Kinetic spectrophotometric determination of flavonoids using alka-line potassium permanganate

Abstract

Two simple and sensitive kinetic methods were developed for the determination of diosmin and hesperidin in bulk and pharmaceutical preparations. The proposed methods are based on kinetic investigation of the oxidation reaction of the drugs with alkaline potassium permanganate at room temperature for a fixed time of 20 min and 15 min for the first and second methods, respectively. In the first method the absorbance of the green colored manganate ion produced by diosmin and hesperidin was measured at 610 nm. Alternatively in the second method, the decrease in the absorbance of permanganate ion after addition of diosmin was measured at 525 nm. Calibration graphs were linear over the concentration range 5.0- 25.0 and 1.0-20.0 ìg/mL for diosmin using the two methods, respectively and 1.10-2.77 ìg/mL for hesperidin, using the first method. The results obtained were compared statistically with those obtained by a reported method and showed no significant differences regarding accuracy and precision. In addition, the activation parameters such as Ea, ï H, ï S and ï G were also evaluated for the reaction and found to be 15.85 KJ mol-1, 40.79 KJmol-1, 25.59 JK-1mol-1 and -7.63 KJmol-1, respectively.