Microwave-assisted Extraction of Glucosinolates from Eruca sativa Seeds and Soil: Comparison with Existing Methods

Introduction - Glucosinolates (GSLs) are secondary plant metabolites that are abundant in brassicas and their hydrolysis products, isothiocyanates, are toxic to soil pathogens. Efficiency and extraction time are critical for routine analysis of GSLs in plant tissues. Robust analytical procedures are required for the extraction of GSL from soil. Objective - Development and optimisation of a microwave-assisted extraction (MAE) method for the recovery of GSL from plant tissues and soil and comparison of its efficiency with other established extraction methods. Methodology - Solvents, temperature, microwave power and extraction time were examined as parameters controlling MAE efficiency. In rocket seeds the efficiency of MAE was determined through recovery of GSLs from seeds and of sinigrin (1) that was used as internal standard. MAE was then compared with the certified ISO-9167 method and an ultrasonic-assisted extraction (UAE). MAE was also applied for the extraction of GSLs from soils fortified with 1 at three fortification levels. The efficiency of MAE was compared with a recently proposed agitation-filtration (AGIT) extraction method. Results - The optimum conditions identified for extraction of GSLs from seeds were: methanol extraction at 250 W and 80 degrees C for 10 min. MAE and ISO methods showed comparable efficiencies and higher than UAE. In soil, both methods resulted in nearly 100% recovery of I at all fortification levels, although MAE achieved this recovery after a single extraction step compared with AGIT, which required two. Conclusions - The MAE developed is a simple and rapid method for the extraction of GSLs from plant tissues and soil that can be applied to a large number of samples, thus reducing the time of analysis. Copyright (C) 2009 John Wiley & Sons, Ltd.