Spectrophotometric assay of artesunate using benzaldehydes with electron withdrawing substituents

Abstract

Different analytical methods have been reported for the assay of artesunate. However, these methods require the use of sophisticated and expensive equipment and reagents which are not readily available in many developing countries like Nigeria. This study is aimed at developing a method that is accurate, simple and cost effective using readily available reagents for the assay of artesunate in pure form and in pharmaceutical formulations. The developed spectrophotometric assay method is based on the fact that reactive methylene centre of the acid decomposed product of artesunate readily donates a proton that reacts with benzaldehyde to form a chromogen. This study involves the use of two benzaldehydes with electron withdrawing substituents, 3-bromobenzaldehyde and 4-chlorobenzaldehyde. Both gave immediate yellow coloured products and the wavelength of maximum absorption for the product obtained using 3-bromobenzaldehyde was 452 nm, while it was 456 nm for the product obtained with 4-chlorobenzaldehyde. However, the dissolution of 3-bromobenzaldehyde was incomplete in the acidic medium. The result obtained with 4-chlorobenzaldehyde revealed that Beer’s law was obeyed at the range of 20-100 μg/ml artesunate concentration with a linear coefficient of 0.9996 and the molar absorptivity was 2.1261×10³ mol^-1 cm^-1. The limits of detection and quantification were 1.3832 μg/ml and 4.6109 μg/ml, respectively. The method required water as diluent. The result obtained from recovery studies by standard addition method confirmed that there was no interference from pharmaceutical excipients. The developed method was used to assay five brands of artesunate tablets successfully. The results compared favourably well with those obtained using the method described in the International Pharmacopoeia.

Keywords: Artesunate, Benzaldehydes, spectrophotometry, recovery studies