Variation of Yield and Chemical Composition of Essential Oil from Cupressus lusitanica Growing in Different Agro-ecological Zones of Rwanda

Abstract

Chemical composition and essential oil contents among essential oil-bearing plants are mostly influenced by different factors including ecological features of habitat. In this study, variation in yield and chemical composition of essential oils (EOs) from the leaves of Cupressus lusitanica Mill. (Cupressaceae) in different regions of Rwanda was investigated. Extraction of essential oils from fresh leaves of C. lusitanica collected in March 2021 and April, 2021 from three different ecological zones of Rwanda, Buberuka highland zone (Burera), Central plateau zone (Huye) and Eastern savannah zone (Kayonza) was realized through steam distillation. The chemical compositions of distilled EOs were analyzed using both Fourier transform infrared (FT-IR) spectroscopy and gas chromatography-mass spectrometry (GC-MS), while their yields were determined by simple calculus. The average yields of the EOs were 0.27 ± 0.02, 0.34 ± 0.02 and 0.39 ± 0.01% (v/w) for Burera, Huye and Kayonza, respectively. Results of FT-IR analysis were confirmed by those of GC-MS analysis, and indicated the presence of different groups of compounds including aliphatic alkanes, carboxylic acids, alkenes, aldehydes, aromatics and ketones in the EOs. GC-MS results revealed that sabinene (20.84%), myrcene (19.63%), α-pinene (10.23%) and δ-3-carene (10.13%) were the dominant chemical constituents for EOs of C. lusitanica from Burera. Umbellulone (24.21%), δ-3-carene (16.76%), sabinene (10.54%) and α-pinene (8.21%) were the main constituents for EOs of C. lusitanica from Huye, while γ-terpinene (18.77%), umbellulone (18.16%), isobornyl acetate (9.972%), and myrcene (7.20%) were the major components of EOs of C. lusitanica from Kayonza. The current results demonstrated an intraspecific variation in content and chemical profile of C. lusitanica EOs from one geographical region to another. The observed variations are mostly due to the interactions of C. lusitanica species with climatic and environmental conditions of ecological habitat. However, it could also be the effects of various biotic factors, as well as maturity of plant and stage of plant growth. Further studies are needed to establish the influence of different geo-climatic and environmental factors on each single major component of C. lusitanica EOs.