The efficiency of 2-nitrophenylpyruvic acid as a cathode material in a magnesium/zinc based primary battery is examined. The discharge performance of the cell is investigated under different parametric variations such as temperature, nature of electrolyte, current drain and zeolite modification. A 7e reduction seems to be responsible for the electrochemical reaction causing the reduction of 2-nitrophenylpyruvic acid to an indole intermediate which is oxidatively cleaved to form anthranilic acid as the end-of-discharge product. Participation of oxygen in the reduction process is indicated. The discharge capacity is 1.03 Ah g(-1), the highest value ever observed in organic batteries.