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Zohra Fadli, Charles W Scales, Shivkumar Mahadevan; Antioxidant Capacity of a Phenolic Benzotriazole (Norbloc) in Soft Contact Lens Materials: A Benefit Beyond UV Blocking. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1759.
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© ARVO (1962-2015); The Authors (2016-present)
Phenolic benzotriazole-based ultraviolet (UV) absorbers are used in a variety of consumer applications, particularly in polymers, cosmetics and sunscreens. Norbloc (NB), a compound within this class, is used in some contact lenses (CLs) to help protect the eye from the transmission of direct and reflected UV rays. The phenolic structure of this compound suggests an anti-oxidant (AO) benefit in addition to UV absorption. To demonstrate this added benefit, the AO capacity of the UV-active structure within NB was measured and compared to that of known biologically significant AOs.
A hydrolyzed version of NB was obtained and the AO capacity was measured using Oxygen Radical Absorbance Capacity (ORAC), a known method widely used in the food industry. ORAC capacity of NB was compared to that obtained for 10 known AO compounds, i.e. Astaxanthin, Vitamin E, Epigallocatechin Gallate, Alpha Lipoic Acid, Butylated Hydroxytoluene, Glutathione, Gingerol, Ubiquinone, Gallic acid and Trolox.
The ORAC test demonstrated that the NB derivative has a very high AO capacity, with an ORAC score of 4132 ± 620 Trolox Eq./gram. This value is 4 times higher than that for Vitamin E (988 ± 148 Trolox Eq./gram) and significantly higher than several other biologically significant AO compounds, with the exception of Gingerol, which had an ORAC score of 8179 ± 1227 Trolox Eq./gram.
NB, a UV blocker present in certain manufacturers’ CLs is a phenolic benzotriazole derivative that exhibits a high AO capacity, as demonstrated by the ORAC test. The AO capacity was 4 times higher than Vitamin E and significantly higher than other known AO used in this study. This data suggests that there may be an additional benefit of using NB in a CL, beyond UV blocking, i.e. the protection of tear-film components and ocular system from oxidative damage. Additional studies are currently underway to investigate the clinical implications of using NB in CLs materials.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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