Sulphoraphane protected eye cells from damage caused by UV light, which can lead to the increasingly common condition macular degeneration, reported the researchers in the 13 July issue of the Proceedings of the National Academy of Sciences (vol 101, no 28, pp 10446-10451).
Epithelial cells in the eyes are very sensitive to damage caused by the oxidants generated by light exposure. The eye has a number of antioxidant functions to reduce damage to the retina, but as people age, the eye becomes less efficient at removing oxidants. This is believed to be a major cause of age-related macular degeneration, the leading cause of blindness among the elderly. It affects an estimated 30 million people worldwide but this number is expected to double by 2030.
Professor Paul Talalay and Xiangqun Gao at the Laboratory for Molecular Pharmacology at Johns Hopkins Medical School divided human adult retinal pigment epithelial cells into two groups, treating one with sulphoraphane for a 24-hour period. The other acted as a control.
Exposing the cells to UV light afterwards, survival in the sulphoraphane group was much higher, Dr Gao told NutraIngredients, and this protection was dose-dependent, increasing with the amount of sulforaphane provided.
The researchers have yet to demonstrate the same effect in people, proceeding first with a study on mice. And they are a long way from making any inroads into the eye health market, an area with typically low consumer awareness of the association between diet and eye health.
However Dr Gao noted that sulphoraphane could have significant benefits over the category leader, lutein. The reasons have much to do with the mechanism behind sulphoraphane's action in the body.
Sulphoraphane glucosinolate (SGS) plays a role in boosting the body's natural Phase 2 enzyme antioxidant defense systems and functions as a powerful indirect antioxidant detoxifying carcinogens before they can damage cells. Typical direct antioxidant molecules, such as vitamins C and E, scavenge one free radical or other oxidant molecule at a time. Once a direct antioxidant molecule binds to a free radical molecule, rendering it harmless, the antioxidant is consumed and is no longer active.
"Antioxidants react with free radicals directly and once they have reacted, they have to be regenerated. But sulphoraphane does not work directly on free radicals. Instead, it up-regulates or boosts the defence system, letting the body itself fight free radicals."
This mechanism has two advantages, according to Dr Gao.
"It means that the compound not only protects eyes but also every part of the body. It also lasts longer in the body, for between four to five days in the cells," he said.
More than 125 scientific papers have been published on sulphoraphane, broccoli and broccoli sprouts, with many of them focusing on sulphoraphane's anti-cancer activity. It also appears to kill bacteria in the stomach that leads to ulcers and stomach cancer.
In a recent study, Dr Bernhard Juurlink at the University of Saskatchewan showed that feeding broccoli sprouts to rats prevented high blood pressure, heart disease and stroke.
Broccoli sprouts, three-day-old broccoli plants, have been found to provide 20 times the concentration of sulphoraphane glucosinolate as found in adult broccoli. Broccoli sprouts are being marketed by a company set up by the John Hopkins team in Baltimore, called Brassica Protection Products, which offers patented concentrated forms of the sprouts.
They are sold in the US, Japan and New Zealand as a vegetable, and the company is looking for partners for use of the ingredient in other applications.