Similarity analysis of essential oils and oleoresins of Eucalyptus globulus leaves produced by distinct methods, solvents and operating conditions

Abstract Eucalyptus globulus leaves can be a source of differentiated essential oil and extracted oleoresin products based on the wise choice of extraction methods, solvents and operating conditions. Accordingly, we performed 36 experimental assays combining extraction techniques (Soxhlet, batch solid-liquid extraction — SLE, supercritical fluid extraction, and hydrodistillation), solvents (supercritical CO2, water, dichloromethane, ethanol, methanol, n-hexane, petroleum ether, ethyl acetate and isopropanol) and operating conditions (temperature and particle size). The resulting products were analysed and compared (including with two commercial essential oils) in terms of total extraction yield, η T o t a l , and chemical composition (by FTIR-ATR). Concerning η T o t a l , the results ranged from 0.79 wt.% (n-hexane SLE at 20 °C) to 37.80 wt.% (Soxhlet with methanol). By applying multidimensional scaling (MDS) for the similarity analysis, Soxhlet and batch SLE products were grouped together, but the temperature of extraction strongly influences the composition of products from polar solvents. In turn, the spectra of both commercial and hydrodistillated oils exhibited a great similarity to pure eucalyptol. Finally, supercritical products differed on the composition in relation to all the other samples, evidencing an opportunity for a new niche type of product.