Effet de la méthode du séchage sur la teneur en composés phénoliques et les activités biologiques des feuilles de Moringa oleifera L.

Abstract

Moringa oleifera L. is a plant of nutritional and medicinal interest, very widespread through the tropical and subtropical areas. The present work aims to study the effect of different methods of drying of leaves of M. oleifera (free air, sun, oven and freeze-dried) on the content of phenolic compounds and the antioxydant and antibacterial activities. The extraction, carried out by maceration, gave extraction yields which differ according to the drying modes, vary from 23 to 28%. The phytochimic sifting showed a composition varied from secondary metabolites. The contents of phenolic compounds were determined, they vary according to the method of drying, where the extract of the leaves dried by drying oven reveals a higher content compared to the other extracts (contents of: polyphenols, flavonoïdes, condensed tannins are of 54.57 µg EAG/mg; 185 µg ER/mg;154 µg EC/mg of extract respectively). The antioxydant activity is evaluated by three tests: DPPH, ABTS and FRAP. The extract from the leaves dried by oven presented the best radical scavenging activity IC50 of 5616.78 and 2961.58 µg/ml respectively in the tests of the DPPH and the ABTS, and a reduction of the iron of 30.88 µg EAA/ml of extract. The antibacterial activity was evaluated by the method of diffusion in solid medium where all the extracts with various concentrations are active against two bacteria only; the extract of the leaves dried by oven has the best inhibiting activity opposite with the stock Pseudomonas aeruginosa with a diameter of 14.90 mm (12 mg/ml). The extract of the leaves dried by the free air presents the zone of the highest inhibition against the bacterium Streptococcus sp. (9.87 mm) whereas no effect of the four extracts was observed against the two other two strains (Staphylococcus aureus and Escherichia coli .