Identification of Sesquiterpenes in Citrus Essential Oils by Cryofocusing GC/FT-IR

Comparative Study of the Chemical Profiles of the Essential Oils of Ripe and Rotten Fruits of Citrus Aurantifolia Swingle

Most often during the processing of lime fruits for essential oil extraction, rotten fruits are used along with ripe ones. In this study, we examine the volatile constituents of the essential oils from both ripe and rotten lime fruits (Citrus aurantifolia Swingle) from Nigeria. The oils were isolated by hydrodistillation and analyzed using GC-MS. The ripe and rotten lime oils contained 55 and 49 components, respectively. Both oils were rich in limonene (21.0%, ripe lime; 21.3% rotten lime), α-terpineol (11.7%, ripe; 14.1%, rotten), terpinene (8.3%, ripe; 8.9% rotten lime), α–terpinolene (2.5%, ripe; 8.5%, rotten) and ( E)-α-farnesene (6.3% ripe lime; 4.8% rotten lime). The other major components, α-pinene (11.1%), and linalool (5.5%) were identified in ripe lime oil only. Limonene and citral, which are believed to be the two major citrus odour contributors, were present in both ripe and rotten lime oils. Aldehydes like decanal and the farnesenes, which are also important in citrus flavor, were represented in both lime oils. Some notable components of ripe lime fruit oil, like trans-β-ocimene, linalool, myrcenol, dodecanal, trans-β–bergamotene and trans-γ–bisabolene, were absent in the rotten fruit oil. It could be suggested that some compounds like cis-ocimene, trans-linalool oxide, p-mentha-3-en-1-ol, mentha-1,4,8-triene, citronellal, trans- β–bergamotene and α–copaene, which were not identified in the ripe fruit oil, were introduced into the lime oil by the incorporation of rotten fruits in the distilled samples.

Volatile compounds from leaf-buds of Populus nigra L (Salicaceae)

Volatile components from fresh and air-dried leaf-buds of Populus nigra L. (Salicaceae) were isolated by Likens-Nickerson apparatus and analyzed using GC/MS. Forty-eight components (ca. 95% of the total isolate) were identified among black poplar bud volatiles. Sesquiterpene alcohols beta-eudesmol and alpha-eudesmol represented 26.3-28.7% of the oil. Other major sesquiterpene compounds were gamma-selinene (7.6-8.8%), delta-cadinene (7.8-8.6%), alpha-elemene (3.3-5.2%) and gamma-cadinene (3.9-4.2%). Hemiterpenes were also identified (2.2-7.6%). Monoterpenes were present in low percentages (1.6-5.7%). Aliphatic and aromatic alcohols, carbonyl compounds and aliphatic acids were identified among non-terpene volatiles (9.8-13.5%). The fresh buds contained 0.27% and dried 0.12% essential oil. Air-drying moderately effected the volatiles qualitative and quantitative composition.