Spectroscopic and time-dependent density functional investigation of the role of structure on the acid-base effects of citrinin detection

Authors: Appell, Michael; Evans, Kervin; Compton, David - Dave; Wang, Lijuan; BOSMA, WAYNE - Bradley University

Submitted to: Structural Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2017
Publication Date: 5/11/2018
Citation: Appell, M., Evans, K.O., Compton, D.L., Wang, L.C., Bosma, W.B. 2018. Spectroscopic and time-dependent density functional investigation of the role of structure on the acid-base effects of citrinin detection. Structural Chemistry. 29(3):715-723. https://doi.org/10.1007/s11224-017-1065-1.
DOI: https://doi.org/10.1007/s11224-017-1065-1

Interpretive Summary: Citrinin is a potential liver toxin and carcinogen produced by fungi that occasionally contaminate agricultural commodities, including corn and other grains. Detection of citrinin is important to prevent exposure and remove contaminated commodities from the food supply. Experimental and computational methods were employed to improve the reliability of fluorescence detection methods of citrinin that are frequently applied to monitor citrinin contamination in grains. The chemical properties of citrinin were identified that influence detection. These findings are important to scientists, the food industry, and regulators looking for more accurate and economical methods to detect citrinin contamination.

Technical Abstract: A time dependent density functional (TD-DFT) study was carried out on tautomers and ionic forms of citrinin to gain insight into the role of chemical structure and micellar environments on detection. Steady state fluorescence studies of citrinin in micellar aqueous solutions produced unusual results for ionic surfactants and the neutral Triton X-100 enhanced fluorescence emission. Ground state and time-dependent density functional studies were carried out on five tautomers of citrinin in the neutral, anionic, dianionic, and cationic forms using the B3LYP density functional and the 6-311+G(2df,2p) basis set. The investigation revealed that deprotonation is a major factor governing the shifts in fluorescence excitation maxima. Moreover, the position of the lowest unoccupied molecular orbitals is removed from the fluorophore moiety of citrinin in the dianionic state which is consistent with the diminished fluorescence of the toxin in basic solutions. The ionic characteristics of certain surfactants can influence the structure and intrinsic spectroscopic properties of citrinin.