Residue behavior and risk assessment of pyraclostrobin and tebuconazole in peppers under different growing conditions

This study evaluates the residue behavior and risks of pyraclostrobin and tebuconazole in peppers. An analytical method for the simultaneous determination of the concentration of these fungicides in peppers was developed using ultra-high performance liquid chromatography-triple quadrupole mass spectrometry. Pepper samples were extracted with acetonitrile and cleaned with primary secondary amine and graphitized carbon black. The average recoveries of pyraclostrobin and tebuconazole under three fortification levels were 86.7-101.4% and 81.7-104.4%, with relative standard deviations of 4.0-7.2% and 3.8-10.9%, respectively. The limit of quantification of both fungicides in peppers was 0.01 mg/kg. The terminal residue trial of 30% pyraclostrobin and tebuconazole suspension concentrate was investigated for samples cultivated in open fields and greenhouses. The results showed that the terminal residues of pyraclostrobin and tebuconazole in peppers were lower than the maximum residue limits established by GB 2763-2021 (0.5 mg/kg for pyraclostrobin and 2 mg/kg for tebuconazole). The results of a statistical t-test indicated that there was no significant difference between samples grown in open fields and greenhouses. According to the international estimate of short-term intake (IESTI) calculation model, provided by the Joint FAO/WHO Meeting on Pesticide Residues, the acute dietary exposure risk of both fungicides in peppers was acceptable for the general population, with an IESTI of 0-3% and 0-5% of the acute reference dose for pyraclostrobin and tebuconazole, respectively.

Separation of nordihydrocapsiate from capsiate and major capsaicinoid analogues using ultra high performance liquid chromatography

Accurate, rapid quantitation of the capsaicinoid and capsinoid compounds produced by peppers (Capsicum spp.) is essential to assess quality. Here, we developed a rapid ultra-high performance liquid chromatography method for the simultaneous separation of five major capsaicinoids and three major capsinoids from peppers. Optimal chromatographic separation was achieved using a phenyl-hexyl stationary phase with a mobile phase of acidified water and methanol with a flow rate of 0.5 ml/min at a column temperature of 55 °C over 5 min. The method was validated by testing linearity, precision, robustness, and limits of detection and quantification. The developed method was successfully employed to profile capsaicinoids and capsinoids from different pepper cultivars. Out of the 10 pepper cultivars analysed, all three major capsinoids were detected in two cultivars. To the best of our knowledge, this is the first report of successful separation of nordihydrocapsiate from capsiate and quantification of nordihydrocapsiate.

Genome-wide identification of the Capsicum bHLH transcription factor family: discovery of a candidate regulator involved in the regulation of species-specific bioactive metabolites

BACKGROUND

The basic helix-loop-helix (bHLH) transcription factors (TFs) serve crucial roles in regulating plant growth and development and typically participate in biological processes by interacting with other TFs. Capsorubin and capsaicinoids are found only in Capsicum, which has high nutritional and economic value. However, whether bHLH family genes regulate capsorubin and capsaicinoid biosynthesis and participate in these processes by interacting with other TFs remains unknown.

RESULTS

In this study, a total of 107 CabHLHs were identified from the Capsicum annuum genome. Phylogenetic tree analysis revealed that these CabHLH proteins were classified into 15 groups by comparing the CabHLH proteins with Arabidopsis thaliana bHLH proteins. The analysis showed that the expression profiles of CabHLH009, CabHLH032, CabHLH048, CabHLH095 and CabHLH100 found in clusters C1, C2, and C3 were similar to the profile of carotenoid biosynthesis in pericarp, including zeaxanthin, lutein and capsorubin, whereas the expression profiles of CabHLH007, CabHLH009, CabHLH026, CabHLH063 and CabHLH086 found in clusters L5, L6 and L9 were consistent with the profile of capsaicinoid accumulation in the placenta. Moreover, CabHLH007, CabHLH009, CabHLH026 and CabHLH086 also might be involved in temperature-mediated capsaicinoid biosynthesis. Yeast two-hybrid (Y2H) assays demonstrated that CabHLH007, CabHLH009, CabHLH026, CabHLH063 and CabHLH086 could interact with MYB31, a master regulator of capsaicinoid biosynthesis.

CONCLUSIONS

The comprehensive and systematic analysis of CabHLH TFs provides useful information that contributes to further investigation of CabHLHs in carotenoid and capsaicinoid biosynthesis.

Root distribution with the use of drip irrigation on layered soils at greenhouses crops

Greenhouse cultivation has proven to be an efficient solution to extra-early horticultural production, allowing the cycle of vegetable production to be closed throughout the year. This efficient solution depends on many factors, perhaps the main one being the localized irrigation system. On the other hand, the availability of water for irrigation will be one of the most limiting factors for the development of this agricultural practice. The permanent search for improving irrigation efficiency must be considered as one of the great challenges of sustainable agriculture and in the interest of environmental conservation. In this study, the distribution of the roots of the two main horticultural crops, tomato (Solanum lycopersicum L.) and peppers (Capsicum annuum L.), has been analyzed with the localized irrigation system. In addition, they have been studied for layered soils, which represent an advance in terms of resources, since they are artificial soils, where the natural soil does not allow a horticultural crop. It has been found for these stratified soils, that in pepper crop 90% of the root density is in the soil layer 0 to 9 cm. However, for tomato crops 90% of the root density is in the soil layer from 0 to 11 or 15.5 cm according to the type of soil, in other words filling almost all the added soil. The results obtained in this research allow the Hydrus 3D model for stratified soils to be calibrated. This work allows opening new perspectives in the efficient management of adding soils for new greenhouse construction and for localized irrigation of horticultural crops in general, tomato, and peppers in particular.

Simultaneous determination by UHPLC-PDA of major capsaicinoids and capsinoids contents in peppers

Capsaicinoids and capsinoids compounds have been a focus of special attention for their health benefits. An effective and rapid Ultra-High-Performance Liquid Chromatography (UHPLC-PDA) method has been developed and validated for the simultaneous separation and quantitative determination of the major capsaicinoids and capsinoids present in peppers. The separation of all the compounds of interest was achieved in less than 2 min by means of an ACQUITY UPLC BEH rp-C18 column (100 mm × 2.1 mm i.d., 1.7 µm particle size). The variables that have been optimized are the mobile phase (water as solvent A and acetonitrile as solvent B, both acidified by adding 0.1% acetic acid), separation gradient, column temperature (35-70 °C), flow rate (0.6-0.95 mL min^-1), and injection volume (2.5-3.5 µL). The evaluation of the chromatographic performance revealed excellent resolution, retention factor, and selectivity. The method was satisfactorily validated in terms of linearity, detection and quantification limits, precision, and robustness.

Capsaicin-like analogue induced selective apoptosis in A2058 melanoma cells: Design, synthesis and molecular modeling

The use of molecules inspired by natural scaffolds has proven to be a very promising and efficient method of drug discovery. In this work, capsaicin, a natural product from Capsicum peppers with antitumor properties, was used as a prototype to obtain urea and thiourea analogues. Among the most promising compounds, the thiourea compound 6g exhibited significant cytotoxic activity against human melanoma A2058 cells that was twice as high as that of capsaicin. Compound 6g induced significant and dose-dependent G₀/G₁ cell cycle arrest in A2058 cells triggering cell death by apoptosis. Our results suggest that 6g modulates the RAF/MEK/ERK pathway, inducing important morphological changes, such as formation of apoptotic bodies and increased levels of cleaved caspase-3. Compared to capsaicin, 6g had no significant TRPV1/6 agonist effect or irritant effects on mice. Molecular modeling studies corroborate the biological findings and suggest that 6g, besides being a more reactive molecule towards its target, may also present a better pharmacokinetic profile than capsaicin. Inverse virtual screening strategy found MEK1 as a possible biological target for 6g. Consistent with these findings, our observations suggested that 6g could be developed as a potential anticancer agent.

Fast analysis of capsaicinoids in Naga Jolokia extracts (Capsicum chinense) by high-performance liquid chromatography using fused core columns

A rapid high-performance liquid chromatography method with a C18 reverse-phase fused-core column has been developed for the determination and quantification of the main capsaicinoids (nornordihydrocapsaicin, nordihydrocapsaicin, capsaicin, dihydrocapsaicin, homocapsaicin and homodihydrocapsaicin) present in Naga Jolokia peppers. A fused-core Kinetex™ C18 column (50×2.1mm i.d.; 2.6μm) was used for the analysis. The chromatographic separation was obtained with a gradient method in which the mobile phase was water (0.1% acetic acid) as solvent A and acetonitrile (0.1% acetic acid) as solvent B. The separation of all compounds was achieved in less than 3min with a total analysis time (sample-to-sample) of 10min. The robustness of the method was evaluated. The method showed excellent repeatability and intermediate precision expressed as coefficient of variance of less than 2%. The developed method was employed for the quantification of the major capsaicinoids present in different peppers and commercial products containing chilli peppers.