Composes carbonyles majeurs et indices physico-chimiques des huiles essentielles de deux especes du genre Cymbopogon (Poaceae) du Congo-Brazzaville

Abstract

26www.ijeas.org  Abstract-The hydrodistillation of the dry leaves of Cymbopogon citratus (DC) Stapf and Cymbopogon nardus (L.) Rendle harvested in the southern part of Brazzaville (Makelékelé) yields yellow essential oils with respective yields of 1,54% and 2.34%. These were subjected to physico-chemical analyzes and then characterized by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The physical and chemical properties evaluated were the refractive index and the acid number, the respective values of which are (1.4887 and 0.224) for the essential oil of Cymbopogon citratus and (1.4742 and 0.280) for the essential oil of Cymbopogon nardus chromatographic and spectrometric analyzes revealed that the essential oil of Cymbopogon citratus is predominantly monoterpene (95.87%) with a preponderance of oxygenated monoterpenes occupying a high level of (90.24%). The hydrocarbon monoterpenes represent (5.63%), the hydrocarbon sesquiterpenes occupy a very small proportion of (0.07%). The essential oil of Cymbopogon nardus is rich in monoterpenes (77.85%) with a predominance of oxygenated monoterpenes (75.89%). The hydrocarbon monoterpenes are very low (1.96%). Oxygenated sesquiterpenes constitute (12.39%), while hydrocarbon sesquiterpenes are poorly represented (3.46%). Geranial (51.99%) and nereral (32.94%) two geometric isomers, carbonyl compounds forming citral are the major components of the essential oil of Cymbopogon citratus while citronellal (32.53 %) is the major carbonyl compound of the essential oil of Cymbopogon nardus, followed by geraniol (26.84%) and citronellol (10.98%). Thanks to the low refractive index, presence and important proportions of geranial (51.99%), neral (32.94%) and citronellal (32.53%), these essential oils could constitute a reservoir of exploitation carbonyl compounds required for the agri-food, cosmetic, pharmaceutical, and chemical and perfume industries. Résumé : L'hydrodistillation des feuilles sèches deCymbopogon citratus (DC) Stapf et Cymbopogon nardus (L.) Rendle récoltées dans la partie sud de Brazzaville (Makelékelé) fournit des huiles essentielles de couleur jaune avec des rendements respectifs s'élevant à 1,54% et 2,34%. Celles-ci ont été soumises aux analyses physico-chimiques puis caractérisées Composés carbonylés majeurs et indices physico-chimiques des huiles essentielles de deux espèces du genre Cymbopogon (Poaceae) du Congo-Brazzaville 27 www.ijeas.org Composés carbonylés majeurs et indices physico-chimiques des huiles essentielles de deux espèces du genre Cymbopogon (Poaceae) du Congo-Brazzaville 33 www.ijeas.org