Structural, antioxidant and antibacterial activities of polysaccharides extracted from olive leaves

In the present study, hot-water extraction procedure was used to recover polysaccharides from olive leaves. Primary structural characteristics were determined by nuclear magnetic resonance spectroscopy (1H NMR and 13C NMR), Fourier Transform-Infrared spectroscopy (FT-IR) and X-ray diffractometry analysis. Emulsifying capacity, Zeta (ζ) potential and differential scanning calorimetric (DSC) of olive leaf polysaccharides (OLP) were investigated. Antioxidant and antibacterial activities were then examined. Infrared spectroscopy data revealed that OLP were constituted of functional groups OH, CO and CH which were specific to polysaccharides. Results of ζ-potential showed that OLP possessed an anionic structure and exhibited donated electron capacities. OLP displayed strong DPPH-radical scavenging activity (IC 50 = 34.80 μg/mL). They showed also important reducing power and β-carotene bleaching inhibition activities. Besides, OLP have attractive antibacterial activity against S.enterica and M.luteus with inhibition zones of 23.5 and 21.5 mm, respectively.