Electrochemical reduction of the mycotoxin citrinin at bare and modified with multi-walled carbon nanotubes glassy carbon electrodes in a non-aqueous reaction medium

Abstract

O mecanismo de redução eletroquímica de citrinina em acetonitrila mais (C 4 H 9 ) 4 NClO 4 0,1 mol L -1 tanto em eletrodo de carbono vítreo (GC) não modificado quanto em eletrodo GC modificado com nanotubos de carbono de paredes múltiplas foi investigado por voltametria cíclica e eletrólise a potencial controlado. Os resultados obtidos permitiram inferir um mecanismo de eletroredução complexo com etapas químicas e eletroquímicas, acopladas à reação inicial de transferência de elétron. Citrinina apresentou pico catódico único que corresponde no mínimo a duas etapas de redução envolvendo um elétron e duas reações químicas homogêneas, segundo mecanismo de autoprotonação do tipo ECEC (transferência de elétron acoplada com aceitação de próton). As reações químicas se originam nas transferências de próton intermolecular do substrato para os seus produtos intermédios básicos de redução, caracterizando um mecanismo de autoprotonação. Análise cinética por procedimentos de simulação de resultados voltamétricos permitiu uma caracterização completa do mecanismo de redução heterogêneo de citrinina.Electrochemical reduction mechanism of citrinin in acetonitrile plus 0.1 mol L -1 (C 4 H 9 ) 4 NClO 4 at both bare and modified with multi-walled carbon nanotube glassy carbon (GC) electrodes was investigated by cyclic voltammetry and controlled potential electrolysis. Results allowed to infer a complex electroreduction mechanism with chemical and electrochemical steps coupled to the initial electron transfer reaction. Citrinin shows a single cathodic peak that corresponds at least to two electron reduction steps and two homogeneous chemical reactions, conforming to an ECEC (electron-transfer coupled with proton acceptance) self-protonation mechanism. The chemical reactions are originated in the intermolecular proton transfers from the substrate to its basic reduction intermediates, featuring a self-protonation mechanism. Kinetics analysis by simulation procedures of voltammetric results permitted a fully characterization of the mechanism of citrinin heterogeneous reduction.Keywords: citrinin, mycotoxins, multi-walled carbon nanotubes, cyclic voltammetry, square wave voltammetry IntroductionMycotoxins are a group of secondary metabolites produced by fungi of different species and have different structural characteristics. 1 Some mycotoxins are carcinogenic, others are immunosuppressive, vasoactive and others can cause central nervous system damage. Sometimes, the same mycotoxin can cause more than one type of toxic effect. 1 Citrinin or (3R, 4S)-4,6-dihydro-8-hydroxi-3,4,5-trimethyl-6-oxo-3H-2-benzopyran-7-carboxylic acid (CITH, Figure 1) was first isolated from filamentous fungus Penicillium citrinum. 2 It is also produced by other species of Penicillium, 3 Aspergillus 4 and Monascus. 5 Electrochemical Reduction of the Mycotoxin Citrinin at Bare and Modified J. Braz. Chem. Soc. 1132 CITH crystallizes in a disordered structure, with both p-quinone and o-quinone tautomeric forms in a dynamic equilibrium in the solid state (Figur...

Electrochemical Biosensors for the Determination of Toxic Substances Related to Food Safety Developed in South America: Mycotoxins and Herbicides

“…In addition, CIT occurs frequently in foodstuffs, such as cereals, fruits, meat and cheese, and acts synergistically. The presence of OTA, CIT and aflatoxin B1 in rice samples collected from five provinces of the central region in Vietnam has recently been studied using high-performance liquid chromatography (HPLC) with fluorometric detection [72,73]. There is no particular legislation for CIT all over the world to date.…”