Etude phytochimique et activité antioxydante comparatives des trois variétés de <i>Catharanthus roseus</i> (L.) G. Don

Catharanthus roseus (L.) G. Don, est une plante medicinale largement utilisee en traditherapie contre le diabete, l’hypertension, le cancer et les effets du stress oxydatif. Elle existe en trois varietes ("rosea", "alba" et "hybride") selon la couleur des fleurs. L’etude actuelle porte sur le criblage phytochimique et l’activite antioxydante in vitro (DPPH et FRAP) de l’extrait hydro-ethanolique des trois varietes. Les tests ont ete effectues sur les extraits des feuilles, fleurs et racines. On a note la presence des alcaloides, phenols, flavonoides, tanins, saponines, sterols, terpenes et quinines. Cependant, l’absence des sucres reducteurs, des flavonoides et des saponines dans les racines ainsi que les quinines dans les feuilles a ete relevee. L'analyse comparative par piegeage du radical DPPH a montre que les extraits des fleurs et racines de l’hybride etaient plus actifs, respectivement de 130,023±3,2 et 131,189±1,8 mg EqQ/g. Une tendance differente a ete observee dans les extraits des feuilles ou la meilleure valeur DPPH de 65,746±2,5 mg EqQ/g est attribuee a "rosea" alors que celle du FRAP de 139,935±2,57 mg EqAA/g provient de "alba". Ces resultats devraient encourager la poursuite des travaux sur l'identification et la caracterisation de nouveaux composes bioactifs selectivement abondant pour une meilleure valorisation de Catharanthus roseus sur le plan de phytomedicaments.Mots cles : Catharanthus roseus, varietes, criblage phytochimique, antioxydant. English Title: Phytochemical study and comparative antioxidant activity of the three varieties of Catharanthus roseus (L.) G. DonCatharanthus roseus (L.) G. Don, is a medicinal plant widely used in the treatment of diabetes, hypertension, cancer, and effects of oxidative stress. C. roseus exists in three varieties ("rosea", "alba" and "hybrid") depending on the colour of the flowers. This study focused on phytochemical screening and in vitro antioxidant activity (DPPH and FRAP) of the hydro-ethanol extract of the three varieties. The tests were carried out on leaves, flowers, and roots extracts. The presence of alkaloids, phenols, flavonoids, tannins, saponins, sterols, terpenes, and quinines were noted. However, the absence of reducing sugars, flavonoids, and saponins in the roots and quinines in the leaves was observed. Comparative analysis of DPPH radical scavenging showed that extracts from the flowers and roots of the hybrid were more active, respectively at 130.023±3.2 and 131.189±1.8 mg EqQ/g. FRAP values of the same samples were 175.166± 9.28 and 121.311±7.8 mg EqAA/g dry matter. For the leaves, the best DPPH value of 65.746±2.5 mg EqQ/g was attributed to "rosea" while the FRAP value of 139.935±2.57 mg EqAA/g was for "alba". These interesting antioxidant activities of the "hybrid" variety may be useful against oxidative stress pathologies. The current study might then promote the continuing identification and characterization of new bioactive compounds for a development of Catharanthus roseus.Keywords: Catharanthus roseus, varieties, phytochemical screening, antioxidant.