Spectrophotometric method to the determination of ascorbic acid in M. stenopetala leaves through catalytic titration with hexavalent chromium and its validation

Abstract

ABSTRACT Moringa stenopetala (Ms) is a drought-tolerant fast-growing indigenous tree in Ethiopia. The leaf part of the plant attracted research attention due to multiple nutritional and health benefits. The health benefits were usually attributed to the presence of compounds having antioxidant properties. One of such compounds is ascorbic acid. The aim of this study was to develop a spectrophotometric method to determine the level of ascorbic acid in the edible leaf parts of the plant. In this method, a decrease in the absorbance of Cr(VI) solution as a result of its reaction with AA was used as a basis for the analysis. Mn(II) was used as a catalyst. The described method was validated against HPLC as a standard technique. Factors influencing the reduction of Cr(VI) by AA, including incubation time, solution pH, and background concentration ratio, were optimized. The theoretical detection limit and limit of quantification were calculated to be 0.00154 and 0.0171 mg/ml, respectively. Out of the three different areas of Ms leaf samples studied, fresh Ms leaves from Arba Minch contained highest concentration (2370.001 mg/100 g) of AA, followed by Konso (2330.48 mg/100 g) and Dilla (210.48 mg/100 g), respectively. It was reduced significantly after boiling for 10 min and found to decrease with increasing cooking time. All Ms samples used in this study contained a relatively acceptable range or moderate amount of total AA (200–250 mg/100 g). The results obtained using the current method were in good agreement with that of HPLC methods (237 (UV–Vis) vs 239 (HPLC) and 233 (UV–Vis) vs 237 (HPLC)). The developed method is simple, fast, and can be successfully applied for selective determination of AA in the presence of other interfering species.