Toxicity assessment of 7,8-dihydroxy-4-methylcoumarin and vanillic acid

Phytobiotic feed additives have promising potential in the feeding of farm animals, providing improved health and productivity. These compounds have a variety of effects, including antioxidant, anti-inflammatory, antibacterial, and anti-QS. Thus, phytobiotics may represent a potential tool for the treatment and prevention of infectious diseases of farm animals. However, hepatotoxicity is a significant side effect of some of them, so more detailed studies are needed to safely use these compounds as feed additives, including dose, bioavailability, metabolic interactions, and risks associated with long-term exposure. The purpose of this research was to evaluate the toxicity of two phytobiotic compounds, 7,8-dihydroxy-4-methylcoumarin and vanillic acid, using a recombinant luminescent strain of Escherichia coli K12 MG1655 pXen7 and a representative ciliated protozoon, Stylonychia mytilus. These two test organisms are commonly used to assess the overall toxicity of feeds. The results of the study showed differences in the toxicity levels of the two compounds when tested using both organisms. Vanillic acid exhibited higher toxicity than 7,8-dihydroxy-4-methylcoumarin. For the bacterial biosensor, complete suppression of luminescence was observed at maximum concentrations (0,0125 and 0,125 M). For Stylonychia, instant cell lysis was observed across the entire concentration range after one hour of exposure. In contrast, 7,8-dihydroxy-4-methylcoumarin showed a lower toxic effect, with the toxic effect only manifesting itself at high doses and disappearing with a decrease in concentration. However, after three hours of exposure for Stylonychia mytilus, a toxic effect was still recorded at all remaining experimental sites. These results emphasize the need for careful monitoring of phytobiotic use in animal feed and highlight the importance of further research on these feed additives.

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