A simple colorimetric assay to evaluate the pharmaceuticals for alpha-tocopherol and its anti-oxidant potential

A new colorimetric method is proposed to determine α-tocopherol and its anti-oxidant activity by monitoring the ability of α-tocopherol to cause quantitative reduction of ferric ions. The method, based on Trinder reaction, includes incubating 1 μmol of ferric chloride in presence of 0 and 15 through 120 μmoles of α-tocopherol followed by detection of the iron (III) with standard mass of salicylic acid, 30 mg. Evaluation is done by monitoring decrease in absorbance at 525 nm and calculating estimated decrease in ferric ion mass as linear function of α tocopherol over the linear test concentration range (r ± s.e. = 0.999 ± 0.001). The regression estimate, b ± s.e, obtained as 5.5 ± 0.1 nmoles iron (III) reduced μg α-tocopherol is closer to and better than the value, 4.64, obtained with standard pharmaceutical assay for α-tocopherol based on ceric reduction. The method has been used to evaluate the effect of saponification in absence and presence of pyrogallol on the recovery of α –tocopherol, and to compare the pharmaceuticals containing α –tocopherol for their relative antioxidant potentials. The work provides an alternative simple, rapid and inexpensive colorimetric method to evaluate the pharmaceuticals for these activities.