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

Belline Ndzeli Likibi, Gouollaly Tsiba, Aime Bertrand Madiele Mabika, Arnaud Wilfrid Etou Ossibi, Samuel Nsikabaka, Jean-Maurille Ouamba

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.

https://dx.doi.org/10.31873/IJEAS.6.10.01