A rapid and simplified methodology for the extraction and quantification of allicin in garlic

Abstract

An improved method for quantifying the nutraceutical compound allicin in garlic is presented that optimizes all elements of extraction, including incubation time, sample preparation, extractant, and stability of allicin in extracts under different storage conditions. Maximum allicin concentrations were achieved after only 5 min sample incubation. The highest allicin concentrations were extracted from fresh garlic cloves (12 mg g-1 DW) and reduced with freeze-drying (∼15% reduction) or oven-drying either at 55 °C (∼40% reduction) or 70 °C (∼70% reduction). Of seven extractants evaluated, Milli-Q water gave the highest recovery of allicin compared with methanol (20% and 50%) (93% and 88% recovery, respectively) and phosphate buffer pH 2.5 (93% recovery). Allicin was most stable (∼98%) in extracts in the presence of MeOH (60%) at -20 °C up to 50 days. The low limit of detection (0.09 µg mL-1), limit of quantification (0.3 µg mL-1), and high accuracy (92-95%) validated the optimized method. An assessment of the method across eight garlic varieties showed inherently high genetic differences in allicin concentration (11.4 to 24.1 mg g-1 DW). The presented method is more accurate, convenient, and time-effective compared with previously reported methodologies, but importantly, identifies a clean (water-based) process for the nutraceutical extraction of allicin.