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

Aim: 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. Methodology & results: 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 (R2 > 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. Conclusion: This method was effectively applied for LA and LLys quantification in human urine after oral LA supplementation.