extract) and PS (110.17±7.55 mg GAE/g of extract). In contrast, total flavonoid contents were higher in PS (15.92±0.85 mg QE/g of extract) compared to PD and PB. Antioxidant activity varied depending on the assays performed. In the DPPH assay, PS showed the highest activity (IC50 = 0.0146±0.00011 mg/mL), followed by PD and PB (0.0277 mg/mL), with a strong correlation with flavonoids (R² = 0.875). In the ABTS•+ assay, PD and PS showed close activities (0.0059 ± 0.00135 and 0.0068±0.00135 mg/mL), higher than PB (0.0167±0.00015 mg/mL), with a weaker correlation with flavonoids (R² = 0.4052). The results indicate that flavonoids contribute variably to antioxidant activity depending on the assay used, suggesting the involvement of other bioactive compounds.