A novel and sensitive HILIC-CAD method for glucosamine quantification in plasma and its application to a human pharmacokinetic study

The clinical effect of glucosamine, the most widely used supplement in patients with osteoarthritis, on joint pain and function improvement, is reported to be inconsistent. Inter-patient variability in the pharmacokinetics of glucosamine, especially its oral absorption, could contribute to the inconsistent clinical outcomes. To test this hypothesis, a novel but simple Hydrophilic Interaction Liquid Chromatography coupled with Charged Aerosol Detector method was developed and validated. The sample was prepared by simple protein precipitation and analysed using an amino column and acetonitrile:100 mM ammonium formate with gradient elution. The developed method was linear (12.5–800 ng/mL, r² = 0.999) and the relative standard deviations for intra- and inter-day accuracy, precision and repeatability were all less than 6%. The sensitivity of the method (lower limit of quantitation; 12.5 ng/mL) allowed the quantification of endogenous and exogenous glucosamine levels in 12 patients with osteoarthritis, taking 1500 mg glucosamine daily. The analysis showed 120-fold variation (81.7% variance) in exogenous glucosamine levels among the patients, indicating that substantial variability in the extent of absorption and/or rate of elimination could be a possible cause for the reported inconsistent clinical outcomes. The newly-developed method was sensitive and can be used to study the pharmacokinetics of glucosamine.