Metal-absorbing plants as source of new nutraceuticals

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Related tags: Selenium

Metal-loving plants that store large amounts of micronutrients in
their tissues could be the source of new nutraceuticals.

Too much metal in the soil leads to a contaminated brownfield. Too little metal in the diet causes disease and malnutrition. According to David E. Salt, professor of plant molecular physiology at Purdue University, the solution to both problems may be metal-loving plants that take up large amounts of metal in their tissues. In the past recent years, there has been much scientific interest in using metal hyper-accumulating plants to clean up hazardous materials sites, a process called phytoremediation. However, Dr. Salt considers that metal-accumulating plants may have a broader potential as a way to improve people's diets or even to create foods that fight cancer. "It's just two sides of the same coin,"​ he says. "One of the things about metals that many people don't realise is that a lot of them are essential micronutrients that we need. They play a crucial role in certain enzymes that our bodies use to function."​ Dr. Salt recently announced that he has identified and cloned the genes from a species of these plants that store metals in their tissue. Humans need a variety of metallic micronutrients in their diets, such as iron, copper, manganese and zinc. According to the World Health Organization, the lack of proper micronutrients causes health problems in many underdeveloped nations, particularly in children and pregnant women. "For example, iron and zinc deficiencies have been termed the hidden hunger in the world,"​ Salt says. "Many people suffer disease from the lack of zinc or iron in their diets; they are not just suffering from the lack of food. So we are interested in making foods that are enriched in these essential micronutrients."​ The metal selenium is known to be a potent anti-carcinogen, and there are wild plants that accumulate selenium naturally. If these genes could be moved into crop plants, Dr. Salt says, new foods could be created that have anti-cancer properties. In the Western United States, there is a plant known as locoweed, astragalus bisulcatus​, which accumulates selenium. The plant gets its descriptive name because livestock that eat it can become disoriented and stumble about after ingesting too much selenium. Locoweed hyper-accumulates selenium, and according to Dr. Salt, it may be possible to create functional foods that have cancer-fighting properties from this plant. "Fortuitously, one of the most potent and easily absorbed selenium compounds is the compound that is hyper-accumulated by this plant,"​ Salt says. "So this plant has the very extraordinary ability to make this anticarcinogenic form of selenium."​ Dr. Salt, in collaboration with NuCycle Therapies Inc., has a grant from the National Cancer Institute to clone the gene from locoweed that causes the plant to pull selenium from the soil. Although selenium supplements are available already, according to Dr. Salt most of these are of little use because the human body can only absorb and use selenium if it is in certain chemical forms. "If you go into the health food store right now, you will see that there are many different selenium supplements. Most of those are actually sodium selenide, or sodium selenate, which is a chemical form that our bodies can't use very well. It has been shown to not be very effective,"​ he says. Dr. Salt claims that the first products to market would be dried plant material that is enriched in bioavailable forms of selenium. "In the long term we would probably like to try to engineer a vegetable crop so that we would take the selenium that's in the crops right now and move it into a more anticarcinogenic form in the foods we already eat,"​ he says.

Related topics: Research

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