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New Spectrophotometric Methods for Estimation of Metadoxine in Bulk and Pharmaceutical Formulations Based on Oxidative Coupling and Charge-Transfer Complex Formation Reactions

Aziz Unnisa, B. Hemalatha, Y. Arun and D. Madhavi

Metadoxine (MTD) is a synthetic antioxidant, providing strong antioxidant protection. It is useful in preventing the damage produced in early stages of liver disease as it prevents the redox imbalance of the hepatocytes and TNF- one of the earliest event in hepatic damage. It is used in alcohol intoxication. In hepatic stellate cells, it prevents the collagen synthesis and reduces fibrosis. Three simple and sensitive spectrophotometric methods (Method A, method B and method C) were developed for the estimation of MTD in pharmaceutical formulations. Method A and method B are based on oxidative coupling of MTD with 3-methyl-2-benzothiazolinone hydrazone reagent in the presence of oxidizing agents like Fe (III) and Ce (IV) to form a stable violet coloured chromogen, which can be estimated at 580 nm. Method C is based on the charge-transfer complex formation between metol and MTD to produce a chromophore, which can be measured at 500 nm. Method A and method B obey Beer’s law in the concentration range of 2-10 μg/mL and method C in concentration of 2-12 μg/mL. The common excipients usually present in dosage forms do not interfere with any of the proposed methods. The optical characteristics, regression analysis data and precision of the methods were also calculated. The accuracy of the methods was evaluated by estimating the amount of MTD in previously analyzed samples to which known amounts of MTD was spiked. The accuracy of the methods was also confirmed by comparison of the results obtained by proposed and reference methods. The methods were validated for use in routine quality control of MTD in pharmaceutical formulations.