Bojan Šarkanj

Synthesis and Antioxidant Activity of Some New Coumarinyl-1,3-Thiazolidine-4-ones

A series of Schiff’s bases (E)-N-2-aryliden-2-(4-methyl-2-oxo-2H-chromen-7-yloxy)acetohydrazides 2a-l and N-(2-(substituted phenyl)-4-oxo-thiazolidin-3-yl)-2-(4-methyl-2-oxo-2H-chromen-7-yloxy)acetamides 3a-l were synthesized and evaluated for their antioxidant activity by the phosphomolybdenum method. Most of the Schiff’s bases and thiazolidine-4-ones bearing two hydroxyl groups on the phenyl ring showed excellent antioxidant activity in comparison with ascorbic acid. Preliminary investigation on cytotoxic and antifungal activity was done on some representative samples.

4-Methyl-7-hydroxycoumarin antifungal and antioxidant activity enhancement by substitution with thiosemicarbazide and thiazolidinone moieties

According to literature data, thiosemicarbazide and thiazolidinone moieties should enhance biological properties of coumarin. Antioxidant, metal-chelating and antifungal activities of all compounds were investigated and compared to the activity of the starting material, 7-hydroxy-4-methylcoumarin, and were proven to possess potent antioxidant and antifungal activity. In general, thiosemicarbazides showed higher scavenging activity towards DPPH and galvinoxyl radicals than did 4-thiazolidinones and some of them had the same or even better activity than had ascorbic acid itself, depending on the free radical used. In antifungal activity tests towards four foodborne mycotoxigenic fungi, Aspergillus flavus, Aspergillus ochraceus. Fusarium graminearum and Fusarium verticillioides, coumarin derivatives were proven to possess a very high activity in terms of growth inhibition, depending on the fungi investigated. In general, 4-thiazolidinones showed better antifungal activity than did thiosemicarbazides. F. graminearum was the most susceptible to the compounds investigated and F. verticillioides was proven to be the most resistant. Two compounds, both coumarinyl thiosemicarbazides, were found to possess both antifungal and antioxidant activity which could be useful for applications in medicine, food industry and agriculture.

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.

Identification of a novel human deoxynivalenol metabolite enhancing proliferation of intestinal and urinary bladder cells

The mycotoxin deoxynivalenol (DON) is an abundant contaminant of cereal based food and a severe issue for global food safety. We report the discovery of DON-3-sulfate as a novel human metabolite and potential new biomarker of DON exposure. The conjugate was detectable in 70% of urine samples obtained from pregnant women in Croatia. For the measurement of urinary metabolites, a highly sensitive and selective LC-MS/MS method was developed and validated. The method was also used to investigate samples from a duplicate diet survey for studying the toxicokinetics of DON-3-sulfate. To get a preliminary insight into the biological relevance of the newly discovered DON-sulfates, in vitroexperiments were performed. In contrast to DON, sulfate conjugates lacked potency to suppress protein translation. However, surprisingly we found that DON-sulfates enhanced proliferation of human HT-29 colon carcinoma cells, primary human colon epithelial cells (HCEC-1CT) and, to some extent, also T24 bladder cancer cells. A proliferative stimulus, especially in tumorigenic cells raises concern on the potential impact of DON-sulfates on consumer health. Thus, a further characterization of their toxicological relevance should be of high priority.

Design and Synthesis of Some New 1,3,4-Thiadiazines with Coumarin Moieties and Their Antioxidative and Antifungal Activity

A series of newly disubstituted (compounds 4a,b) and trisubstituted 1,3,4-thiadiazines 5a–l with various substituents was prepared utilizing different thiosemicarbazides and 3-α-bromoacetylcoumarins as starting compounds. The structures of the synthesized 1,3,4-thiadiazines are elucidated and confirmed utilizing the corresponding analytical and spectroscopic data. All of the new thiadiazine derivatives were tested for their antioxidant activity, employing different antioxidant assays (DPPH scavenging activity, iron chelating activity, power reducing activity). Compounds 5b, 5f, 5j and 4b were proven to be the best DPPH radical scavengers, while compounds 5h and 5j have shown the best iron chelating activity. Thiadiazine derivatives were also tested on their antifungal activity against four mycotoxicogenic fungi, Aspergillus flavus, A. ochraceus, Fusarium graminearum and F. verticillioides. The best antifungal against A. flavus was proven to be compound 5e, while compounds 4a and 5c were the best antifungals on A. ochraceus, and compound 5g showed the best antifungal activity on F. verticillioides.

Distribution of zearalenone in malted barley fractions dependent on Fusarium graminearum growing conditions

Zearalenone (ZON) distribution was measured in main fractions of malted barley, dependent on incubation time (17, 26, 34days), water activity (0.95 and 0.98) and temperature (20°C and 30°C). Malted samples were sterilised and inoculated with Fusarium graminearum. ZON levels were higher (p<0.01) in bran and germ than flour under almost all growing conditions. Incubation at 30°C resulted in generally lower ZON levels in germ and bran, regardless of aw and incubation time. After 34days, ZON levels in flour from samples that were incubated at the higher temperature rose significantly. At 20°C ZON concentration showed a bell-shaped concentration profile with increasing incubation time in bran and germ, whilst ZON levels in flour increased at aw 0.98 and dropped at the lower aw. The results indicate the importance of storage conditions for ZON levels in commercially relevant grain fractions of malted barley and help predict existing mycotoxin levels or manipulate storage conditions to reduce ZON content.

From malt to wheat beer: A comprehensive multi- toxin screening, transfer assessment and its influence on basic fermentation parameters

The aim was to determine the mycotoxin transfer rate into beer during a semi-industrial production process and the effect of fungicide treatment in the field on mycotoxins concentrations in beer. To ensure the usual practical agronomical conditions, sample A was treated with fungicide Prosaro® 250, and sample B was infected with Fusarium culmorum spores, in order to obtain infected malt. Malt was produced using standard procedure and beer was produced in a semi-industrial unit. During fermentation measurement of sugars (maltotriose and maltose), glycerol and ethanol content was performed on a daily basis. Multiple toxins were determined in malt and beer. Deoxynivalenol (DON), its modified plant metabolite DON-3-glucoside (DON-glucoside), brevianamide F, tryptophol, linamarin, lotaustralin, culmorin (CUL), 15-hydroxy-CUL and 5-hydroyx-CUL were detected in all samples. Results indicate that F. culmorum infection did not influence the fermentation process or the alcohol concentration.

Formulation and processing factors affecting trichothecene mycotoxins within industrial biscuit-making

Food processing, especially thermal treatment, may have implications on mycotoxins in products available for consumers. This research work aimed to study how mycotoxin levels may be influenced by modifying the technological parameters of both whole grain and cocoa biscuit-making processes. The study was mainly focused on the following mycotoxins: deoxynivalenol, deoxynivalenol-3-glucoside, and the minor metabolite culmorin. Special emphasis was given to the recipe formulation, and to the baking conditions, using an industrial-scale operation, starting from naturally contaminated raw materials. Exploiting the power of Design of Experiments (DoE) and a dedicated LC-MS/MS method, the complexity of the different processes was investigated. The models obtained within this study showed a high goodness-of-fit suggesting that the pH and the baking time play important roles for minimizing mycotoxins in the final products, while the recipe formulation has an impact on the mycotoxins extractability by affecting the biscuit microstructure.

Ultra-sensitive, stable isotope assisted quantification of multiple urinary mycotoxin exposure biomarkers

There is a critical need to better understand the patterns, levels and combinatory effects of exposures we are facing through our diet and environment. Mycotoxin mixtures are of particular concern due to chronic low dose exposures caused by naturally contaminated food. To facilitate new insights into their role in chronic disease, mycotoxins and their metabolites are quantified in bio-fluids as biomarkers of exposure. Here, we describe a highly sensitive urinary assay based on ultra-high performance liquid chromatography - tandem mass spectrometer (UHPLC-MS/MS) and 13C-labelled or deuterated internal standards covering the most relevant regulated and emerging mycotoxins. Utilizing enzymatic pre-treatment, solid phase extraction and UHPLC separation, the sensitivity of the method was significantly higher (10-160x lower LODs) than in a previously described method used for comparison purpose, and stable isotopes provided compensation for challenging matrix effects. This method was in-house validated and applied to re-assess mycotoxin exposure in urine samples obtained from Nigerian children, adolescent and adults, naturally exposed through their regular diet. Owing to the methods high sensitivity, biomarkers were detected in all samples. The mycoestrogen zearalenone was the most frequently detected contaminant (82%) but also ochratoxin A (76%), aflatoxin M1 (73%) and fumonisin B1 (71%) were quantified in a large share of urines. Overall, 57% of 120 urines were contaminated with both, aflatoxin M1 and fumonisin B1, and other co-exposures were frequent. These results clearly demonstrate the advanced performance of the method to assess lowest background exposures (pg mL-1 range) using a single, highly robust assay that will allow for the systematic investigation of low dose effects on human health.

Most common HCV genotypes in patients from north-eastern Croatia.

OBJECTIVE The aims of this study were to determine the HCV-RNA viral load, genotype distribution, risk factors and symptoms of HCVRNA positive viral load in HCV antibody-positive patients from north-eastern Croatia. MATERIALS AND METHODS From January 2009 to December 2011, 203 HCV antibody- positive patients (130 men and 73 women; median age 44.5 years) were analyzed for HCV-RNA by the COBAS TaqMan HCV test and genotyped by the Linear Array HCV Genotyping test (both from Roche). All patients completed a structured questionnaire about risk factors and symptoms. RESULTS The HCV-RNA percentage was 61.1% and was similar for men and women. The HCV-RNA viral load increased with age: while 55% of 20-50 year old patients were HCV-RNA positive, 73% of patients >50 years were positive (p=0.021). Genotype 1 was the most prevalent genotype (79.8%), followed by 3 (12.9%), 4 (6.5%), and 2 (0.8%); genotypes 5 and 6 were not determined. Patients with genotype 1 (median, 50 years) were older than patients with 3 (median, 33.5 years) or 4 (median, 38 years). The blood transfusions performed in Croatian hospitals before 1993 was significantly associated with HCV-RNA positive viral load (p<0.05). CONCLUSION These data indicated an elevated prevalence of genotype 1 in elderly HCV-RNA positive patients and it may continue to rise. Using RNA-based detection in HCV positive-antibody patients would allow early detection of HCV in the acute stage of HCV disease and the increased risk of HCV genotyperelated treatment failure.