Caractérisation, Comportement Rhéologique Et Activités Biologiques De Polysaccharide Hydrosoluble Issu Des Graines De Plantago Ciliata Desf. Récoltées Dans La Région De Ghardaïa (sahara Septentrional Est Algérien)

Résumé: Plantago ciliata Desf., a spontaneous medicinal plant widespread in Ghardaïa province (East Septentrional Algerian Sahara). However, little is know about the active components imparting therapeutic properties to the plant. The present study focuses on structural, physico-chemical characterization and biological properties of a novel water-soluble polysaccharide (PSPC). P. ciliata seeds consisting of 18.6% (w/w) of mucilaginous fraction, rich in total sugars (86.5 ± 4.32%). Results led to the identification of a neutral arabinoxylan with a high molecular weight of 700 kDa, mainly composed of β-(1,3)-D-Xylp backbone including also residues of β-(1,4)-D-Xylp. The backbone might be substituted to O-2 and O-3 with α-L-Araf residues, and T-Xylp throught O-3 positions. The rheological properties of PSPC in semi-diluted regime are characteristic of a pesudoplastic fluid with a weak gel behavior may be used as a thickening agent in the food industry. The critical overlay concentration (C*) was estimated from 3.2 to 3.7 g.L-1. In ethnobotany, P. ciliata and their extracts are widely used to treat diabetes and diseases often associated with inflammation, whose biological potential has been assessed on PSPC polysaccharide. The anti-inflammatory effect of PSPC was measured by the reduction of two enzymes activities; NADPH oxidase (NOX2) and myeloperoxidase (MPO) of human neutrophils stimulated by phorbol 12-myristate 13-acetate. PSPC shows dose-dependent inhibition, with IC50 of 111 μg.mL-1 and 203 μg.mL-1 for NOX2 and MPO, respectively, appearing to be more effective than the negative control. In order to evaluate the anti-hyperglycemic activity of PSPC, the inhibition of two digestive enzymes α-amylase and α-glucosidase was measured in vitro. PSPC is an effective inhibitor of α-amylase with an IC50 of 3.60 mg.mL-1 as compared to 0.30 mg.mL-1 for acarbose. Whereas, the PSPC hydrolysate adjusted strongly the inhibitory power of α-glucosidase and showed an IC50 of 4.71 mg.mL-1 against 10 mg.mL-1 for native PSPC. This current study has provided original structural information, rheological behaviour and biological properties of a new arabinoxylan belonging to psyllium (Plantaginaceae) in view of its industry application as a bioactive adjuvant.

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