Analysis and bio-analysis of omarigliptin, trelagliptin and alogliptin: Applied to biological samples and degradation kinetic study

Abstract

A simple liquid chromatographic method was developed for the bio-assay of omarigliptin (OMR), trelagliptin (TRE) and alogliptin (ALO) in rat plasma using Hypersil Gold C18 column with UV detection as an economic alternative for the reported LC-MS methods in the literature. Isocratic elution based on simple mobile phase (acetonitrile:phosphate buffer, 50:50, v/v) was applied with UV detection at 240 nm for OMR and at 274 nm for TRE and ALO because of their structure similarity except for one fluorine atom. Liquid-liquid extraction technique was used for plasma sample preparations using diethyl ether as the best extracting solvent according to log-P of the drugs & applying vacuum evaporation before the reconstitution with the mobile phase. The method was validated according to FDA guidelines. The proposed method was applied to biological samples (n = 3) after oral administration to rats. Further applications were completed using the same LC method including assay of TRE and ALO in human plasma and study of stress degradation for OMR in bulk as a stability indicating assay. Factorial design was applied to test the method robustness using Box Behnken design with three factors and one replicate. First order kinetic plot of acid degradation of OMR at 60 °C, 70 °C & 80 °C showed kinetic plots of the natural logarithm (Ln) of OMR remaining percent versus time for each temperature. Arrhenius plot was used in the kinetic study and half-life (t1/2), shelf life (t90), degradation rate constant (K25), Activation energy (Ea) & Arrhenius frequency factor (A) were calculated. A minor comparative study was also applied to show the difference between UPLC, UHPLC & HPLC for the assay of OMR. All of these applications were performed with the minimal possible cost as the major privilege of the presented economic work over the reported expensive LC-MS bio-analytical methods.