Evaluation De L’activité Antioxydante Et De L’effet Anticorrosif Des Extraits Phénoliques De Plantes Locales (plantago Ciliata Et Thymelia Microphylla)
Résumé: This work is structured around two axes. The first part is focused on the phytochemical characterization of two medicinal plants in the Laghouat region: Plantago ciliata and Thymelaea microphylla, and the second one is concentrated in the anti-corrosive effect of these plants extracts. The antioxidant capacity of aerial parts extracts of Plantago ciliata and Thymelaea microphylla has been studied. The quantitative estimation of total phenolics and flavonoids revealed that Thymelaea microphylla had the highest total phenolic content (12.33 ± 0.01-4.35 ± 0.04 mg GAE / g) and flavonoids (5.2 ± 0.08-1.09 ± 0.05 mg CaE / g) when compared to Plantago ciliata extracts. However, the highest total phenolic and flavonoids contents were obtained using methanol/water (80/20) as extraction solvent system. The antiradical power measured by the DPPH assay showed that PM3 extract exhibited significantly higher antioxidant effect when compared with standard antioxidants (BHA, Vit. C and Vit. E) with an EC50 value equal to 3.50 ± 0.05 mg / l. On the other hand, all tested extracts revealed reducing powers measured by the PPM method higher than standard antioxidants. The second part of this work was focused to the evaluation of the inhibitory effect of PM3 and TM3 extracts on the corrosion of XC52 steel in 1M HCl acid medium. The results of mass loss for the corrosion inhibition proved that the maximum efficiency obtained by the PM3 extract was 53.57% at a concentration of 5 ppm, and 58.91% for the TM3 extract at 5 ppm. In addition, the inhibitory efficacy of the extracts by the Tafel method proved that PM3 extract is the most effective at the concentration of 20 ppm with an inhibitory efficiency equal to 60.58%. In the impedance method, the inhibitory yield increases with the concentration of the extracts which reaches the value of 83.07% at 25 ppm for the PM3 extract and 79.46% at 20 ppm for the TM3 extract. Finally, the adsorption of the inhibitors (PM3 and TM3) from HCl solution on the steel surface obeys the Langmuir adsorption isotherm.
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