Optimized and Validated Methods for The Evaluation of Artemisinin Derivatives in Pharmaceuticals Using Redox Reactions

Abstract

The manufacture and distribution of counterfeit/fake artemisinin derivatives is assuming a dangerous dimension, putting in jeopardy the efforts to control malaria. Two simple sensitive reproducible methods are developed for the assay of artesunate (ART) and dihydroartemisinin (DHA) in commercial tablets procured from local Pharmacies in Uyo, South – South, Nigeria. The methods, titrimetric and spectrophotometric methods are based on the use of N-Bromosuccinimde (NBS) as the oxidimetric agent. In the titrimetric method the bromine released in the solution displaces iodine from potassium iodide and the liberated iodine is determined iodometrically. The titration method was found to be stoichiometric in the ratio of 1: 2 [Drug: NBS] and quantitative in the range of 1 – 10mg/mL for both ART and DHA. the spectrophotometric method was found to obey Beer’s law in the range of 5 - 60.0?g/ml and 5 – 70 ?g/ml for DHA and ART, respectively. The molar absorptivity and Sandell sensitivity are 4.0 x 103 L/mol/cm, 5.0 x 103 l/mol/cm and 0,071and 0.077 ?g/cm2 for DHA and ART, respectively. The limit of detection and quantification were 0.080, 0.090 and 0.20, 0.18 ?g/ml for DHA and ART, respectively. The inter and intraday precision and accuracy were ? 2.9 in all cases. The proposed method was successfully used to assay commercial ART and DHA tablets procured locally and statistically compared with reference method via student t-test and F-test with the means showing no significant difference. The applicability and accuracy of the proposed method were confirmed by performing recovery studies via standard addition method with result showing excellent recoveries confirming that pharmaceutical excipients had no effect on the method.