Hydro-alcoholic extraction kinetics of phenolics from oregano: Optimization of the extraction parameters

Abstract

A kinetic study of the phenolic compounds extraction from the solid residue remaining after the hydro-distillation of oregano (Origanum vulgare ssp. hirtum) was performed. Ethanol-in-water mixtures were used for the extraction and the effect of ethanol concentration, solid particle size, solid-to-liquid ratio, and temperature was examined. The experimental data were adequately fitted by both Peleg’s model and Fick’s law considering two stages of extraction, a high-rate initial one (up to 30 min), followed by a slower stage. The higher rate of phenolic compounds extraction was obtained with 60%, v/v ethanol. Increase in temperature from 22 °C to 60 °C, decrease in particle size (from >1000 μm to <315 μm), and decrease in the solid-to-liquid ratio from 1:20 to 1:40 g/mL resulted in an increase of the initial rate.The HPLC analysis indicated mainly the presence of rosmarinic acid, lithospermic acid, flavonoid glycosides and carvacrol. The 60% ethanol as solvent exhibited the highest phenolics recovery and the strongest antiradical capacity. Increase in temperature from 22 °C to 60 °C led to improvement of both time and efficiency of the extraction performed with pure ethanol.