The Extraction of Essential Oil from Kaffir Lime Peel via Ultrasonic–Assisted Extraction

Abstract

Essential oil from kaffir lime (Citrus hystrix DC.) peel is a high–value natural product widely utilized in the cosmetic and herbal medicine industries. Currently, the extraction of kaffir lime essential oil still relies on traditional methods, such as hydrodistillation and steam distillation. However, traditional extraction methods are typically time-consuming, energy-intensive, and involve high temperatures (³100°C), which may alter or degrade the structure of certain aromatic compounds, such as monoterpenes. In contrast, ultrasound-assisted extraction (UAE) can achieve higher yields in a shorter time while better preserving the chemical composition and natural aroma, as it avoids prolonged exposure to high temperatures. Therefore, this study aims to investigate the chemical composition of essential oil from kaffir lime peel using a green extraction technique via UAE. The chemical constituents and their concentrations are analyzed using gas chromatography–mass spectrometry (GC–MS) by comparison with the NIST Library. The GC–MS analysis demonstrated that UAE efficiently extracted and resolved the major volatile constituents, revealing a highly unique chemotype characterized by two codominant monoterpene hydrocarbons: D–Limonene (22.73%) and β–Phellandrene (21.16%). These were followed by Citronellal (10.07%), α–Pinene (7.15%), α–Terpineol (3.71%), and Terpinen–4–ol (3.17%). Notably, the mild conditions of the UAE process successfully preserved the intact biosynthetic cascade of oxygenated monoterpenes, particularly thermolabile esters, including Isopulegol (2.53%), Citronellyl acetate (2.12%), Citronellyl propionate (2.09%), and Citronellyl butyrate (1.81%). The findings indicate that UAE is a highly efficient, rapid, and sustainable green extraction method capable of preserving the native chemical profile and biosynthetic integrity of kaffir lime peel essential oil. The distinctive chemical profile obtained in this study suggests significant potential for downstream application and value–added product development in the aromatherapy, nutraceutical, and cosmetic sectors, thereby supporting sustainable community–based bio–economies.