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Camus Kar Man Choy, Iris Frances Forster Benzie, Pauline Cho; Ascorbic Acid Concentration and Total Antioxidant Activity of Human Tear Fluid Measured Using the FRASC Assay. Invest. Ophthalmol. Vis. Sci. 2000;41(11):3293-3298.
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© ARVO (1962-2015); The Authors (2016-present)
purpose. To evaluate a novel method (FRASC) for total ferric reducing
(antioxidant) activity and ascorbic acid concentration applied to human
tears, to investigate the stability of ascorbic acid, and to determine
the antioxidant status of human reflex tears.
methods. Linearity, sensitivity, and precision of FRASC and ascorbic acid loss
during 7 days’ storage were assessed; total antioxidant activity and
ascorbic acid and uric acid concentrations of reflex tears from 47
healthy subjects were measured.
results. FRASC has good precision, linearity, and sensitivity. Ascorbic acid is
stable for at least 7 days at moderately acidic pH (pH 3.6) and low
temperature. Total antioxidant activity and ascorbic acid and uric acid
concentrations (mean ± SD) in reflex tears were 409 ± 162,
23 ± 9.6, and 68 ± 46 μM, respectively. Ascorbic acid and
uric acid constituted around half the total antioxidant activity
measured. There was a significant correlation between uric acid and
total antioxidant activity (r = 0.754; P < 0.0001). Men had significantly (P = 0.0045) higher tear ascorbic acid concentrations than women.
conclusions. FRASC is suitable for measuring total antioxidant activity and ascorbic
acid in human tears. Further clinical study is needed to investigate
the male–female difference seen, to characterize the remaining 50%
antioxidant activity, and to investigate the effects of environmental
conditions, antioxidant supplementation, age, and ocular disease on
tear antioxidant status.
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