LC-MS–MS in MRM Mode for Detection and Structural Identification of Synthetic Hypoglycemic Drugs Added Illegally to ‘Natural’ Anti-Diabetic Herbal Products

Abstract

Several products marketed as natural drugs for enhancement of anti-diabetic function have been analyzed and found to contain synthetic hypoglycemic drugs. In the work discussed in this paper, LC-MS analysis ten such drugs [gliquidone (GLQ), glipizide (GLZ), gliclazide (GLC), glibenclamide (GLB), glimepiride (GLM), rosiglitazone (RGL), repaglinide (RPG), metformin (DMBG), phenformin (DBI), and tolbutamide (TOL)] has been improved. Quantification was by use of multiple reaction monitoring mode. The intra-day and inter-day precision of the method ranged from 2.13 to 5.55% and from 3.78 to 8.14%, respectively. LOQ was 1, 1, 1.2, 2, 3, 3, 5, 5, 2, and 1 μg L−1 for GLQ, GLZ, GLC, GLB, GLM, RGL, RPG, DMBG, DBI, and TOL, respectively. The structures of the compounds were identified by collision-induced dissociation mass spectral analysis. The results showed that a variety of synthetic drugs had been illegally added to anti-diabetic herbal products. A surprising result was that some of the adulterants were added into the capsule shell instead of capsule contents. LC-MS–MS is a powerful tool, and the method has wide applicability.