Etude phytochimique d'une plante médicinale

Abstract

Phytochemical study of a medicinal plant: Fraxinus angustifolia Vahl. Study of some biological activities A relatively few studies have been accomplished on the pharmacological activities of Fraxinus angustifolia Vahl specie. Accordingly, contributing to a new medicinal potentialities research of the study plant was the aim of this current work. To this end, the leaves were subjected to three different extraction methods : simple hydrodistillation, decoction, and exhausting extraction in a Soxhlet apparatus. As a result, essential oil, aqueous crude extract, and by the same process both crude methanolic and petroleum ether extracts were respectively obtained as the four extractable products used in this study. The extraction yield varies from 0,03 to 43,03 %. The phytochemical investigations done on the crude extracts by characterization reactions revealed the presence of tannins, flavonoids, saponosides, cardiotonic glycosides, reducing compounds and mucilages, which justify the Fraxinus angustifolia Vahl. employment in traditional medicine. The crude extracts content of total polyphenolic compounds also was estimate, using the colorimetric determination according to the Folin-Ciocalteu method. The polyphenolic content varies from 28.85 to 133.14 mg EAG / g. Thereafter, biological investigations were carried out on the first in vitro evaluation of antiparasitic potential of these extractable products, as well as on the in vitro evaluation of their antioxidant potential. The antileishmanial activity assessment has identified the petroleum ether extract and the essential oil as the promising candidates against the five Leishmania strains tested among the different product evaluated, the Median Inhibitory Concentration (IC 50) varies from 52.49 to 119.6 ìg.mL-1. Besides, this assessment allowed evaluating the cytotoxic effect of essential oil and the petroleum ether extract towards human monocytic cell line THP-1, the result was expressed as the concentration inhibiting cell growth by 50% (CC50), showing respectively a CC50 = 63,4 ìg.mL-1 and a CC50 value higher than 250 ìg.mL-1. The chemical profile of these active extractables has never been described in the scientific literature, their analysis by gas chromatography coupled with mass spectrometry (GC / MS) performed during this study led to identifying 68.77 % of the essential oil total composition and 64.79% of the petroleum ether crude extract’s analyzed fraction. Moreover, the antioxidant properties of the extractable products was assayed via the 2, 2-Diphenyl-1-picrylhydrazyl (DPPH) free radicals scavenging test, the value of IC50 obtained varies from 46.84 to 249.5 ìg.mL-1. In which, the aqueous crude extract exhibited the best antioxidant behavior. Whereas the increase to a maximal essential oil concentration tested of 2000 ìg.mL-1 has not shown any antioxidant effect. However, further studies are required to exploit these preliminary results.