The aim of this study consisted in extracting and quantifying phenolic and flavonoïds compounds of five selected Algerian plants. The second step was devoted to studying the effects of phenolic compounds on the kinetics catalyzed by two enzymes belonging to the class of hydrolase (the -amylase and the -glucosidase) responsible for the digestion of sugars. Finally, we assessed the potential antiradical of our extracts.The results indicate that the phenolic extracts from these plants have inhibitory effects on both enzymes, with K i values in g/ml range (18.19-72.14 g / ml) for the -amylase and (52.26 -203.90 g / ml) for -glucosidase. The antioxidant activity test shows that our phenolic extracts exhibit good antioxidant capacity comparatively to antioxidants taken as reference with IC 50 values which vary from 0.044 g / ml to 0.452 g / ml. This work contributes to understanding the role of natural polyphenols in the regulation of oxidative stress and normalization of glycemic disorders.

The aim of this study was to evaluate the antioxidant capacities of Cleome arabica leaves’ extract collected on two seasons in the town of Laghouat steppe region of Algeria. Five common tests for measuring antioxidant capacities were used to compare with three standard antioxidants: measurement of free radical scavenging activity with 1,1-diphenyl-2-picrylhydrazyl radical (DPPH·) and 2,2ʹ- azinobis(3-ethylbenzo-thiazo-line-6-sulfonate) (ABTS·+) radical cation, measurement of total antioxidant capacities with phosphomolybdenum, ferric reducing, and cupric reducing methods. The amount of the phenolic compounds was carried out by the quantification of total phenolic, total flavonoid, and condensed tannin contents in three organic solvents with varying polarities. The results show that the ethyl acetate is the best extractor solvent of flavonoids, while petroleum ether has the ability to extract more of terpenes. The values of quantification ranged from 0.341 to 0.751 mg of gallic acid equivalent/g of dry matter, from 0.172 to 0.682 mg of quercetin equivalent/g of dry matter and from 0.172 to 0.332 mg of catechin equivalent/g of dry matter for the total phenolic, flavonoids, and the condensed tannins, respectively. All the extract shows strong antioxidant activity, whose best are found in the ABTS and DPPH assay with IC50 values of 0.01 and 0.017 mg/ml, respectively, in a different season. These results suggest that the level of antioxidant activity in this plant varies to a great extent. They also suggest that phenolics in this plant provide substantial antioxidant activity. Upon achievement of this survey, an extra benefit of this medicinal plant may be found.

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In the present work, we have studied the inhibitory effects of aqueous and alcoholic extracts of six Algerian medicinal plants known by their therapeutic virtues against diabetes. The total phenolic compounds content, assayed using Folin-Ciocalteu's reagent, of the samples ranged from 0.183 mg/g to 43.088 mg/g and from 1.197 mg/g to 7.445 mg/g, expressed as gallic acid equivalent (GAE), for the, respectively, whereas the total flavonoids concentrations, detected using 2% of the aluminium chloride, ranged from 0.41 mg/g to 11.613 mg/g and from 0.0097 mg/g to 1.591 mg/g, expressed as rutin equivalents (RE), for the aqueous and methanolic extracts, respectively. The major plants were found to inhibit enzymatic activities of Aspergillus oryzae-amylase in a concentration dependent manner. The values of the inhibition constants ( ) have been determined according to the Dixon and Lineweaver-Burk methods. The results showed that the values were less than 55 ppm for the all extracts. A strong inhibition was found in the phenolic extract of Salvia officinalis with a of 8 ppm.

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