Ivica Strelec

Urinary ochratoxin A and ochratoxin alpha in pregnant women

This study determined exposure of pregnant women to ochratoxin A (OTA). Forty samples of first-void urine samples from Croatian women in the third trimester of pregnancy were analyzed for OTA and its major metabolite ochratoxin alpha (OTα). The subjects filled a short food frequency questionnaire (FFQ). Analysis was performed by HPLC-FLD following liquid-liquid extraction. All samples were subjected in parallel to enzymatic treatment (β-glucuronidase/aryl sulfatase) to release OTA and OTα from the conjugates. The median urinary levels of OTA and OTα before treatment were 0.02 (range: nd-1.07) ng/mL and 0.16 (nd-1.86) ng/mL; the concentrations after enzyme hydrolysis were 0.02 (nd-1.11) ng/mL and 1.18 (0.11-7.57) ng/mL. While OTα levels increased significantly following enzymatic treatment, evidence for OTA conjugation was weak. The ratio of urinary OTα medians after and before hydrolysis was 1.5 times higher than previously reported for nonpregnant female subjects, possibly indicating upregulated metabolism and/or elimination of the mycotoxin and metabolites in pregnancy. The mean daily dietary OTA intake calculated from FFQs (1.08±0.57 ng/kg body weight) was well below the provisional tolerable daily intake and the greatest contributors to intake were cereal products, fruit juices, chocolate and coffee.

Croatian produced unifloral honey characterized according to the protein and proline content and enzyme activities

Abstract In honey, the content of proteins, including the enzymes, is relatively low and has a minor nutritive significance. On the other hand, the proteins, including the enzymes, are usually used as honey quality evaluation parameters. This is because protein content and enzyme activities vary regarding the botanical origin of the honey. Since the results of protein content, glucose-oxidase, and acid phosphatase, for honeys produced in Croatia, are not available, four of the most abundant honey types produced in Croatia (black locust, sage, chestnut, and honeydew honey) are characterised according to the protein and proline content and enzyme activities. The characterisation was done to determine specificities and contribute to the characterisation of unifloral honeys. Dark honey types (honeydew and chestnut honey) had a higher proline content, and diastase, invertase, and glucose-oxidase activity than lighter sage and black locust honey. Black locust honey has a naturally low enzyme activity and showed the highest acid phosphatase activity among the analysed honey types, while honeydew honey, otherwise known to possess high proline content and enzyme activity, had a low protein content comparable to black locust honey. Statistically significant correlations were obtained between all analysed parameters, with the exception of acid phosphatase activity.

Antifungal and antiaflatoxigenic activities of coumarinyl thiosemicarbazides against Aspergillus flavus NRRL 3251

Abstract The antifungal and antiaflatoxigenic effects of two series of coumarinyl thiosemicarbazides on Aspergillus flavus NRRL 3251 were studied. Fungi were grown in YES medium for 72 h at 29 °C in the presence of 0, 0.1, 1, and 10 μg mL-1 of coumarinyl thiosemicarbazides: one series with substitution in position 7 and another with substitution in position 4 of the coumarin core. Dry mycelia weight determination was used for antifungal activity estimation, while the aflatoxin B1 content in YES media, determined by the dilute and shoot LC-MS/MS technique, was used for the antiaflatoxigenic effect estimation. Standard biochemical assays were used for oxidative status marker (TBARS, SOD, CAT, and GPX) determination in A. flavus NRRL 3251 mycelia. Results show that 7-substituted-coumarinyl thiosemicarbazides possess a better antifungal and antiaflatoxigenic activity than 4-substituted ones. The most prominent substituted compound was the compound 3, N-(4-chlorophenyl)-2-(2-((4-methyl-2-oxo-2H-chromen-7-yl)oxy)acetyl)hydrazine-1-carbothioamide, which completely inhibited aflatoxin production at the concentration of 10 μg mL-1. Oxidative stress response of A. flavus exposed to the selected compounds points to the modulation of oxidative stress as a possible reason of aflatoxin production inhibition.

Inhibitory effect of coumarin derivatives on apple (cv. Idared) polyphenol oxidase

Inhibitory effect of 32 coumarin derivatives (20 Schiff bases, 5 thiosemicarbazides, 5 thiazolidinones, and their precursors, 7- hydroxy-4-methylcoumarin and 4-methylcoumarin- 7-yl hydrazine carboxylate) on partially purified apple polyphenol oxidase was investigated. Thirteen coumarin derivatives inhibited polyphenol oxidase (5 Schiff bases, 5 thiosemicarbazides, 1 thiazolidinone, 4-methyl- 7-hydroxycoumarin and 4-methylcoumarin-7-yl hydrazine carboxylate), while 19 derivatives showed no effect on enzyme activity. The most effective inhibitors were thiosemicarbazides, with 4-methyl-1-(2-(4-methyl-2-oxo-2H-chromen- 7-yloxy)acetyl) thiosemicarbazide (compound C23) being the most prominent inhibitor (IC50 = 10.45 µM). The importance of thiosemicarbazide moiety as crucial structure element for strong apple PPO inhibition was confirmed by its cyclisation to thiazolidinone bearing the same substituents as corresponding thiosemicarbazide. Capture of the sulphur atom of thiosemicarbazide group within tiazolidinone ring caused significant loss of inhibitory effect against apple PPO.

Fullerol C60(OH)24 nanoparticles modulate aflatoxin B1 biosynthesis in Aspergillus flavus

The water soluble fullerene C60 daughter product - fullerols C60(OH)24 (FNP) possesses a great potential of modifying secondary metabolites biosynthesis. In order to clarify the extent of interaction, the impact of FNP (10, 100 and 1000 ng mL−1) on aflatoxin production and the available precursors of biosynthesis pathway from Aspergillus flavus NRRL 3251 was determined, in both the mycelia and yeast extract sucrose (YES) medium, during a 168-hour growth period at 29 °C in the dark. The FNP of 8 nm in diameter, and with a zeta potential of −33 mV affected mycelial growth at 1000 ng mL−1 while conidia production was slightly affected at 10 ng mL−1. The FNP effect on aflatoxin and it biosynthetic precursors was concentration dependent and alteration of the sterigmatocystin (ST) export from the cell was observed. Most of the monitored aflatoxin precursors, except norsolorinic acid, were detected in both mycelia and YES medium. However, observed precursor concentrations were much higher in mycelia, with exception of ST. The study shows the loss of FNP antioxidative effect after 120 hours of growth, and strong concentration dependent aflatoxigenic effect after that time. Thus, this data is relevant to guide future considerations on FNP-fungal interactions in the environments and on risk assessment.

Potential use of apple polyphenol oxidase for bioremediation of phenolic contaminants

Phenolic compounds, such as catechol, are released into the environment from a variety of industrial sources and they present serious ecosystem burden. This work examined possibility to use partially purified apple polyphenol oxidase (PPO) for bioremediation of phenolic contaminants. In order to optimize process conditions, optimal pH and temperature for PPO activity were determined, while PPO affinity toward various phenols, as well as effect of some salts and organic solvents which can be found in wastewaters, was used to confirm applicability of PPO in wastewater treatment. It was found that partially purified apple PPO shows maximal activity at pH 6.8 and 25 °C, but exhibit more than 85 % of its maximal activity in pH range from 5 to 8, and more than 90 % of activity in temperature range from 10 to 50 °C. PPO showed high affinity for various di-phenols, but lack of affinity toward mono-phenols. Sodium tetraborate decahydrate moderately inhibited PPO activity, while exposure of PPO to the presence of organic solvents ( = 5 %) caused 40 % loss of its activity. Catechol oxidation by PPO performed for just 5 min in a batch reactor at optimal process conditions resulted in 25 % conversion . Based on obtained data, it seems that partially purified apple PPO has reasonable potential in wastewater treatment.

Proximate analysis of cold-press oil cakes after biological treatment with Trametes versicolor and Humicola grisea

In order to increase the current knowledge on cold‐press oil cakes composition, the present study aims to determine the chemical composition of oil cakes from hull‐less pumpkin (Cucurbita pepo L.), flax (Linum usitatissimum L.), and hemp (Canabis sativa L.) before and after the biological treatment with Trametes versicolor and Humicola grisea using fungal‐based solid‐state technology. After 10 days of treatment, the content of ash, total nitrogen, total proteins, and total organic carbon increased in all the three oil cakes, while the content of ether extracts decreased. After treatment, the concentration of soluble carbohydrates decreased in pumpkin and hemp seed oil cakes, whereas it increased in flaxseed oil cake. During treatment with T. versicolor, the content of fructose significantly increased in hull‐less pumpkin seed oil cake. Fiber content decreased in pumpkin and flaxseed oil cakes after treatment with both of the fungi, whereas it increased in flaxseed oil cake.

Correction to: Characterization of Croatian Honeys by Right-Angle Fluorescence Spectroscopy and Chemometrics

The original version of this article unfortunately contained an incorrect version of author’s names and surnames (underlined). The correct names and surnames are: “Ivica Strelec”, “Lidija Brodar”, “Ivana Flanjak”, “Frane Čačić Kenjerić”, “Tihomir Kovač”, “Daniela Čačić Kenjerić”, “Ljiljana Primorac”.

Scientific Report of the 9th International Congress “Flour-Bread ’17”

1 Josip Juraj Strossmayer University of Osijek, Faculty of Food Technology Osijek, Franje Kuhača 20, 31000 Osijek, Croatia 2 Department of Sustainable Crop Production, Università Cattolica del Sacro Cuore, via Emilia Parmense 84, 29122 Piacenza, Italy 3 Institute of Sciences of Food Production (ISPA), Research National Council (CNR), Via Amendola 122/O, 70126, Bari, Italy 4 Biomin Research Center, Technopark 1, 3430 Tulln, Austria 5 Croatian Institute of Public Health, Rockefeller street 7, 10000 Zagreb, Croatia 6 Institute of Field and Vegetable Crops, Maksima Gorkog 30, 21000 Novi Sad, Serbia

Synthesis and biological evaluation of a novel series of 1, 3-dicoumarinyl-5-aryl-2-pyrazolines

In the present paper novel 1, 3, 5-trisubstituted 2-pyrazolines (4a-q) were synthesized via condensation of different substituted 3-cinnamoyl-2-oxo-2H-chromenes (2a-q) with 2-(4-methyl-2-oxo-2H-chromen-7- yloxy)acetohydrazide (3). Chalcones were prepared via Claisen-Schmidt condensation by refluxing 3-acetyl-2-oxo-2H-chromen (1) with corresponding aldehydes in ethanol, in the presence of piperidine. All of these compounds were characterized by means of their IR, 1H NMR and LC/MS/MS spectroscopic data and elemental microanalysis. Chalcones and pyrazolines were screened for their antioxidant and iron chelating activity.