Chemical characterizations of the aromatic compositions of two citrus species: Citrus Aurantium and Citrus Reticulata

Aromatic plants produce essential oils as secondary metabolites, but their exact role in the processes of plant life remains unknown.1 Some authors believe that the plant uses oil to repel or attract insects, in the latter case, to promote pollination. Others consider the oil as an energetic source, facilitating certain chemical reactions, conserve the humidity of plants in desert climates.2 Some essential oils are used for the defense of plants against herbivores, insects and microorganisms.3


Introduction
Aromatic plants produce essential oils as secondary metabolites, but their exact role in the processes of plant life remains unknown. 1 Some authors believe that the plant uses oil to repel or attract insects, in the latter case, to promote pollination. Others consider the oil as an energetic source, facilitating certain chemical reactions, conserve the humidity of plants in desert climates. 2 Some essential oils are used for the defense of plants against herbivores, insects and microorganisms. 3

Collection of samples
Samples of the aerial part (stems, leaves and flowers) of Citrus Aurantium (CA) and Citrus Reticulata (CR) were harvested from cooperatives in February (2017) respectively in the Beni Mellal regions (Morocco). Species have been verified by a botanist at Forest Research Center, khénifra, Morocco.

Extraction of essential oils from citrus
The essential oils were obtained by hydrodistillation of the aerial parts (stems, leaves and flowers) in fractions of 250 g for a period of 3 h, using a Clevenger type extractor. Water vapor loaded with essential oils condenses in a coolant and is collected in a separatory funnel and dried with anhydrous sodium sulphate (Na 2 SO 4 ) before analysis. The HEs were stored at 4°C for later use in the various analyzes.

Chromatography (GC) coupled Mass Spectrometry (MS)
The analysis of the essential oils was carried out by gas chromatography coupled with mass spectrometry (GC-MS). Coupling was performed on a Hewlett-Packard model 5970 (quadrupole detection system), equipped with a fused silica capillary column of 2mm×0.23mm DB1 type; temperature programming from 50°C to 200°C, with a gradient of 5°C min-1. The retention indices were determined by gas chromatography on two fused silica capillary columns (25m×0.25mm) of the type OV-101 and Cabowax 20M, with temperature programming identical to that used for the coupling.
For Citrus Reticulata the chromatographic analyzes resulted 6 in the identification of 24 compounds, representing (95.41%) of the essential oil, Limonene (67.04%), γ-Terpinene (15.50%) and α-Pinene (2.75%) were the major components. these results did not agree with previous research on the same plant. The chemical constituents of the essential oils of peels and leaves of 15 mandarin species among 41 varieties of Citrus reticulata have been studied. 7,8 Tangerine skin essential oil has been reported to have two main chemotypes, limonene and limonene/ γ-terpinene. Leaf oil showed variations in the components and was distinguished for peel oils with three main chemotypes: sabinene/ linalool, linalool/γ-terpinene and methyl N-methylanthranilate. 8

Conclusion
In the present work, we have characterized the chemical composition of essential oil of two citrus species: Citrus Aurantium and Citrus Reticulata collected at "Beni Mellal" (Morocco). Identification of the chemical constituents was performed based on GC-MS analysis. It can therefore be concluded that the chemical composition or the percentage of the constituents of the essential oils differs according to the part of the plant subjected to the extraction, according to the geographical zones, the period of harvest and the age of the plant.