Dual-cooled solvent-free microwave extraction of Salvia officinalis L. essential oil and evaluation of its antimicrobial activity

In this study, dual-cooled solvent-free microwave extraction (SFME) using a modified Clevenger-type apparatus was attempted and developed for the extraction of essential oil from S. officinalis. The parameters of dual-cooled SFME were investigated by Box-Behnken design with response surface methodology. Well-fitting model for the dual-cooled SFME was successfully established and verified. The proposed procedure highly accelerated the extraction process and was highlighted with high yield by reducing the heat loss. Moreover, higher amounts of more odoriferous oxygenated monoterpenes and lower amounts of terpene hydrocarbons were present in the essential oils extracted by SFME and dual-cooled SFME in comparison with hydrodistillation (HD), and dual-cooled SFME better prevented the thermal reaction. The essential oils obtained showed outstanding activity against Bacilus subtillis and Staphylococcus epidermidis. Accordingly, dual-cooled SFME represents a more effective and excellent alternative for the preparation of plant essential oil, and S. officinalis essential oil was a potential natural source of antimicrobial.