Green approaches for the extraction of antioxidants from eucalyptus leaves

Abstract

Leaf extracts of Eucalyptus globulus present a wide range of phenolic compounds with interest in the pharmaceutical, health, agricultural, cosmetic and food industries because of their medicinal properties. Although conventional solvent extraction is the most extensively used methodology to extract and isolate these active compounds, the excessive consumption of time and energy makes its application relatively inefficient. This study investigates other more cost-effective and environmentally friendly techniques for the isolation of antioxidant phenolic compounds, such as enzyme assisted extraction (EAE), microwave assisted extraction (MAE), ultrasound assisted extraction (UAE), and deep eutectic solvent (DES) extraction. First, the conventional extraction was used to evaluate the effect of the particle size and the liquid-to-solid ratio. Next, relevant parameters of the green extraction techniques were optimized, such as time of extraction, enzyme and dose used, microwave power, and type of DES. The optimized extracts from MAE, UAE, DES and conventional extraction were characterized by UHPLC-ESI-MS, showing a similar phenolic profile with 26 tentatively identified compounds. Finally, the conditions leading to the extracts with the highest content in phenolics were evaluated in terms of specific energy consumption. The lowest specific energy consumption was obtained with MAE, with a value more than 13 times lower than conventional extraction.