Sustainable ultrasound-assisted thyme oil extraction: Harnessing thyme residue for enhanced recovery of bioactive compounds

Abstract

Thyme essential oil (TEO), rich in distinct bioactivities, is extensively used in the food and pharmaceutical industries. This study uniquely integrates green ultrasound-assisted extraction (UAE) of TEO, with sustainable bioactive recovery from thyme residues. Nine ultrasound treatments with varying amplitude (40, 60 and 80 %) and time (20, 40, 60 min) were applied. The extracted TEO was analysed for yield (%), chemical composition (GC-MS), antioxidant, and antimicrobial activity. The treatment A3T1 (80 % amplitude, 20 min) came out to be the most favourable treatment with maximum yield of 1.76 % and 4.21 % for oil and bioactives, respectively. Oil demonstrated strongest antioxidant and antimicrobial activity which was supported by GC-MS profiling. For nanoencapsulation of TEO and bioactives, gum arabic offered better encapsulation characteristics with higher EE (80.13 % and 76.33 %), particle size (310 nm and 284 nm), and zeta potential (-21.1 mV and - 26.4 mV) respectively, confirmed by DSC and FTIR, making it the best option for preserving and enhancing bioactive and thyme oil qualities.

Keywords: Antimicrobial properties; Essential oil; Nanoencapsulation; Residues; Thyme grass; Thymol.