Validation of high performance liquid chromatography methods for determination of bioactive sulfur compounds in garlic bulbs

High performance liquid chromatography (HPLC) methods for determination of organosulfur compounds (OSCs) before their enzymatic decomposition and allicin in garlic were optimized and validated. Four γ-glutamyl peptides, 2 S-alk(en)yl cysteine sulfoxides, and 2 S-alk(en)yl cysteine were simply extracted with water, followed by the sensitive and selective determination of all compounds in a single run using reverse phase HPLC. Allicin was extracted with dichloromethane and diethyl ether and analyzed by normal phase HPLC/UV system. OSCs and allicin were separated on Hypurity Elite C18 and silica gel column, respectively. These methods exhibited excellent linearity for all of the analytes with good correlation coefficient (r>0.984). Average recoveries were in the range of 81.89–102.38% with good standard deviations. The limits of quantitation (LOQs) of OSCs and allicin ranged from 0.76 to 5.79 and 20.09 μg/mL, respectively. The precision results were expressed as relative standard deviation (RSD), ranged from 0.03 to 3.31% for intra-day and from 1.22 to 14.00% for the interday. These analytical methods and validation data may be useful for quality evaluation of garlic bulbs.