Catharanthus roseus (L.) G. Don, est une plante médicinale largement utilisée en tradithérapie contre le diabète, l’hypertension, le cancer et les effets du stress oxydatif. Elle existe en trois variétés ("rosea", "alba" et "hybride") selon la couleur des fleurs. L’étude actuelle porte sur le criblage phytochimique et l’activité antioxydante in vitro (DPPH et FRAP) de l’extrait hydro-éthanolique des trois variétés. Les tests ont été effectués sur les extraits des feuilles, fleurs et racines. On a noté la présence des alcaloïdes, phénols, flavonoïdes, tanins, saponines, stérols, terpènes et quinines. Cependant, l’absence des sucres réducteurs, des flavonoïdes et des saponines dans les racines ainsi que les quinines dans les feuilles a été relevée. L'analyse comparative par piégeage du radical DPPH a montré que les extraits des fleurs et racines de l’hybride étaient plus actifs, respectivement de 130,023±3,2 et 131,189±1,8 mg EqQ/g. Une tendance différente a été observée dans les extraits des feuilles où la meilleure valeur DPPH de 65,746±2,5 mg EqQ/g est attribuée à "rosea" alors que celle du FRAP de 139,935±2,57 mg EqAA/g provient de "alba". Ces résultats devraient encourager la poursuite des travaux sur l'identification et la caractérisation de nouveaux composés bioactifs sélectivement abondant pour une meilleure valorisation de Catharanthus roseus sur le plan de phytomédicaments.Mots clés : Catharanthus roseus, variétés, 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.

The use of Chenopodium ambrosioides in some communities in Togo reveals its importance and its medicinal properties. The plant is often infused for medicinal drinks before use. Thus, through a comparative study, this work focused on the identification of the different phytochemical groups and then on the anti-radical capacities of ethanolic and aqueous extracts of aerial parts (leaves and seeds) of Chenopodium ambrosiooides obtained by maceration and infusion. The phytochemical tests, carried out on the various extracts, showed that they contained certain biomolecules such as flavonoids and tannins. Likewise, the presence of terpenoids and terpenes has been detected. However, it is only in aqueous extracts that the alkaloids have been revealed. The determination of the polyphenol content of the extracts revealed that the aqueous infusion contains 25.699 mgGAE/g DE, followed by the aqueous maceration: 24.873 mgGAE/g DE, after the ethanolic infusion: 21.009 mg GAE/g DE and of the ethanolic maceration: 20.625 mg GAE/g DE. The results of the determination of the anti-radical capacity by the DPPH method after calculation of the IC 50 , revealed that the infusion gives respectively in aqueous and ethanolic medium: 25.541 μg/ml and 48.269 μg/ml while the maceration leads to 29.187 μg/ml 50.999 μg/ml respectively. This study showed that each extract reacted with DPPH and the aqueous infusion was the most reactive.

Introduction: Bridelia ferruginea is a plant known for its antidiabetic properties. However, few studies on leaf extracts have induced anti-hyperglycemic activity on normal mice subjected to carbohydrate overload. The current study was designed to assess the effect of the leaf extracts’ fraction on fructose-induced diabetic mice. Methods: The in vitro ferric-reducing antioxidant power (FRAP) assay were carried out and the condensed tannins quantified. The vanillin-HCl method was used to characterize the condensed tannins. The antidiabetic effect on fructose-induced diabetic mice was evaluated for 28 days using a fructose-enriched fat diet approach. Results: The fraction confirmed the antioxidant activity with a reducing power of 800 μg/mL comparable to ascorbic acid at 200 μg/mL. The condensed tannins were estimated at 79.6 ± 3.4 mg catechin equivalent per gram of sample. Significant decreases in blood sugar levels of 6.25% at the 7th day, 11.04% at the 14th day, 12.61% at the 21th day, and 11.35% at the 28th day were obtained in mice treated with the extract dose of 200 mg/kg of body weight, compared to the positive control group. The decreases of 37.11% of triglycerides and 40.16% of total cholesterol were also obtained. Conclusion: The investigated fraction showed notable antidiabetic activity and might be a good candidate in the treatment of diabetes.

Les hétérocycles sont importants, aussi bien dans les domaines biologique, médicinal et thérapeutique (vitamines, hormones, antibiotiques, etc), que dans le secteur industriel et technologique (inhibiteurs de corrosion, colorants, agents stabilisants, pesticides, herbicides. Les chloroformiates ou chlorocarbonates sont les esters dérivés de l’acide chloroformique. La chimie des N-oxydes hétérocycliques (pyridine et N-oxydes) a connu un important développement au cours des dernières années. L’objectif principal du présent travail est l’étude de l’action du métoxycarbonylchloride sur la pyridine et certains de ses dérivés. Après avoir trouvé les conditions optimales, de nouveaux composés à base de pyridine ont été synthétisés. En remplaçant l’ion chlorure par d’autres ions, les produits synthétisés ont été cristallisés avec un bon rendement. La structure des produits a été caractérisée à l’aide de la spectroscopie infra rouge et la résonnance magnétique nucléaire. Spécifiquement, l’influence de la basicité du noyau hétérocyclique sur les enthalpies de formation des sels produits a été étudiée. En conclusion, la réaction chimique de formation est exothermique avec ΔH° < 0 pour tous les sels étudiés. En utilisant les constantes de Hammett sur le noyau de la pyridine, l’étude a monté que ces chaleurs de réaction dépendent de la basicité du noyau hétérocyclique. En perspective on peut envisager une étude de l’influence de la basicité des différents noyaux pyridiniques sur les effets de conjugaison polaire directe sur le groupe azoté dans les sels N-méthoxycarbonyl-(oxy)-pyridiniums.Mots clés: Pyridine N-Oxyde, chloroformiates, synthèse, constante de Hammett.   English Title: Study of the influence of basicity on the enthalpy of reaction of N-methoxycarbonyl- (oxy) -pyridinium salts Heterocycles are important, as well in the biological, medicinal and therapeutic fields (vitamins, hormones, antibiotics, etc.), as in the industrial and technological sector (corrosion inhibitors, dyes, stabilizing agents, pesticides, herbicides). Chloroformates or chlorocarbonates are esters derived from chloroformic acid. The chemistry of heterocyclic N-oxides (pyridine and N-oxides) has experienced significant development in recent years. The main objective of this work is to study the action of metoxycarbonylchloride on pyridine and some of its derivatives. After finding the optimal conditions, new pyridine-based compounds were synthesized. By replacing the chloride ion with other ions, the synthesized products have been crystallized with good yield. Specifically, the influence of the basicity of the heterocyclic nucleus on the enthalpies of salt formation produced has been studied. The enthalpies formation of salt produced have been determined. In conclusion, the chemical reaction of formation is exothermic with ΔH ° < 0 for all the salts studied. Using Hammett's constants on the pyridine nucleus, the study has shown that these reaction heats depend on the basicity of the heterocyclic nucleus. In perspective, we can study the influence of the basicity of the different pyridine rings on the effects of direct polar conjugation on the nitrogen group in the N-methoxycarbonyl- (oxy) -pyridinium salts.Keywords: Pyridine N-Oxide, chloroformates, synthesis, Hammett constant.