Yield and Profile of Essential Oil of Kunzea ambigua: Prediction Using Solvent Extraction and Effects of Distillation Time

Abstract

Essential oil extracted from Kunzea ambigua is new fragrant oil that has been shown to exhibit antimicrobial and anti-fungal properties, however only a few plantations exist to provide for controlled cropping and consistency of product. Extraction technology has been optimised to provide for the rapid assessment of germplasm collected from wild populations of Kunzea ambigua. Small-scale solvent extraction methods were developed to efficiently process large numbers of specimens collected from native stands. The datasets were used to predict the yield and quality of steam distilled essential oils. The effects on volatiles extracted from vegetative material, which had been either frozen or dried prior to extraction, was investigated. Recovery of volatiles was significantly higher from frozen samples, relative to oven-dried, and ethanol was a more efficient solvent compared to petroleum ether. The recovery from solvent extraction of K. ambigua leaf material was similar to, or higher than that from distillation, however, the level of terpinen-4-ol yield increased 15-fold during steam distillation. The compositional profiles and fractional volumes of kunzea essential oil collected at different times during steam distillation were established. The highest oil yield was collected between 30 and 60 mins. α-Pinene and 1,8-cineole dominated the essential oil profile in the early stages of distillation, whilst viridiflorol gradually increased with longer distillation time. This study shows that ethanol extraction of frozen/thawed K. ambigua leaf is useful for predicting the essential oil yield, whilst the time of distillation can be manipulated to maximize the relative concentration of targeted bioactive compounds.