José Vicente Gimeno-Adelantado

Recent research has showed that Aspergillus flavus and Aspergillus parasiticus are aflatoxigenic species that can become very competitive in the framework of climate change. Aflatoxins show carcinogenic, mutagenic, immunotoxic and teratogenic effects on human and animals. Effective and sustainable measures to inhibit these species and aflatoxins in food are required. Origanum vulgare and Cinnamomum zeylanicum essential oils (EOs) and their major active constituents, carvacrol and cinnamaldehyde, respectively, were assayed for inhibiting these species and aflatoxin production in maize extract medium under different environmental conditions. Doses of 10–1000 mg l⁻¹ were assayed and the effective doses for 50 (ED₅₀) and 90% (ED₉₀) growth inhibition were determined. The ED₅₀ of cinnamaldehyde, carvacrol, oregano EO, and cinnamon EO against A. flavus were in the ranges 49–52.6, 98–145, 152–505, 295–560 mg l⁻¹ and against A. parasiticus in the ranges 46–55.5, 101–175, 260–425 and 490–675 mg l⁻¹, respectively, depending on environmental conditions. In A. flavus treatments ED₉₀ were in the ranges 89.7–90.5, 770–860 and 820–>1000 mg l⁻¹ for cinnamaldehyde, carvacrol and cinnamon EO, and in A. parasiticus treatments in the ranges 89–91, 855–>1000 and 900–>1000 mg l⁻¹, respectively. ED₉₀ values for oregano EO against both species were >1000 mg l⁻¹. Growth rates of both species were higher at 37 than at 25°C and at 0.99 than at 0.96 a_w. Aflatoxin production was higher at 25 than at 37°C. Stimulation of aflatoxin production was observed at low doses except for cinnamaldehyde treatments. The effectiveness of EOs and their main constituents to inhibit fungal growth and aflatoxin production in contact assays was lower than in vapour phase assays using bioactive EVOH-EO films previously reported.

Aspergillus flavus is a highly aflatoxin (AF)-producing species infecting maize and other crops. It is dominant in tropical regions, but it is also considered an emerging problem associated with climate change in Europe. The aim of this study was to assess the efficacy of azole fungicides (prochloraz, tebuconazole and a 2:1 (w/w) mixture of prochloraz plus tebuconazole) to control the growth of A. flavus and AF production in yeast-extract–sucrose (YES) agar and in maize kernels under different water activities (a_w) and temperatures. Aflatoxins B₁ and B₂ were determined by LC with fluorescence detection and post-column derivatisation of AFB₁. In YES medium and maize grains inoculated with conidia of A. flavus, the growth rate (GR) of the fungus and AFB₁ and AFB₂ production were significantly influenced by temperature and treatment. In YES medium and maize kernels, optimal temperatures for GR and AF production were 37 and 25°C, respectively. In maize kernels, spore germination was not detected at the combination 37ºC/0.95 a_w; however, under these conditions germination was found in YES medium. All fungicides were more effective at 0.99 than 0.95 a_w, and at 37 than 25ºC. Fungicides effectiveness was prochloraz > prochloraz plus tebuconazole (2:1) > tebuconazole. AFs were not detected in cultures containing the highest fungicide doses, and only very low AF levels were found in cultures containing 0.1 mg l^–1 prochloraz or 5.0 mg l^–1 tebuconazole. Azoles proved to be highly efficient in reducing A. flavus growth and AF production, although stimulation of AF production was found under particular conditions and low-dosage treatments. Maize kernels were a more favourable substrate for AF biosynthesis than YES medium. This paper is the first comparative study on the effects of different azole formulations against A. flavus and AF production in a semi-synthetic medium and in maize grain under different environmental conditions.

An analytical method based on micellar liquid chromatography was developed to determine the concentration of three catecholamines (epinephrine, norepinephrine, and dopamine) in urine. The detection of these compounds in urine can be useful to diagnose several diseases, related to stress and sympathoadrenal system dysfunction, using a non-invasive collection procedure. The sample pretreatment was a simple dilution in a micellar solution, filtration, and direct injection, thus avoiding time-consuming and tedious extraction steps. Therefore, there is no need to use an internal standard. The three catecholamines were eluted using a C18 column and a mobile phase of 0.055 M sodium dodecyl sulfate-1.5 % methanol buffered at pH 3.8 running at 1.5 mL/min under isocratic mode in less than 25 min. The detection was performed by amperometry applying a constant potential of +0.5 V. The procedure was validated following the guidelines of the European Medicines Agency in terms of the following: calibration range (0.09–5 μg/mL), linearity (r ² > 0.9995), limit of detection (0.02 μg/mL), within- and between-run accuracy (−6.5 to +8.4 %) and precision (<10.2 %), dilution integrity, matrix effect, robustness (<8.4), and stability. The obtained values were below those required by the guide. The method was rapid, easy-to-handle, eco-friendly, and safe and provides reliable quantitative data, and is thus useful for routine analysis. The procedure was applied to the analysis of epinephrine, norepinephrine, and dopamine in urine samples from patients of a local hospital.

The use of the scanning electrochemical microscopy (SECM) technique for identifying and mapping of both organic and inorganic pigments in sub-microsamples from pictorial specimens is described.

Maya Blue-type specimens prepared from indigo (1 wt %) plus kaolinite, montmorillonite, palygorskite, sepiolite, and silicalite are studied. Liquid chromatography with diode array detection, ultra-performance liquid chromatography coupled with mass spectrometry, and pyrolysis-silylation gas chromatography–mass spectrometry analyses of the extracts from these specimens combined with spectral and solid-state voltammetry, electrochemical impedance spectroscopy, and scanning electrochemical microscopy techniques provide evidence for the presence of a significant amount of dehydroindigo and isatin accompanying indigo and other minority organic compounds in all samples. Solid-state electrochemistry data permits the estimatation of indigo loading in archeological Maya Blue, which is in the range of 0.2 to 1.5 wt %. These results support a view of ‘genuine’ Maya Blue-type materials as complex polyfunctional organic–inorganic hybrids.