Evidence for the spectroscopic determination of artesunate in dosage form

Resistance to conventional antimalarials triggered off new policies to circumvent the devastating consequences of malaria especially in the trans-Saharan Africa. The use of artemisinin-based combinations as first line drug in treatment of uncomplicated malaria was then advocated and adopted by the World Health Organization (WHO). In Nigeria, this new policy has witnessed a surge in the number of circulating brands of such combinations. Unfortunately, at present, there are no "on-the-spot" cheap and reliable assay procedures for artesunate-based combinations. This is what the present research aims to achieve.

Ultraviolet absorption spectroscopy was used to establish the wavelength of maximum absorbance for pure powder of artesunate and then the Beer's plot generated. This was validated and used to assay nine brands (X1-X9) of artesunate in Nigerian drug market.

Distinctive ultraviolet absorption at 287 nm of pure sample of Artesunate in simulated intestinal fluid (SIF) afforded a simple, precise and the most reliable method for the analysis of nine different brands of Artesunate marketed in Nigeria. SIF does not have any appreciable absorption in the ultraviolet region. This simple method yielded a Beer's plot for Artesunate with high correlation (R2) of 0.9972 +/- 0.00016 and was reproducible. The Beer's plot was obeyed in concentration range of 10-200 mg%. The limits of detection (sensitivity) and quantitation were found to be 0.471 mg/ml and 1.27 mg/ml respectively. The results showed that only four out of the nine brands assayed had deviations from label claims that were within acceptable limits.

Based on these convincing data, simple ultraviolet spectroscopy at 287 nm could be used to assay artesunate in formulations.