A novel LC-MS/MS method to characterize the antimicrobial lipid glycerol monolaurate in global human milk

Glycerol monolaurate (GML), a monoglyceride found in human milk (HM), has antimicrobial properties against a broad spectrum of bacteria, viruses, and fungi. In this study, an LC-MS/MS method was developed and validated for quantifying GML in HM based on quantification of two distinct isomers, 1-monolaurin and 2-monolaurin. The method validation included assessments of selectivity (no interferences), linearity (r² range of 0.9954- 0.9985 and 96 of 98 individual points having residual <15%), accuracy (average recovery of 96.4% across both isomers and a range of spiked levels), and precision (total GML repeatability 6.6% RSD and intermediate precision 9.7% RSD). This validated method was used to measure the concentration of GML in unpasteurized HM from 60 mothers and compared geographical locations (Cincinnati and Shanghai), lactation time (weeks 2 and 26), and self-reported maternal allergy status (yes or no). Our findings suggest GML concentration in unpasteurized HM is considerably lower than previously reported in a study characterizing pasteurized HM. The data reported here highlights a novel, validated method used to quantify GML in HM and identified no differences in total GML concentrations when comparing HM from different geographical locations, lactation times, and mother's allergy status.