Contribution à l’étude des polysaccharides de deux plantes spontanées récoltées au Sahara septentrional Est Algérien (région d’El Oued)

Abstract

La présente étude s'oriente sur l’étude des polysaccharides issus de deux plantes spontanées à caractère médicinal récoltées au Sahara septentrional Est Algérien de la région d’El Oued. Il s’agit d’Oudneya africana (Brassicaceae) et d’Ephedra alata (Ephedraceae). Pour l’étude de la composition chimique des polysaccharides, ainsi que pour évaluer leurs activités anti-oxydante et antidiabétique, les extraits polysaccharidiques sont obtenus par macération à chaud dans de l'eau distillée. Les rendements massiques des extractions des polysaccharides hydrosolubles des feuilles (OAL) et des fruits (OAF) d’Oudneya africana et des feuilles d’Ephedra alata (EAL), sont de 14,5%, 6,05% et 8,3% respectivement. L’étude de la composition biochimique des extraits polysaccharidiques montre que les oses neutres sont les constituants majeurs de toutes les fractions. Il est noté des teneurs en oses réducteurs et en polyphénoles totaux nulles dans toutes les fractions étudiées. Après une hydrolyse par l’acide trifluoroacétique, la chromatographie sur couche mince (CCM) indique l'arabinose et le glucose comme oses constitutifs communs pour les trois fractions. L’étude de l’activité antioxydante des polysaccharides a révélée des pourcentages d'inhibition des radicaux DPPH de 86,21% (OAL), 85,55% (OAF) et 77,49% (EAL). L’activité antidiabétique des extraits polysaccharidiques, porte sur la détermination de leur pouvoir inhibiteur de l’enzyme α-D-glucosidase. L’étude a montré que la fraction OAL présente le pouvoir inhibiteur de l’α-D-glucosidase remarquable, soit 77,67%, pour une concentration de 100 mg/ml.The present study focuses on the study of polysaccharides from two spontaneous medicinal plants harvested in the northern Algerian Sahara of the El Oued region, including Oudneya africana (Brassicaceae) and Ephedra alata (Ephedraceae). The aim of this work is to study the chemical composition of polysaccharides, thus to evaluate their antioxidant and antidiabetic activities. The polysaccharide extracts are obtained by hot maceration in distilled water. The mass yields extaction water soluble polysaccharide of Oudneya africana (OAL) and fruit (OAF) extracts and Ephedraalata leaves (EAL) were 14.5%, 6.05% and 8.3%, respectively. The study of the biochemical composition of polysaccharide extracts shows that neutral oses are the major constituents of all fractions. Reducing ose and total polyphenol contents are noted in all fractions studied. After hydrolysis with trifluoroacetic acid, The analysis by thin layer chromatography (TLC) indicated arabinose and glucose as the common constituent compounds for all three fractions. The study of the antioxidant activity of the polysaccharides revealed percentages of inhibition of the DPPH radicals of 86.21% (OAL), 85.55% (OAF) and 77.49% (EAL). The antidiabetic activity of the polysaccharide extracts relates to the determination of their inhibitory power of the α-D-glucosidase enzyme. The study showed that the OAL fraction has the most remarkable inhibitory α-D-glucosidase power of 77.67% for concentration of 100 mg / ml.

The present study focuses on the study of polysaccharides from two spontaneous medicinal plants harvested in the northern Algerian Sahara of the El Oued region, including Oudneya africana (Brassicaceae) and Ephedra alata (Ephedraceae). The aim of this work is to study the chemical composition of polysaccharides, thus to evaluate their antioxidant and antidiabetic activities. The polysaccharide extracts are obtained by hot maceration in distilled water. The mass yields extaction water soluble polysaccharide of Oudneya africana (OAL) and fruit (OAF) extracts and Ephedraalata leaves (EAL) were 14.5%, 6.05% and 8.3%, respectively. The study of the biochemical composition of polysaccharide extracts shows that neutral oses are the major constituents of all fractions. Reducing ose and total polyphenol contents are noted in all fractions studied. After hydrolysis with trifluoroacetic acid, The analysis by thin layer chromatography (TLC) indicated arabinose and glucose as the common constituent compounds for all three fractions. The study of the antioxidant activity of the polysaccharides revealed percentages of inhibition of the DPPH radicals of 86.21% (OAL), 85.55% (OAF) and 77.49% (EAL). The antidiabetic activity of the polysaccharide extracts relates to the determination of their inhibitory power of the α-D-glucosidase enzyme. The study showed that the OAL fraction has the most remarkable inhibitory α-D-glucosidase power of 77.67% for concentration of 100 mg / ml.