Evaluation of deep eutectic solvents in the extraction of β-caryophyllene from New Zealand Manuka leaves (Leptospermum scoparium)

Abstract

Leptospermum scoparium (Manuka) is a small indigenous shrub belonging to the family of Myrtaceae, which is equivalent to a tea tree (Melaleuca alternifolia) in Australia. Manuka leaves are rich in bioactive terpenes such as β-caryophyllene, which are scientifically proven to have potential activities in different areas including antimicrobial, anti-inflammatory, antitumour, antioxidant, and anaesthetic. This research considers for the first time the application of deep eutectic solvents (DESs) as green and sustainable solvents for the extraction of β-caryophyllene (β-CAR) from New Zealand Manuka leaves. The extraction was carried out using twenty-six types of hydrophilic and hydrophobic DESs. Menthol: Lactic acid DES was found to have higher extractability of β-caryophyllene than n-hexane, methanol, and ethanol as reference solvents. Moreover, Menthol: Lactic acid DES at 1:2 molar ratio was more efficient than conventional steam distillation and Soxhlet extraction. Furthermore, β-caryophyllene showed a good stability in menthol: lactic acid DES over 9 days of storage. The final β-caryophyllene concentration (β-CAR=8.713605mg/g Manuka leaf) after 4 cycles of extraction suggests a good reusability of the potential DES. The extraction of β-caryophyllene using this DES was further optimised using RSM (response surface methodology) combined with BBD (Box–Behnken design). The optimum experimental conditions were as follows: temperature 25.07°C, stirring time 1.09h, and % w/v biomass of 14.99%, which gave an extraction yield of 10.25mg of β-caryophyllene/g Manuka leaf.