BROMOMETRIC EVALUATION OF ARTEMISININ DERIVATIVES IN PHARMACEUTICALS BASED ON REDOX REACTION AND COMPLEX FORMATION
Emmanuel Attih*, Cyril Usifoh, Aniekan Ebong and Victor Anah
ABSTRACT
The widespread distribution of counterfeit artemisinin antimalerials is becoming a serious public health problem in Africa and South-East Asia. Based on this two spectrophotometric methods are developed for the quantification of dihydroartemisinin (DHA) and artesunate (ART). In the methods, excess bromine generated in the solution by the action of acid on bromated-bromide mixture reacts with the drug and the residual bromine in method A reacts oxidatively with fixed amount of methyl orange producing a chromogen that absorbs maximally at 510 nm. In method B the residual bromine displaces iodine fromm potassium iodide which forms a complex with starch indicator which absorbs maximally at 570 nm. In both methods, the concentrations of the drugs increase proportionally with absorbance obeying Beer’s law in the range of 0.5 – 7.0 and 0.3 – 6.0 in methods A and B, respectively. The correlation coefficient were r =0.9989, 0.9998 and r = 0.9992, 0.9996 for methods A and B, respectively for DHA and ART. The methods were validated as per the currently ICH guidelines. The molar absorptivity were 1.59 x 104, 3,0 x 104 and 2.7 x 104 ,2.6 x 104 L/mol/cm and Sandell sensitivity of 0.018,0.013 and 0.011,0.015μg/cm2 respectively for methods A and B. The limit of detection and limit of qualification were within the range of 0.12, 0.30, 0.36, 0.11 μg/ml and 0.42, 0.35, 0.78, 0.32 μg/ml for both methods, respectively. The methods were evaluated for intra and inter-day accuracy (R.E. %) and precision (RSD %) and found to be ≤ 3.16 % and ≤ 2.15 %, respectively. The methods were successfully used to assay DHA and ART tablets procured locally and the results were statistically compared with official methods. The accuracy and practicability of the methods were ascertained by performing recovery experiment via standard addition method showing no interference from pharmaceutical excipient.
Keywords: dihydroartemisinin (DHA), artesunate (ART), artemisinin antimalerials.
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