Evaluation de l’activité antioxydante des feuilles de Moringa oleifera Lam. (Moringaceae) du Sénégal

Les plantes medicinales telles que Moringa oleifera, presentent en general de nombreuses vertus therapeutiques. L’objectif de cette etude etait d’evaluer l’activite antioxydante des extraits des feuilles de Moringa oleifera par la methode de piegeage des radicaux libres 2,2-diphenyl-1- picryl-hydrazyle (DPPH•). Une extraction ethanolique a ete effectuee et l’extrait sec obtenu a ensuite ete fractionne par la methode de separation liquide-liquide avec des solvants polaires (eau distillee et acetate d’ethyle) et apolaires (dichloromethane). L’extrait ethanolique, ses fractions et l’acide L-ascorbique (antioxydant de reference), ont ete testes a differentes concentrations: 12,5; 25; 50; 100 et 200 μg/ml. La lecture de l’absorbance des produits s’est faite au bout de 30 minutes au spectrophotometre a 517 nm. Il ressort de cette etude que l’extrait ethanolique des feuilles de Moringa oleifera et ses differentes fractions possedent une activite antioxydante significative qui est dose-dependante.Cependant, l’activite la plus importante a ete observee avec l’extrait ethanolique avec une concentration inhibitrice 50 (CI50) de 87,86±1,80 μg/ml. Les resultats de cette etude suggerent que les feuilles de Moringa oleifera contiennent des substances a proprietes antioxydantes qui pourraient contribuer a la prevention de certaines maladies chroniques telles que le cancer, les maladies cardiovasculaires entre autres. © 2018 International Formulae Group. All rights reserved. Mots cles: Moringa oleifera , activite antioxydante, fractionnement, DPPH English Title:  Evaluation of the antioxidant activity of leaves of Moringa oleifera Lam. (Moringaceae) of Senegal English Abstract Medicinal plants such as Moringa oleifera generally have several therapeutic virtues. This study aimed to evaluate the antioxidant activity of Moringa oleifera leaves extracts using the free  radical scavenging method: 2,2-diphenyl-1-picryl-hydrazyl (DPPH•) assay. Ethanolic extraction was carried out and the dry extract obtained was then fractionated by the liquid-liquid separation method with polar solvents (distilled water and ethyl acetate) and non polar solvent (dichloromethane). The antioxidant activities of the ethanolic extract, its fractions and the Lascorbic acid (reference antioxidant) were tested at various concentrations of 12.5; 25; 50; 100 and 200 μg/ml. The absorbance of the products was read after 30 minutes at the spectrophotometer at 517 nm. It emerged from this study that the ethanolic extract of Moringa oleifera leaves and its different fractions had significant antioxidant activity that is dose-dependent. However, the ethanolic extract was more active on DPPH radical inhibition with a concentration of sample required to scavenge 50% of free radicals (CI50) of 87.86 ± 1.80 μg/ml. These results suggest that leaves of Moringa oleifera contain substances with antioxidant properties that could contribute to the prevention of chronic diseases such as cancer, cardiovascular diseases, among others. © 2018 International Formulae Group. All rights reserved. Keywords: Moringa oleifera , antioxidant activity, DPPH