Banana condensed tannins scavenge glyphosate in aqueous solution through non-covalent interactions

Abstract

The protective effects of polyphenols against glyphosate-induced toxicity in animals are generally considered to be associated with their antioxidant properties. Recently, some researchers put forward that the direct interactions of polyphenols with molecules may also play roles in their biological activities. However, there is little information about the direct interactions between polyphenols and glyphosate. Bananas are demonstrated to be rich in phenolic compounds (especially condensed tannins) at the unripe stage. To provide a possible new mechanism of protection by polyphenols against glyphosate intoxication, the direct interaction of banana condensed tannins (BCT) with glyphosate was characterized by different techniques for the first time. Our results showed that glyphosate could be effectively precipitated by BCT in aqueous solution, and the glyphosate scavenging ability of BCT (10.30–59.14%) significantly increased with the rising condensed tannin concentration (0.25–1.0 mg proanthocyanidin B2 equivalent/mL). Notably, the glyphosate scavenging ability of BCT was closely related to the electrostatic interactions, hydrogen-bond interactions and hydrophobic interactions between BCT and glyphosate. In addition, the interaction of glyphosate with BCT was further confirmed by characterizing the BCT-glyphosate coprecipitates using spectroscopic methods and morphological analysis. Therefore, the precipitation of glyphosate by BCT might reduce the toxicity of glyphosate through affecting its gastrointestinal absorption.