Analysis of Metformin and Five Gliptins in Counterfeit Herbal Products: Designs of Experiment Screening and Optimization.

BACKGROUND: Drug counterfeiting is a rising problem due to difficulties with identifying counterfeit drugs and the lack of regulations and legislation in developing countries. OBJECTIVE: This study aims to develop a robust and economic reversed phase high performance liquid chromatography (LC) method for simultaneously determining metformin HCl, vildagliptin, saxagliptin, alogliptin benzoate, sitagliptin phosphate monohydrate, and linagliptin to target counterfeiting. METHODS: Plackett-Burman (PB) and Box-Behnken (BB) designs were used to screen and optimize the mobile phase composition. Chromatographic separation was carried out on an Inertsil® ODS-3 C18 column with isocratic elution mode and the mobile phase was a mixture of acetonitrile-methanol-ammonium formate buffer, pH 3.5 (25:10:65, v/v/v). This method was applied to analyze synthetic drugs in three traditional Chinese and Indian herbal medicines. To identify the adulterants, thin-layer chromatography (TLC), nuclear magnetic resonance (NMR), and mass spectrometry (MS) were used on counterfeit herbal medicines. RESULTS: The developed method is sensitive, simple, rapid, economical, accurate, and highly robust. Student's t-test and variance ratio (F-test at P < 0.05) were used to compare the results statistically with the reference methods. CONCLUSION: The study found that the analyzed herbal medicines were adulterated with metformin and the quantification of anti-diabetic counterfeits was therefore applied. HIGHLIGHTS: This study determined counterfeited anti-diabetic drugs in Indian and Chinese traditional herbal medicines(THMs). Design-of-experiment, PB, and BB designs were used. Method validation was also performed in accordance with the International Conference on Harmonization guidelines.

Stability-indicating chemometric methods for the determination of pyritinol dihydrochloride.

Three multivariate calibration methods, including classical least square with nonzero intercept (CLS), principal component regression (PCR) and partial least square (PLS), have been used for the determination of pyritinol dihydrochloride in the presence of its degradation product. The CLS, PCR and PLS techniques are useful in spectral analysis because the simultaneous inclusion of many spectral wavelengths instead of the single wavelength used in derivative spectrophotometry has greatly improved the precision and predictive abilities of these multivariate calibrations. A training set was constructed for the mixture and the best model was used for the prediction of the concentration of the selected drug. The proposed procedures were applied successfully in the determination of pyritinol dihydrochloride in laboratory-prepared mixtures and in commercial preparations. Pyritinol dihydrochloride was analysed with mean accuracies 99.99 +/- 0.905, 99.91 +/- 0.966 and 99.92 +/- 0.962 using the CLS, PCR and PLS methods respectively. The validity of the proposed methods was assessed using the standard addition technique. The proposed procedures were found to be rapid and simple and required no preliminary separation. They can therefore be used for the routine analysis of pyritinol dihydrochloride in quality-control laboratories.