Profiling study of the major and minor components of kaffir lime oil (Citrus hystrix DC.) in the fractional distillation process

Introduction Essential oil is consisting of complex component. It is divided into major and minor component. Therefore, this study aims to examine the distribution of major and minor components on Kaffir lime oil by using fractional distillation. Fractional distillation and distributional analysis of components within fractions have been performed on kaffir lime oil (Citrus hystrix DC.). Methods Fractional distillation was performed by using PiloDist 104-VTU, column length of 2 m (number of plate 120), the system pressure was set on 5 and 10 mBar, while the reflux ratio varied on 10/10, 20/10 and 60/10, and the chemical composition analysis was done by using GC-MS. Chemical composition of the distillated lime oil consisted of mix-twigs and leaves that composed of 20 compounds, with five main components β-citronellal (46.40%), L-linalool (13.11%), β-citronellol (11.03%), citronelyl acetate (6.76%) and sabinen (5.91%). Results The optimum conditions for fractional distillation were obtained at 5 mBar pressure with reflux ratio of 10/10. Components of β -citronellal and L-linalool were distributed in the fraction-1 to fraction 9, hydrocarbon monoterpenes components were distributed only on the fraction-1 to fraction 4, while the oxygenated monoterpenes components dominated the fraction-5 to fraction-9. Conclusion The highest level of β-citronellal was 84.86% (fraction-7), L-linalool 20.13% (fraction-5), sabinen 19.83% (fraction-1), and the component level of 4-terpeneol, β-citronellol and sitronelyl acetate respectively 7.16%; 12.27%; 5.22% (fraction-9).


Introduction
Essential oil is a complex composition that consists of tens to hundreds of compounds. Major components that can be identified in the essential oil include oxygenated monoterpenes, hydrocarbons monoterpene, oxygenated sesquiterpenes, sesquiterpene hydrocarbons, carbonylic compounds, phenols, fatty acids and esters [1]. The chemical composition of essential oil is influenced by several factors, including the level and type of plant species, area, season, temperature, humidity, and other abiotic factors [2,3]. In general, the composition of essential oil is known as secondary metabolites and classified as terpenoids and polipropenoid [4].
Currently, it has been proven that there are two distinct and independent biosynthetic routes, that is the isopentenyl diphosphate (IPP) route and allylic isomer dimethylallyl diphosphate (DMAPP) route, which produces the two compound groups in plants [5].
These two biosynthetic routes are known as mevalonate pathway to the terpenoids, while phenylpropanoids derived from shikimate pathway [6,7]. Researchers argue that there is association between the terpenoid formation with enzyme types and enzymatic reaction mechanisms in biosynthetic processes that involves a variety of reactions, such as hydride shift or methyl group, hydration, protonation, cyclization and isomerization. Genetic modification of metabolic pathways provides some promising results to increase the volatile production, therefore, bacteria, yeast and plants are genetically modified for the production of volatile terpenoids derived from shikimic acid. There are several different explanations about the volatile metabolites production by transgenic microorganisms and genetically modified crops [8].
Researchers conclude that this type of approach can be successfully used to generate the level of terpenoids. However, modification of several groups of these compounds is quite difficult because the terpenoids reservoir precursor may not be sufficient for large production of the desired compound [9,10]. Behrendorff examined the culture media to identify the genes and the production of limonene by using Saccharomyces cerevisiae, and use this information to develop a media in limonene biosynthesis process polarity pushed researchers to develop a method to improve the performance capabilities of GC tool for a quick analysis [11].
Citronellal, geraniol and nerol are the functional isomers of monoterpenoid, while citral is the lemonal from a mixture of terpenoid isomers that is known as the double bond isomers.
Citronellal is responsible for the distinctive aroma of lemon, while the geraniol and nerol is the main monoterpenoid alcohol component of rose oil and, palmarosa oil. Isomer is known as geranial or citral A, while the Z-isomer is known as neral or citral B [12]. Z and E configuration difference is caused by the small showed that there are more (-) linalool than (+) limonene, but both are an active antimicrobial, antifungal and antimalarial [13]. The purpose of this study is to examine the distribution of major and minor components on each kaffir lime oil fraction by using fractional distillation, that is performed under reduced pressure and adjusted reflux ratio. was maintained for 10 minutes, then the temperature was increased from 80°C to 300°C with the increase rate of 4°C/minute. Then the chromatogram was formed.

Results
The What is known about this topic  Essential oil is consisting of complex component which is divided into major and minor component.

What this study adds
 This study showed that the optimum conditions for fractional distillation were obtained at 5 mBar pressure with reflux ratio of 10/10;  This study give information that component with highest level are β-citronellal with 84.86%. Figure 1: Total ionic chromatogram (TIC) of kaffir lime oil that was obtained from its twig