Novosibirsk Scientists Develop Method to Detect Poisonous Cotton Seed Substance

A team of scientists from Novosibirsk State University and the A.V. Nikolaev Institute of Inorganic Chemistry SB RAS developed a highly sensitive method using luminescence to identify gossypol, a poisonous substance from cotton seeds. The researchers synthesized a new metal-organic framework (MOF) based on terbium, that changes its glow when interacting with gossypol. This research demonstrates that the test system has high sensitivity and selectivity. The results of the research, supported by a grant from the Russian Science Foundation (RSF), are published in the Journal of Hazardous Materials (Q1). 

Gossypol is a toxic substance found in the roots and kernels of cottonseeds. It protects the plant from pests and adverse environmental conditions, such as exposure to ultraviolet radiation. Despite a number of useful properties, in large quantities gossypol is extremely toxic to humans. Poisoning from this toxin causes hemorrhages, loss of appetite, and affects male and female fertility. 

Gossypol enters the human body in various ways. The use of cotton-based feeds leads to the accumulation of phytotoxicant in fish, meat, and dairy products. Unrefined cottonseed oil contains impurities of this toxic substance and can also be hazardous to health. The World Health Organization has set a minimum acceptable level for gossypol in food or feed at 450 parts per million. This is an extremely low concentration, literally hundredths of a percent, so the development of highly sensitive methods to identify this substance in water, cottonseed oil, and human blood plasma is an important challenge. 

The method proposed by Novosibirsk scientists involves the use of terbium-based metal-organic coordination polymers. Terbium belongs to the family of lanthanides metals,  compounds that are capable of luminescence, that glow in response to irradiation. In the composition of the polymer, terbium ions are connected by organic bridges. This makes it possible to fix this glow and increase its intensity. When interacting with the polymer, gossypol absorbs some of the energy necessary to glow and it disappears. Thus, it is possible to simply and quickly fix the presence of a toxicant in a sample and determine its concentration by changing the intensity of the glow. 

This system was tested in experiments. Reactions with the addition of a phytotoxicant at various concentrations were carried out primarily in water. The system was able to detect gossypol at a concentration of 0.76 nM. This is the best sensitivity of all metal-organic polymer test systems. Previous studies using lanthanide-based polymers detected gossypol at a concentration of 28.6 nM. Further, based on the positive results of previous experiments, the researchers evaluated the practical application of the test system for the analysis of gossypol content in blood plasma. The results of the experiment showed that the accuracy of the system does not decrease even in the presence of amino acids and other plasma components that can affect the sensitivity of the determination. 

The last stage of the experiment was the identification of gossypol in oil. Here, scientists encountered a number of difficulties because oil cannot be mixed with water. A polar organic solvent, alcohol, was needed to evaluate the stability and sensitivity of metal-organic polymers in cottonseed oil. Under the new conditions, the system also demonstrated high sensitivity with gossypol detected at a concentration of 1.89 nM. Therefore, polymers are able to respond to amounts of a phytotoxicant that are an order of magnitude lower than the maximum allowable values in food products - 0.86 μM. During the comparative experiment, researchers found that the content of gossypol is highest in untreated cottonseed oil.

The results were summarized by Vladimir Fedin, Project Leader, Doctor of Chemistry, Corresponding Member of the Russian Academy of Sciences, and Head of Inorganic Chemistry at NSU’s Department of Natural Sciences, 

The resulting materials based on terbium have demonstrated a number of promising functional properties. We expect that soon it will be possible to move on to the next stage of development in order to promote our materials on the market. 

Material from the Russian Science Foundation Press Service