Anti-mold activity of copper chelates

Copper in the form of salts is being used for several centuries as disinfecting, anti-fouling, antibacterial, and antifungal agent. The Greeks of the pre-christian era were using copper salts for treating pulmonory diseases and purifying water. It is very common practice in Indian temples and households to use copper vessels to store water for rituals and to drink. Early Phoenicians used to nail copper strips to ship’s hulls to avoid algal deposit and fouling.  Two hundred years back American travelers moving across the continent put silver and copper coins in large wooden water containers to keep water safe for drinking during the voyage.During second world war Japanese soldiers were using pieces of copper in their water bottles to help prevent dysentery.

The research done in the recent past have confirmed the broad spectrum biocidal activities of copper salts and complexes. During early 1980’s work done by Dr.Phyllis J Kuhn indicated metal strips of stainless steel and aluminium supports growth of  Escherichia coli,
Staphylococcus aureus, Streptococcus group D, and Pseudomonas species culture, where as those of copper and brass (having 67% copper) showed little or no growth. This is further confirmed recently by researchers from Arizona University.

As such copper and its salts appear to be safe for human skin and tissues and at the same time extremely toxic to microorganisms. With reference to microorganisms, initial site of action for copper ion is considered to be at the plasma membrane. It has been shown that exposure of fungi to elevated copper concentrations can lead to a rapid decline in membrane integrity. This manifests itself as leakage of mobile cellular solutes like potassium and causes death of cell.

During 1761, the discovery that  weak solution of copper sulfate can effectively  deactivate seed borne fungi led to extensive use of copper compounds in agriculture. The year 1885 saw emergence of Bordeaux mixture which is essentially mixture of copper sulfate and hydrated lime for eliminating downy mildew from grapevine yard. Another modification of the formulation by name Burgundy mixture containing copper sulfate and sodium carbonate, followed soon after. Several thousand tonnes of copper salt mixtures have been used  world over so far, for control of various fungus in agriculture and horticulture. At present these early formulations have been partially replaced by synthetic organic compounds, or by compounds that contain copper in a non-reactive chelated form.This helps to prevent the accumulation of high levels of copper in sediments surrounding the plants.

However, use of copper sulfate for fungal and algal control had complications like toxicity of copper sulfate for aquatic species, incompatibility of copper in ionic forms with other salts leading to inactive copper and with water in presence of sunlight leading to slow formation of corrosive sulfuric acid. The environmental impact over copper build-up in sediments, and the need for increased dosages have resulted in the development of copper-organic complexes that provide the copper in more bio-available and less toxic chelated form.

Molds are filamentous (fuzzy looking) fungi that occur in many feed stuffs including roughage and concentrates. Every year a significant percent of the world’s grain and oil seed supply is spoiled or contaminated by toxins produced by molds. The extent of loss varies from 5% in the developed world to 30 % in sub- tropical and tropical countries, resulting in huge economical loss. Molds are capable of rapid growth in the desirable environment of moisture, stress, relative humidity in storage area, temperature, insest infestation and storage time.  This growth results in nutritional imbalance and the production of mycotoxins, which affects animal productivity and human health through the food chain. The mycotoxins of greatest concern include: aflatoxin, which is generally produced by Aspergillus mold; deoxynivalenol, zearalenone, T-2 Toxin, and fumonisin, which are produced by Fusarium molds and ochratoxin produced by Penicillium molds.One of the chelates which has been found very effective to control molds and prevent toxin prevention is oxine copper. It has been found  to be fungicidal to Aspergillus spp., Fusarium spp. and Penicillium spp. even at very low concentrations. We have also investigated few molecules from nature, which apart from having anti-fungal activity can chelate with copper and hence improve mold inhibition activity many times over. The product under development by us presents synergistic activity from oxine copper and copper chelate of fungicidal molecules from nature.

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