Development of colorimetric method for the assay of artesunate using 4-nitrobenzaldehyde

Purpose: Artesunate is one of the artemisinin derivatives that is commonly used in combination with some anti-malarials as artemisinin-based combination therapies. High performance liquid chromatographic technique is the required standard assay method for artesunate, but this is not readily available or affordable in most developing countries. This study was carried out to develop a simple, accurate and cost-effective assay method for quantitative determination of artesunate. Methods: The method is an indirect colorimetric assay, which was developed from the formation of yellow coloured product due to the reaction between acid decomposed product of artesunate with 4-nitrobenzaldehyde. Results: The wavelength of maximum absorption for the yellow coloured product was 474 nm. The Beer’s law was obeyed at the range of 20-100 µg/ml artesunate concentration with a linear coefficient of 0.9996. The molar absorptivity was 2.3183×103 mol-1 cm-1. The limit of detection and quantification were 0.0753 µg/ml and 0.2283 µg/ml, respectively. The method required water as diluent. The result obtained from recovery study confirmed that there was no interference from pharmaceutical excipients. Five brands of artesunate tablets were assayed using the developed method. Conclusion: The results compared favourably well with those obtained using the official method described in the international pharmacopoeia. The developed method is useful for the quantitative determination of artesunate in tablets and raw pharmaceutical material. Keywords: Artemisinin, quantitative determination, in-direct colorimetric assay, molar absorptivity