Effects of Two Citric By-Products, Hesperidin and Quercetin, on Growth, Aflatoxins Production and Ultrastructure Alterations of Aspergillus parasiticus

PAULA SOL POK; ALZAMORA STELLA MARIS; SILVIA LILIANA RESNIK

Congreso; 2018 IFT Annual Meeting; 2018

Institute of Food Technology, USA

Introduction:Aspergillus parasiticus is a filamentous fungus that can produce aflatoxins (AFs) in maize and other commodities, causing consumers health deterioration and worldwide economic losses. Some flavonoids obtained at low cost from the residues of citric industry have been proved to inhibit the production of AFs from A. flavus.This study investigated the effect of a flavanone, hesperidin (HES), and a flavonol, quercetin (QUER), on the growth, AFs biosynthesis and ultrastructure modifications of A. parasiticus. Method:Aspergillus parasiticus CIM 30456 was identified by sequencing β-tubulin and calmodulin gene fragments. The strain is held in the BAFC Culture Collection. The studies were carried out in Petri dishes, containing 10 g of Malt Extract Agar (MEA) and 0.25 mM of HES or QUER. Each dish was inoculated with 10 μl of A. parasiticus conidia suspension and incubated at 25°C, 14 days, in which colony diameter was recorded using ImageJ software, in order to assess growth parameters. The same flavonoid concentrations were tested against AFs accumulation in 25 g of sterilized maize grains, inoculated with 25 μl of A. parasiticus conidia suspension. After 14 days at 25ºC, AFs were quantified using ?Method 990.33? (AOAC, 2012). Samples (conidia and hypha) for ultrastructure study by transmission electronic microscopy (TEM) were prepared according to conventional techniques.Results:No significant differences were found when A. parasiticus growth rate in presence of the flavonoids was compared respect to control. Nevertheless, regarding AFs production, 0.25 mM HES reduced 74% AFs accumulation on maize and with 0.25 mM QUER, AFs reduction reached 56%.TEM observations allowed explaining AFs production results. QUER induced minor changes in the fungus structure (agglutination and detachment of fibrillar layer, formation of electron dense grains in the inner part of the wall). But HES caused severe morphological alterations (rupture of plasmalemma, retraction of cytoplasm, disappearance of fibrillar layer structure with formation of abundant dense bodies, and dilatation of cell wall).Significance:These results indicated that a flavanone economically obtained from citrus industries discarded fruits and wastes, HES, could be used as an alternative in AFs prevention programmes.Keywords: flavonoids, aflatoxins, Aspergillus parasiticus