The first method for determination of lipoyllysine in human urine after oral lipoic acid supplementation.

The first method on urinary excreted amounts of lipoyllysine (LLys) after lipoic acid (LA) supplementation was developed and validated. The suggested procedure allowed simultaneous determination of LLys and LA. After the conversion of analytes into their reduced forms with tris(2-carboxyethyl)phosphine and derivatization via thiol group with 1-benzyl-2-chloropyridinium bromide, separation of analytes derivatives was performed on C18 column using a gradient mobile phase consisting of acetic acid and acetonitrile. The calibration curves for LA and LLys were linear (R > 0.999) in the range of 0.4-12 μM concentration and all validation results were acceptable, according to the US FDA bioanalytical method guidelines. This method was effectively applied for LA and LLys quantification in human urine after oral LA supplementation.