Interaction of α- and β-zearalenols with β-cyclodextrins

Abstract

Zearalenone (ZEN) is a mycotoxin produced by Fusarium fungi. ZEN primarily contaminates different cereals, and exerts a strong xenoestrogenic effect in animals and humans. ZEN is a fluorescent mycotoxin, although molecular interactions and microenvironmental changes significantly modify its spectral properties. During biotransformation, ZEN is converted into α-zearalenol (α-ZOL) and β-zearalenol (β-ZOL), the toxic metabolites of ZEN, which mimick the effect of estrogen. Cyclodextrins (CDs) are host molecules, and have been studied extensively; they can form stable complexes with several mycotoxins, including ZEN. However, information is limited regarding the interactions of CDs with ZOLs. Therefore, we studied the interactions of α- and β-ZOLs with native and six chemically modified β-CDs by fluorescence spectroscopy. Fluorescence enhancement during complex formation, as well as binding constants, were determined. To understand ZOL-CD interactions better, molecular modeling studies were also carried out. Both mycotoxin derivatives formed the most stable complexes with methylated and sulfobutylated CD-derivatives; however, the CD complexes of α-ZOL were significantly stronger than those of β-ZOL. The data presented here indicate which of the chemically modified β-CDs appear more suitable as fluorescence enhancers or as potential mycotoxin binders.

Removal of Zearalenone and Zearalenols from Aqueous Solutions Using Insoluble Beta-Cyclodextrin Bead Polymer

“…The pH-dependence of mycotoxin removal is in agreement with our previous observations that CDs bind the non-ionized form of ZEN and ZELs with a much higher affinity than the ionized mycotoxins [ 25 , 27 ]. ZEN and ZELs are weak phenolic acids, therefore, their non-ionized forms are dominant at acidic and neutral pH, while alkaline conditions (e.g., sodium borate buffer, pH 10.0) favor the deprotonation of ZEN and ZELs, resulting in their poor interaction with β-CDs [ 25 , 27 ] and decreased the binding of ZEN and ZELs to BBP.…”

“…Since CDs can form (usually low-affinity) complexes with numerous compounds, the suitability of BBP to bind ZEN in beverages was questionable. However, the high stability of ZEN-β-CD and ZEL-β-CD complexes [ 25 , 27 ] may give some selectivity in removing these mycotoxins over other compounds naturally occurring in drinks. As it was demonstrated, BBP caused a significant decrease of polyphenol content and color of corn beer ( Figure 7 ), suggesting the decrease of some beer constituents during mycotoxin removal.…”

“…Despite the stability of the ochratoxin A-β-CD complex being approximately 65-fold lower than the ZEN-β-CD complex [ 24 , 25 ], Appell and Jackson demonstrated that the β-cyclodextrin-polyurethane polymer could significantly decrease the ochratoxin-content of aqueous solutions and red wine [ 29 ]. Patulin was also successfully extracted from apple juice by the β-cyclodextrin-polyurethane polymer for analytical purposes [ 27 ]. Besides these studies, our results further support the hypothesis that CD technology may be used for mycotoxin extraction from different drinks.…”

“…After injecting 20 μL samples, the isocratic elution was performed at room temperature with a 1 mL/min flow rate. Since the examined mycotoxins are fluorescent molecules [ 27 , 32 ], ZEN and ZELs were quantified by a fluorescent detector (Jasco FP-920; λ ex = 274 nm, λ em = 440 nm). Data were recorded and evaluated using the Millennium Chromatography Manager (Waters, Milford, MA, USA), which also controlled the HPLC pump.…”

“…For example, whereas the binding constants ( K ) of aflatoxin B1-β-CD ( K = 400 L/mol), citrinin-β-CD ( K = 220 L/mol), and ochratoxin A-β-CD ( K = 150 L/mol) complexes are relatively low, the stability of ZEN–β-CD complex ( K = 10,000 L/mol) is more than 20 times higher [ 22 , 23 , 24 , 25 ]. Similarly to ZEN, its reduced metabolites, α- and β-ZEL, also form stable complexes with β-CDs [ 26 , 27 ]. Considering the observations that both patulin [ 28 ] and ochratoxin A [ 29 ] can be successfully extracted from aqueous solutions by β-CD polymers, it is reasonable to hypothesize that ZEN can also be removed from water or beverages through the efficient complexation of ZEN with CDs.…”