Etude phytochimique et évaluation des activités antioxydante et antibactérienne des extraits de Orobanche aegyptiaca Pers.

Abstract

Orobanche aegyptiaca Pers. is a medicinal holoparasitic plant belonging to the Orobanchaceae family, commonly known by the vernacular name “El-Danone” and widely used in traditional medicine. The aim of this work is to carry out a phytochemical study and to evaluate the antioxidant and antibacterial activities of the plant extracts. The extraction of bioactive compounds from the aerial parts of the plant was performed using Soxhlet extraction with two solvents of different polarities: methanol and hexane yielding 21.04% and 1.56% for the methanolic and hexanic extracts, respectively. Quantitative analysis of total polyphenols, carried out using the Folin–Ciocalteu method, and flavonoids, determined by the aluminum chloride (AlCl₃) method, showed that the methanolic extract was the richest in phenolic compounds, with contents of 169.81 ± 3.18 µg GAE/mg extract for polyphenols and 11.64 ± 0.86 µg QE/mg extract for flavonoids. The in vitro antioxidant activity of the extracts was evaluated using four methods: total antioxidant capacity (TAC), DPPH and ABTS radical scavenging assays, and reducing power assay. The results demonstrated that the methanolic extract possessed a good antioxidant capacity (TAC = 197.81 ± 2.04 µg AAE/mg extract). In addition, this extract exhibited significant free radical scavenging activity against DPPH and ABTS radicals, with IC₅₀ values of 36.77 ± 0.96 µg/mL and 30.07 ± 2.10 µg/mL, respectively. It also showed a good reducing power with an A 0,5 value of 220.55 ± 3.03 µg/mL. The antibacterial activity was evaluated using the microdilution method in liquid medium on microplates. The obtained results showed that the methanolic extract exhibited greater antibacterial activity than the hexanic extract. The most sensitive bacterial strain was Escherichia coli, with MIC and MBC values of 31.25 mg/mL and 62.5 mg/mL, respectively. In conclusion, these results support the traditional use of this plant and open up prospects for future therapeutic applications.