Recherche d'activités antioxydante, antimicrobienne et antidiabétique de deux plantes du Sud-Ouest de l'Algérie: Traganum nudatum et Ammodaucus leucotrichus

Abstract

Ammodaucus leucotrichus Cosson & Durieu and Traganum nudatum Delile are widely used in traditional pharmacopoeia in Algeria to treat many diseases including diabetes mellitus. The aim of this work is to conduct a phytochemical study and a search for antioxidant, antimicrobial and antidiabetic activities of the hydromethanolic crude extracts and their ethyl acetate and n-butanol fractions of each plant. The phytochemical screening revealed the presence of flavonoïds, tannins, alkaloïds, quinones, saponins and terpenoïds in the extracts of both plants. The highest contents of polyphenols and flavonoïds were attributed to the ethyl acetate fraction of the crude hydromethanolic extract prepared by infusion FAcI of T. nudatum of (415.32 ± 0.3) mg GAE / g and (92.58 ± 1.8) mg CATE / g respectively, while the ethyl acetate fraction of the crude hydromethanolic extract prepared by maceration FAcM of the same plant was found to be the richest in flavonols of (302.88 ± 0.92) mg QE / g. A. leucotrichus has shown low contents of polyphenols, flavonoïds and flavonols. The evaluation of the antioxidant activity was carried out by three techniques: DPPH, TAC and FRAP assays. For the DPPH assay, FAcM of T.nudatum presented the lowest IC50 of (20 ± 0.11 μg / ml), the n-butanol fraction of the hydromethanolic crude extract prepared by maceration Fn -BM of the same plant showed the highest total antioxidant capacity of (200.21 ± 0.2) mg AAE / g, the best reducing activity was exhibited by FAcM of A. leucotrichus with an EC50 of (24 ± 1.1 μg /ml). The evaluation of the antimicrobial activity was carried out on reference microorganisms by two techniques: the diffusion and dilution methods. For the first technique, the extracts of T. nudatum demonstrated inhibition diameters between 7 and 14 mm, the most interesting activity was noted in the ethyl acetate fractions FAcM and FAcI, the most sensitive strains were B.cereus, B.subtilis, L.monocytogenes, P.mirabilis and S.uareus with the highest inhibition diameters and the lowest MICs. The extracts of A. leucotrichus showed zones of inhibition which do not exceed 10 mm of diameter, the strongest activities were evident in FAcM and FAcI notably against B.cereus, B.subtilis, A. baumannii, L.monocytogenes, M.luteus and S.aureus. Generally, Gram-positive bacteria were the most sensitive to the extracts of both species. However, the extracts of both species did not show any antifungal activity. The identification of phenolic compounds by HPLC of ethyl acetate and n-butanol fractions revealed the presence of sinapic, syringic, ferulic and p-coumaric acids, naringenin, catechin and vanillin in T. nudatum and sinapic acid, ferulic acid, pcoumaric acid, quercetin, naringenin and vanillin in A. leucotrichus. The results of the antidiabetic activity in vivo revealed a highly significant antihyperglycaemic effect by the crude hydromethanolic extract prepared by maceration EBM of T. nudatum and its fraction FAcM of 25.66 % and 59, 39 % at the second and the third week of treatment respectively. A highly significant reduction in blood glucose level was also exhibited by EBM of A. leucotrichus of 14.92%, this reduction was not significant for FAcM of 27.48% after four weeks of treatment. In vitro antidiabetic analysis revealed a highly significant liver glucose uptake stimulation of 47.6% and 48% for EBM and FAcM of A. leucotrichus and 42% and 44% for EBM and FAcM of T. nudatum after 90 minutes of incubation, a very significant