Determination of amino acids in black garlic using high-performance liquid chromatography after derivatization with 9-fluorenylmethyloxycarbonyl chloride

Abstract

Purpose: To quantify the amino acids obtained from black garlic (Allium sativum L.) using high-performance liquid chromatography after derivatization with 9-fluorenylmethyloxycarbonyl chloride (FMOC-Cl). Methods: Homogenized black garlic samples were derivatized with 9-fluorenylmethyloxycarbonyl chloride (FMOC-Cl) reagent in borate buffer at 30 °C for 60 min. The black garlic samples were hydrolyzed with 5.0 mL HCl (6 N) and neutralized to pH 5-6 by adding 30 mL NaOH (1 N). Amino acids were measured using high-performance liquid chromatography coupled with a fluorescence detector after hydrolysis and derivatization with FMOC-Cl reagent. Gradient elution mixture consisted of acetonitrile, methanol, and water at a flow rate of 1.0 mL/min, 0.2 % ammonium acetate, and 0.1 % formic acid. Results: The ranges of the limits of detection and quantification were 30 and 100 g/mL, respectively. The overall intra- and inter-day variations (%RSD) for the precision findings were smaller than 3.43 and 4.63 %, respectively. The accuracy of the developed method was good, ranging from 90.9 to 106.8 %. The amino acids of six black garlic products from the market were determined using the suggested approach. The findings indicated that glutamic acid, the main amino acid, is present in the maximum concentration (564.64-1333.9 mg/100 g) in black garlic. Conclusion: The validated method is for the determination of the amino acids in black garlic and would be a helpful tool for the quality control of products containing black garlic.