Variations in polyamine conjugates in maize (Zea mays L.) seeds contaminated with aflatoxin B1: a dose-response relationship.

BACKGROUND: Cereal seeds, such as maize seeds, are frequently contaminated with aflatoxin B1 (AFB1), one of the most dangerous naturally occurring carcinogens. In plants, phenolamides are involved in biotic stress response. The data on variations of phenolamides in AFB1-containing seeds are limited. RESULTS: Five polyamine conjugates, including two spermidine and three putrescine conjugates, were tentatively identified in methanolic extracts, using HPLC-DAD-MS. The ratio of putrescine to spermidine conjugates changed with increasing AFB1 concentration in a logistic dose-response manner, with a ratio of below 1 up to a concentration of 51.51 µg kg-1 , and approximately 2.54 and 3 at higher concentrations of 177.4 and 308.13 µg kg-1 , respectively. The observed variations of the total antioxidant activity and the total phenolic content may support this biphasic behaviour of the seeds against AFB1 stress. CONCLUSIONS: The obtained data are a contribution to the understanding of the roles of polyamine conjugates in seed defence to increasing AFB1 concentrations. According to our knowledge, this study reports for the first time the biphasic response of maize seeds to increasing AFB1 contamination level, comprising the induction of polyamine conjugate accumulation and variation in the ratio of conjugates. This dose-response relationship may provide useful information in the field of agricultural and food chemistry as an indicator of AFB1 contamination level and, hence, for selecting an appropriate seed quality. © 2020 Society of Chemical Industry.

Multivariate Curve Resolution - Alternate Least Square Analysis of Excitation-Emission Matrices for Maize Flour Contaminated with Aflatoxin B1.

In this preliminary study, we used the Multivariate Curve Resolution- Alternating Least Squares (MCR-ALS) algorithm to analyze the excitation-emission matrix for different samples of maize flour contaminated with aflatoxin B1 (AFB1) - uncontaminated, low-contaminated, high-contaminated and flour from the local market. We intended to see if there are differences in emission spectral parameters that depend on degree of contamination. The analysis used genuine emission of the fluorophores in the flour, in absence and presence of AFB1, which enables fast screening of the samples, without sample pre-processing. As a result of the analysis, two fluorescence components were derived from the emission spectra for all analyzed samples. The components' positions were the same for the uncontaminated reference sample and the commercial flour sample from the local market, whereas for the samples contaminated with the aflatoxin B1, the emitted peaks' positions were red-shifted. We found that the ratio of the areas of these two components is proportional to the intensity of contamination: 0.071 for uncontaminated sample, 0.090 for the sample from local market, 0.192 for low-contaminated sample and 1.431 for high-contaminated sample. These results indicate that fluorescence EEM coupled with MCR-ALS could be used for rapid and simple estimation of the degree AFB1 contamination in maize flour.

Intrinsic Fluorescence Markers for Food Characteristics, Shelf Life, and Safety Estimation: Advanced Analytical Approach.

Food is a complex matrix of proteins, fats, minerals, vitamins, and other components. Various analytical methods are currently used for food testing. However, most of the used methods require sample preprocessing and expensive chemicals. New analytical methods are needed for quick and economic measurement of food quality and safety. Fluorescence spectroscopy is a simple and quick method to measure food quality, without sample preprocessing. This technique has been developed for food samples due to the application of a front-face measuring setup. Fluorescent compounds-fluorophores in the food samples are highly sensitive to their environment. Information about molecular structure and changes in food samples is obtained by the measurement of excitation-emission matrices of the endogenous fluorophores and by applying multivariate chemometric tools. Synchronous fluorescence spectroscopy is an advantageous screening mode used in food analysis. The fluorescent markers in food are amino acids tryptophan and tyrosine; the structural proteins collagen and elastin; the enzymes and co-enzymes NADH and FAD; vitamins; lipids; porphyrins; and mycotoxins in certain food types. The review provides information on the principles of the fluorescence measurements of food samples and the advantages of this method over the others. An analysis of the fluorescence spectroscopy applications in screening the various food types is provided.

Explainable AI for unveiling deep learning pollen classification model based on fusion of scattered light patterns and fluorescence spectroscopy.

Pollen monitoring have become data-intensive in recent years as real-time detectors are deployed to classify airborne pollen grains. Machine learning models with a focus on deep learning, have an essential role in the pollen classification task. Within this study we developed an explainable framework to unveil a deep learning model for pollen classification. Model works on data coming from single particle detector (Rapid-E) that records for each particle optical fingerprint with scattered light and laser induced fluorescence. Morphological properties of a particle are sensed with the light scattering process, while chemical properties are encoded with fluorescence spectrum and fluorescence lifetime induced by high-resolution laser. By utilizing these three data modalities, scattering, spectrum, and lifetime, deep learning-based models with millions of parameters are learned to distinguish different pollen classes, but a proper understanding of such a black-box model decisions demands additional methods to employ. Our study provides the first results of applied explainable artificial intelligence (xAI) methodology on the pollen classification model. Extracted knowledge on the important features that attribute to the predicting particular pollen classes is further examined from the perspective of domain knowledge and compared to available reference data on pollen sizes, shape, and laboratory spectrofluorometer measurements.

Using Front-Face Fluorescence Spectroscopy and Biochemical Analysis of Honey to Assess a Marker for the Level of Varroa destructor Infestation of Honey Bee (Apis mellifera) Colonies.

Varroa destructor is a parasitic mite responsible for the loss of honey bee (Apis mellifera) colonies. This study aimed to find a promising marker in honey for the bee colony infestation level using fluorescence spectroscopy and biochemical analyses. We examined whether the parameters of the honey samples' fluorescence spectra and biochemical parameters, both related to proteins and phenolics, may be connected with the level of honey bee colonies' infestation. The infestation level was highly positively correlated with the catalase activity in honey (r = 0.936). Additionally, the infestation level was positively correlated with the phenolic spectral component (r = 0.656), which was tentatively related to the phenolics in honey. No correlation was found between the diastase activity in honey and the colonies' infestation level. The results indicate that the catalase activity in honey and the PFC1 spectral component may be reliable markers for the V. destructor infestation level of the colonies. The obtained data may be related to the honey yield obtained from the apiaries.

Cell wall response to UV radiation in needles of Picea omorika.

The UV-B represents the minor fraction of the solar spectrum, while UV-C is not contained in natural solar radiation, but both radiation types can cause damaging effects in plants. Cell walls (CWs) are one of the targets for external stressors. Juvenile P. omorika trees were treated either with 21 day-high doses UV-B or with 7 day- UV-C in open-top chambers. Using spectroscopic and biochemical techniques, it was shown that the response to UV radiation includes numerous modifications in needle CW structure: relative content of xylan, xyloglucan, lignin and cellulose decreased; cellulose crystallinity changed; yield of lignin monomers with stronger connection of CC in side chain with the ring increased; re-distribution of inter- and intra-polymer H-bonds occurred. The recovery was mediated by an increase in the activities and changes in isoform profiles of CW bound covalent peroxidases (POD) and polyphenol oxidases (PO) (UV-B), and ionic POD and covalent PO (UV-C). A connection between activities of specific POD/PO isoforms and phenolic species (m- and p-coumaric acid, pinoresinol and cinnamic acid derivatives) was demonstrated, and supported by changes in the sRNA profile. In vivo fluorometry showed phenolics accumulation in needle epidermal CWs. These results imply transversal connections between polymers and changed mechanical properties of needle CW as a response to UV. The CW alterations enabled maintenance of physiological functions, as indicated by the preserved chlorophyll content and/or organization. The current study provides evidence that in conifers, needle CW response to both UV-B and UV-C includes biochemical modifications and structural remodeling.

Moderate hyperhomocysteinemia induced by short-term dietary methionine overload alters bone microarchitecture and collagen features during growth.

AIMS: In general, hyperhomocysteinemia is increasingly appreciated as a risk factor for various diseases, including osteoporosis. However, its effects in non-adults remain largely unknown. Our aim was to determine whether dietary-caused increased homocysteine levels have deleterious effects on bone structure during growth. MAIN METHODS: We developed a model of moderate hyperhomocysteinemia caused by short-term methionine nutritional overload in growing rats. 30-days-old male Wistar albino rats were randomly assigned to either experimental group subject to a 30-days hypermethionine diet or control group. High-resolution 3D assessment of bone geometry and microarchitecture, as well as fluorescence spectroscopic analysis of bone matrix were performed. KEY FINDINGS: Short-term moderate hyperhomocysteinemia (~30µmol/L) achieved in the study notably affected bone and cartilage characteristics. Parameters of the cortical bone geometry in the experimental group indicated peculiar reorganization of the bone cross-section. Trabecular bone microarchitecture was especially sensitive to hyperhomocysteinemia showing clearly negative bone balance in the experimental group (almost 30% reduced bone volume, mainly due to ~25% decrease in trabecular number as well as markedly reduced trabecular connections). Fluorescent spectroscopy of bone matrix revealed multiple alterations to collagen spectra due to homocysteine accumulation in bone, indicative of broken collagenous cross-links. SIGNIFICANCE: Given that appropriate accrual of bone mass during growth has important effects on the risk of osteoporosis in adulthood, understanding the skeletal effects of dietary-induced hyperhomocysteinemia in non-adults is essential for interpreting its importance as a modifiable risk factor for osteoporosis and improving programs to preserve/re-establish bone health.