A new study led by the Sanford-Burnham Medical Research Institute reports that carnosic acid, found in the herb rosemary, actually promotes eye health.
Led by Dr. Stuart A. Lipton, the team found that carnosic acid protects the retina from degeneration and toxicity in cell culture and in rodent models of light-induced retinal damage. This suggests that carnosic acid may have clinical applications for diseases of the outer-retina. These include age-related macular degeneration, which is the most common eye disease in the US.
The team exposed the growing cells to hydrogen peroxide in order to induce oxidative stress, thought to be a factor contributing to disease progression in eye conditions such as macular degeneration and retinitis pigmentosa. The cells treated with carnosic acid triggered antioxidant enzyme production in the cells, in turn lowering the levels of reactive oxygen and nitrogen species (cell-damaging free radicals and peroxides).
Next, the team tested carnosic acid in an animal model of light-induced damage to photoreceptors, which are the part of the eye that converts light to electrical signals the brain can read, enabling visual perception. Rodents pre-treated with carnosic acid retained a thicker outer nuclear layer in the eye, as opposed to the untreated group. This indicates that the photoreceptors of the treated group were protected. The treated rodents also exhibited better electroretinogram activity, which is a measure of healthy photoreceptor function.