ACTIVITES ANTILEISHMANIALE ET ANTIOXYDANTE DES EXTRAITS DE Securidaca longepedunculata (POLYGALACEAE).

Leishmaniasis is a neglected tropical parasitic disease that affects approximately 12 million people worldwide. Leishmania parasite mainly infect macrophages that released Reactive Oxygen Species (ROS) and Nitric Oxide (NO) as mean to control of the parasite infection. Chemotherapy remains the sole mean of disease management and relies on the use of molecules such as Amphotericin B, Glucantine and Miltefosine. However, these drugs are all confronted with many side effects and emergence of resistance strains. Medicinal plants represent an inexhaustible source of bioactive molecules against disease. Therefore, this work aimed at the evaluation of the antileishmanial and antioxidant activities of the methanolic, ethanolic, hydroethanolic and aqueous extracts of the bark of Securidaca longepedunculata.
The yields of extraction varied from 13.17% to 22.78% depending on the solvent used. The hydroethanolic and methanolic extracts of this plant exhibited good inhibitory activity on the promastigote forms of L. donovani with respective IC50s of 36.43 and 37.75 μg/ml. The phytochemical screening revealed the presence of total phenols, flavonoids, tannins, anthraquinones, terpenoids, alkaloids, coumarins, anthocyanins and saponins in both extracts. Besides, the hydroethanolic and methanolic extracts of the bark of the roots of the showed respectively a total flavonoid content of 27.20 and 25.70 mg of quercetin equivalent/g of crude extract, and in tannins of 267.66 and 219.9 mg of tannic acid equivalent/g of dry matter . The cytotoxicity test revealed that these two promising extracts are selective for macrophage cells and an inhibition on the intracellular amastigote form with IC50s of 74.62 and 59.55 µg/ml. It also results that the hydroethanolic extract has the ability to modulate the defense system of macrophages against the parasite by promoting the production of NO. These extracts exhibited anti-free radical activity on the DPPH radical with CP50 of 146.45 and 179.1 µg/ml and on the ABTS radical with CP50 of 81.58 and 31.98 µg / ml respectively and CP50 of 217, 65 and 189.55 µg/ml for iron reduction (FRAP). The results clearly show that the methanolic and hydroethanolic extracts of the bark of Securidaca longepedunculata (Polygalaceae) have antileishmanial and antioxidant properties and therefore constitute a source of biomolecule research for the fight against leishmaniasis caused by Leishmania donovani.
Keywords: S. longepedunculata, Antileishmanial activities, phytochemical screening, antioxidant.