Comparison of pennyroyal oils obtained by supercritical CO2 extraction and hydrodistillation

Abstract

Flowers and leaves of pennyroyal (Mentha pulegium L.) were extracted using supercritical CO2 followed by a two-stage fractional separation technique. Using a flow apparatus with an extraction vessel (1 l) and two separators (0.27 l), the best conditions of extraction (P=100 bar and T=50°C) and of separation (P=80 bar, T=−16°C for the first separator and P=18 bar, T=0°C for the second) were found and used to investigate the effect of different mean particle diameters. The pennyroyal oil obtained under these conditions was compared with that obtained by hydrodistillation. Twenty-one components were identified by GC–MS and quantified by GC. Both the hydrodistillation and supercritical oils of Mentha pulegium L. contain the oxygenated monoterpenes pulegone (∽80%) and menthone (∽9%) as the main components. The aroma of the pennyroyal oil obtained with supercritical CO2 was closer to that of the starting vegetable material than the aroma of the essential oil produced by hydrodistillation. Copyright © 1999 John Wiley & Sons, Ltd.