Kinetics of ultrasonic extraction of extractive substances from garden (Salvia officinalis L.) and glutinous (Salvia glutinosa L.) sage

The kinetics of ultrasonic extraction of extractive substances (ES) from dry herbs of garden (Salvia officinalis L.) and glutinous (Salvia glutinosa L.) sage using petroleum ether, 70% ethanol or water at 40 °C, as well as the composition of dry extracts, were studied. The mechanism of ultrasonic extraction is confirmed to occur in two steps: first, dissolution of the ES near the particle surface (washing) and, second, diffusion from the solid particles to the bulk of the liquid extract (slow extraction). The process is described mathematically using three concepts of the unsteady diffusion through plant material, the film theory and the empirical equation of Ponomaryov. The yield of ES increases with increasing solvent polarity, and nearly the maximum concentration of ES in liquid extracts is achieved for about 20 min. The composition of extracts depends on both the extraction conditions applied and the plant material.