All onions have components that prevent fungal growth.
There are hundreds of species of onions indigenous to North America. All onions can inhibit the growth of fungi by producing several proteins that interfere with the fungal growth cycle. Several of these proteins have been recently identified and their actions are beginning to be understood.
Allium Sativum Leaf Agglutinin
Garlic, also known as Allium sativum, is a species included in the onion, or Alliaceae, family. A protein, A. sativum leaf agglutinin, or ASAL, had previously been identified as a natural insect repellent. An article in the April 2011 issue of "PLoS One" investigated possible antifungal properties of this molecule. The researchers found that by genetically manipulating ASAL, thereby inducing an additional twist to the protein, the molecule took on antifungal activities. The study concluded that genetic modification of garlic can protect the plant from fungal infection.
Fistulosin
Fistulosin is an antifungal protein, isolated from the roots of the Welsh onion, that was identified in the September 1999 issue of "Phytochemistry." The authors tested this molecule for antifungal properties against Fusarium oxysporum, which can cause fungal infections in humans, insects and plants. The study concluded that fistulosin is an effective antifungal that inhibits the production of fungal proteins.
Ace-AMP1
Tomato early-blight disease is caused by the fungus Alternaria solani and is characterized by the rotting of tomatoes on the vine and potatoes underground. A study in the May 2011 issue of "Applied Microbiology and Biotechnology" investigated the effects of Ace-AMP1, an antifungal protein, isolated from the common onion, Allium cepa. Researchers genetically modified a tomato plant by adding the onion protein and found that the antifungal characteristics were passed on to the tomato. This prevented infection by several species of fungi.
Zwiebelane
A protein called zwiebelane A naturally occurs in the common onion and enhances the antifungal properties of the plant. An article in the November 2010 issue of "Planta Medica" tested the ability of the protein to enhance the antifungal character of polymyxin A, also fond in onions. The study found that zwiebelane A with polymyxin A was effective for killing cells of Saccharomyces cerevisiae, commonly known as baker's yeast.
Tags: antifungal properties, found that, 2011 issue, antifungal protein, antifungal protein isolated
