Development of an assay for ozone-specific antioxidant capacity.

A method of determining the ozone-specific antioxidant capacity (OZAC) of lavage samples from the respiratory system was developed: Gaseous ozone (O(3)) was produced in cuvettes by irradiation with an ultraviolet lamp; aliquots of sample or of a saline control were then added and sufficient time was allowed for ozonation to reach completion; and an aliquot of indigo trisulfonate (ITS) was added to react with excess O(3). Because each molecule of O(3) rapidly bleaches one molecule of the deeply colored ITS, an OZAC value in concentration units was computed from the difference in light absorbance between the sample and the saline control multiplied by the extinction coefficient of ITS. Experiments in 0-40 micro M antioxidant solutions indicated that the OZAC values of uric acid and ascorbic acid were close to their actual concentrations and were independent of O(3) concentration. On the other hand, the OZAC of reduced glutathione and possibly human nasal lavage were nonlinearly related to antioxidant concentration and were directly related to O(3) concentration.