Extraction and composition of volatiles from Zanthoxylum rhesta: Comparison of subcritical CO2 and traditional processes

The dried fruits of Zanthoxylum rhesta DC syn Z. budrungawall syn. Z. limonella (Dennst) are used as condiments and have spice value. While the essential oil is concentrated in the pericarp, the seeds have fatty oil. The extraction of fragrance/flavour components is carried out from the pericarp by subcritical CO2, modified methanol–subcritical CO2, hydrodistillation and traditional solvent extraction processes and the composition of these extracts are compared. The components are identified by GC–MS and the composition is determined by GC–FID. The principal components such as sabinene, terpinen-4-ol, α-terpineol are present in different amounts in the extracts. The traditional solvent extraction processes provide more amounts of waxy components along with the principal components. Though hydrodistillation process provides a wax free essential oil, the yield is low. The extract obtained by the subcritical CO2 method is superior in comparison to traditional processes, but it contains higher percentage of monoterpenes in comparison to oxygenated monoterpenes. On the other hand, extraction of all the desired components is possible through pre-treatment of pericarp by small amounts of methanol. These details are described and discussed.