Novel analytical method development for some amide group containing drugs using Bougainvillea spectabilis bract...

To develop and validate a simple, accurate and precise colorimetric method using Bougainvillea spectabilis (B. spectabilis) bract color previously not exploited for estimation of amide group containing drugs i.e. lidocaine and ranolazine in pharmaceutical formulations.

Methanolic extract of B. spectabilis was prepared and evaluated for stability of its color at different pH and temperature for a period of 3 weeks. The accuracy and reliability of the proposed method was ascertained by evaluating various validation parameters like linearity, precision, limit of detection, limit of quantitation and specificity according to International Conference on Harmonization guidelines. About 0.5% of B. spectabilis bract color was added to the working standard solutions of the drugs separately and after formation of color complex, and absorbances were noted at 418 nm.

For color complexes of lidocaine and ranolazine, linearity was found to be in the range of 4 to 24 and 5 to 25 μg/mL respectively. The % relative standard deviation was found to be within specification limits. Presence of lone pair of electron on nitrogen of amide group of both drugs shows basic nature, contributed in formation of color complex between amide and the color pigment obtained from B. spectabilis bracts.

It can be concluded that the method is simple, accurate, economic, and rapid hence can be employed for routine analysis.