Chemical Composition of Distilled Essential Oils and Hydrosols of Four Senegalese Citrus and Enantiomeric Characterization of Chiral Compounds

Abstract

Peels of four local Citrus species (Citrus sinensis L. Obsbeck, Citrus reticulata Blanco, Citrus maxima Burm. and Citrus aurantifolia christm.) grown in a same locality under the same climatic conditions were subjected to steam distillation. The essential oils and floral waters obtained were analyzed by gas chromatography coupled with a flame ionization detector (CPG-FID) and by gas chromatography coupled to a mass spectrometer (CPG-MS). The essential oils yields were ranged between 0.2 and 0.7 %. The qualitative and quantitative analyses show 74 compounds in all oils samples. The oils were largely dominated by hydrocarbon monoterpenes with limonene as major compound (91.5-94.0 %; 90.4-93.4 %; 77.7-93.7 % and 34.8-51.2 %) in oils from Citrus sinensis, Citrus reticulata, Citrus maxima and Citrus aurantifolia, respectively. In addition to limonene, oils of Citrus aurantifolia contained high amounts of β-pinene (6.8-14.4 %), p-cymene (5.8-12.2 %), γ-terpinene (0.3 -7.4 %), neral (1.5-9.4 %), geraniol (1.9-12.7 %). Although presenting the same major compound (limonene), the oils had compositions that were qualitatively and quantitatively different. The enantiomeric analyses showed that the chiral major compounds were (R) - (+) - limonene, (S) - (-) – limonene, (1S) - (-) -β-pinene, (1R)-(+)-β-pinene and (S) - (+) - carvone. The hydrosols analyzed were composed of oxygenated compounds and did not have the same major compound. A qualitative and quantitative difference in chemical composition was noted between the Hydrosols.