Simultaneous analysis of antihypertensive drugs and diuretics as adulterants in herbal-based products by ultra-high performance liquid chromatography-electrospray tandem mass spectrometry

Abstract

The world consumption of herbal-based products has increased substantially for the treatment, prevention and cure of certain diseases. However, ineffective control of the available products has been contributing to the marketing of products sold as “natural”, which often contain illegally synthetic drugs as declared or non-declared components. It has been a common practice especially regarding drugs for treating chronic diseases, such as hypertension. In order to investigate herbal-based formulations with the claim of hypotensive activity, we developed an analytical method using ultra-high performance liquid chromatography-electrospray tandem mass spectrometry (UHPLC-ESI-MS/MS) for simultaneous determination of 13 antihypertensive drugs including diuretics, β-blockers, angiotensin II receptor antagonist and angiotensin converting enzyme inhibitors. Separation was accomplished in 6 minutes using a Zorbax® SB-C₁₈ column using methanol and acetic acid 0.1% as the mobile phase. Limits of detection ranged from 0.02 to 2.51 μg L⁻¹ and accuracy from 80.56 to 111.28%. A simple extraction procedure was used in the pretreatment step by dissolving the samples in 100% methanol followed of a 1000-fold dilution in the mobile phase and filtration through a Teflon membrane (0.2 μm). No adulterants were detected in the formulations as non-declared drugs. However, five samples contained the diuretics hydrochlorothiazide and furosemide as declared on the label. Quantification of diuretics in these samples revealed doses above and below the recommended dose for furosemide and hydrochlorothiazide.