Evaluation du pouvoir antioxydant et antimicrobien des extraits végétaux (cas de la grenade Punica granatum L.) en vue de leur utilisation alimentaire

Abstract

The purpose of this study is to evaluate the antimicrobial and the antioxidant pomegranate (Punica granatum L.) peel extract (PPE) of in vitro and the oxidative stability of sunflower oil and soybean oil stabilized by this extract during accelerated storage. The results showed that the PPE is very rich in total polyphenols (448.4 mg/g GAE), flavonoids (30.37 mg/g QE) and hydrolysable tannins (374,37 mg/g TAE). It is effective against Staphylococcus a., Bacillus s., Pseudomonas a., Klebsiella p. bacteria growth and gave inhibition zones diameters that vary between 10 to 26 mm and MIC values ranging between 62.5 and 500 mg/ ml. The PPE showed a high antioxidant activity: The IC50 (DPPH test) obtained for A. Ascorbic, PPE, BHT, and α-tocopherol are respectively: 2.903 ± 0.002, 5.49 ± 0.039, 7.113 ± 0.166, 28.15 ± 0.767 µg / mL. The EC50 (reducing power) were: 11.05 ± 0.01, 25.78 ± 0.10, 26.74 ± 0.17, 49.95 ± 0.01 µg / mL, respectively. A high inhibition activity of peroxidation at 0.5 mg / ml following the order: BHT ≈ EPG ˃ α-tocopherol. High chelating activity but less than the EDTA’s. The results of oxidative stability of oils indicate that the PPE showed a higher antioxidant activity than that of the BHT (200 ppm) in sunflower oil (500 and 1000 ppm) and the same activity in soybean oil (1000 ppm). Therefore, this study indicates that the pomegranate peel extract can be considered as a good source of natural compounds with antioxidant activity and antimicrobial and used in the food industry as a preservative in multi-functional food products.