Dansyl chloride derivatization coupled with UPLC-MS/MS for absolute quantification of 47 dipeptides and their profile in the foregut of goats

Dipeptides have shown great potential in improving the production performance of livestock such as cattle, sheep and goats. The ruminal fluid, a complex matrix sample, is a good research object to investigate the healthy status of ruminants and to discover the biomarkers. A pre-column derivatization with dansyl chloride method was established for accurate quantification of 47 dipeptides by liquid chromatography (LC) triple quadrupole linear ion traps tandem mass spectrometry. An optimized LC gradient ensured the separation of Dns-dipeptides on Kinetic XB-C 18 column by the MRM mode. The ruminal fluid was treated with acetonitrile, and then directly derivatization with dansyl chloride under the optimized pretreatment conditions. The linear correlation coefficients were all above 0.99 in the linear range, the detection limits and the limits of quantitation of Dns-dipeptides ranged within 0.03–6.06 ng/mL and 0.09–20.0 ng/mL, respectively. The accuracy and precision were both less than 15.0 %. The average recovery rate of most analytes was between 80.0 % and 122.0 %. Most analytes were stable in 4 °C for three days. Twenty-five dipeptides were detected in the ruminal and abomasal fluid samples collected from the goats fed with corn and soybean-based diet (CS) or mulberry silage (MS) by the method developed. Dns-Gly-Pro, Dns-Gly-Val and Dns-Phe-Ala were the most abundant in the ruminal fluid, while concentrations of Dns-Phe-Ala, Dns-H-Tyr-Leu and Dns-Leu-Leu were the greatest in the abomasal fluid. Concentrations of five dipeptides, including Dns-Trp-Glu-OH, Dns-L-Ala-L-Leu, Dns-Leu-Leu, Dns-Tyr-Glu-OH and Dns-Val-Tyr, in the ruminal fluid of MS group were consistently decreased ( P < 0.05). However, Dns-H-Pro-Phe-OH level in the abomasal fluid of MS group was increased ( P < 0.05). The development of this quantitative detection method will greatly facilitate the understanding of the mechanism of dipeptides metabolism and circulation in the gut of livestock. • The LC-ESI-MS/MS method for simultaneous determination of forty-seven kinds of dipeptides in ruminal fluid with pre-column derivation was first reported. • Developed method can be used to determine the dipeptide profile in abomasal fluid.