scholarly journals Synthesis of zearalenone-16-β,D-glucoside and zearalenone-16-sulfate: A tale of protecting resorcylic acid lactones for regiocontrolled conjugation

2014 ◽  
Vol 10 ◽  
pp. 1129-1134 ◽  
Author(s):  
Hannes Mikula ◽  
Julia Weber ◽  
Dennis Svatunek ◽  
Philipp Skrinjar ◽  
Gerhard Adam ◽  
...  
Keyword(s):  
Natural Product ◽  
Reference Materials ◽  
High Stability ◽  
Protective Group ◽  
Masked Mycotoxins ◽  
Type Compound ◽  
Acid Lactone ◽  
Reliable Procedure ◽  
Resorcylic Acid Lactones

The development of a reliable procedure for the synthesis of the 16-glucoside and 16-sulfate of the resorcylic acid lactone (RAL) type compound zearalenone is presented. Different protective group strategies were considered and applied to enable the preparation of glucosides and sulfates that are difficult to access up to now. Acetyl andp-methoxybenzyl protection led to undesired results and were shown to be inappropriate. Finally, triisopropylsilyl-protected zearalenone was successfully used as intermediate for the first synthesis of the corresponding mycotoxin glucoside and sulfate that are highly valuable as reference materials for further studies in the emerging field of masked mycotoxins. Furthermore, high stability was observed for aryl sulfates prepared as tetrabutylammonium salts. Overall, these findings should be applicable for the synthesis of similar RAL type and natural product conjugates.

scholarly journals The Importance of Reference Materials and Method Validation for Advancing Research on the Health Effects of Dietary Supplements and Other Natural Products

2021 ◽  
Vol 8 ◽  
Author(s):  
Sanem Hosbas Coskun ◽  
Stephen A. Wise ◽  
Adam J. Kuszak
Keyword(s):  
Natural Products ◽  
Dietary Supplements ◽  
Natural Product ◽  
Health Effects ◽  
Reference Materials ◽  
Plant Material ◽  
Herbal Remedies ◽  
Reproducible Research ◽  
Biological Specimen ◽  
Product Characterization

Insufficient assessment of the identity and chemical composition of complex natural products, including botanicals, herbal remedies, and dietary supplements, hinders reproducible research and limits understanding mechanism(s) of action and health outcomes, which in turn impede improvements in clinical practice and advances in public health. This review describes available analytical resources and good methodological practices that support natural product characterization and strengthen the knowledge gained for designing and interpreting safety and efficacy investigations. The practice of validating analytical methods demonstrates that measurements of constituents of interest are reproducible and appropriate for the sample (e.g., plant material, phytochemical extract, and biological specimen). In particular, the utilization of matrix-based reference materials enables researchers to assess the accuracy, precision, and sensitivity of analytical measurements of natural product constituents, including dietary ingredients and their metabolites. Select case studies are presented where the careful application of these resources and practices has enhanced experimental rigor and benefited research on dietary supplement health effects.

scholarly journals Characterization of the Biosynthetic Genes for 10,11-Dehydrocurvularin, a Heat Shock Response-Modulating Anticancer Fungal Polyketide from Aspergillus terreus

2013 ◽  
Vol 79 (6) ◽  
pp. 2038-2047 ◽  
Author(s):  
Yuquan Xu ◽  
Patricia Espinosa-Artiles ◽  
Vivien Schubert ◽  
Ya-ming Xu ◽  
Wei Zhang ◽  
...  
Keyword(s):  
Heat Shock ◽  
Heat Shock Response ◽  
Aspergillus Terreus ◽  
Polyketide Synthase ◽  
Polyketide Synthases ◽  
Content Type ◽  
Shock Response ◽  
Starter Unit ◽  
Acid Lactone ◽  
Resorcylic Acid Lactones

ABSTRACT10,11-Dehydrocurvularin is a prevalent fungal phytotoxin with heat shock response and immune-modulatory activities. It features a dihydroxyphenylacetic acid lactone polyketide framework with structural similarities to resorcylic acid lactones like radicicol or zearalenone. A genomic locus was identified from the dehydrocurvularin producer strainAspergillus terreusAH-02-30-F7 to reveal genes encoding a pair of iterative polyketide synthases (A. terreusCURS1 [AtCURS1] and AtCURS2) that are predicted to collaborate in the biosynthesis of 10,11-dehydrocurvularin. Additional genes in this locus encode putative proteins that may be involved in the export of the compound from the cell and in the transcriptional regulation of the cluster. 10,11-Dehydrocurvularin biosynthesis was reconstituted inSaccharomyces cerevisiaeby heterologous expression of the polyketide synthases. Bioinformatic analysis of the highly reducing polyketide synthase AtCURS1 and the nonreducing polyketide synthase AtCURS2 highlights crucial biosynthetic programming differences compared to similar synthases involved in resorcylic acid lactone biosynthesis. These differences lead to the synthesis of a predicted tetraketide starter unit that forms part of the 12-membered lactone ring of dehydrocurvularin, as opposed to the penta- or hexaketide starters in the 14-membered rings of resorcylic acid lactones. TetraketideN-acetylcysteamine thioester analogues of the starter unit were shown to support the biosynthesis of dehydrocurvularin and its analogues, with yeast expressing AtCURS2 alone. Differential programming of the product template domain of the nonreducing polyketide synthase AtCURS2 results in an aldol condensation with a different regiospecificity than that of resorcylic acid lactones, yielding the dihydroxyphenylacetic acid scaffold characterized by an S-type cyclization pattern atypical for fungal polyketides.

Layered and ion implantation specimens as possible reference materials for the electron-probe microanalysis

1992 ◽  
Vol 50 (2) ◽  
pp. 1652-1653
Author(s):  
G. Remond ◽  
R.H. Packwood ◽  
C. Gilles ◽  
S. Chryssoulis
Keyword(s):  
Ion Implantation ◽  
Reference Materials ◽  
Analytical Techniques ◽  
Thin Film Deposition ◽  
Film Deposition ◽  
X Ray ◽  
Spatially Resolved ◽  
Analytical Expressions ◽  
Original Approach ◽  
Depth Concentration

Merits and limitations of layered and ion implanted specimens as possible reference materials to calibrate spatially resolved analytical techniques are discussed and illustrated for the case of gold analysis in minerals by means of x-ray spectrometry with the EPMA. To overcome the random heterogeneities of minerals, thin film deposition and ion implantation may offer an original approach to the manufacture of controlled concentration/ distribution reference materials for quantification of trace elements with the same matrix as the unknown.In order to evaluate the accuracy of data obtained by EPMA we have compared measured and calculated x-ray intensities for homogeneous and heterogeneous specimens. Au Lα and Au Mα x-ray intensities were recorded at various electron beam energies, and hence at various sampling depths, for gold coated and gold implanted specimens. X-ray intensity calculations are based on the use of analytical expressions for both the depth ionization Φ (ρz) and the depth concentration C (ρz) distributions respectively.

Synthetic studies toward inducamide C

2021 ◽  
Author(s):  
Ardalan A. Nabi ◽  
Lydia M. Scott ◽  
Daniel P. Furkert ◽  
Jonathan Sperry
Keyword(s):  
Natural Product ◽  
Structural Revision ◽  
Synthetic Studies

The rare benzoxazepine ring in the alkaloid inducamide C is unstable and prone to rearrangement, indicating that structural revision of the natural product may be necessary.

Lessons learned from the optimization of natural product based kinase inhibitors through molecular calculations

Planta Medica ◽  
2008 ◽  
Vol 74 (09) ◽  
Author(s):  
V Myrianthopoulos ◽  
P Magiatis ◽  
AL Skaltsounis ◽  
L Meijer ◽  
E Mikros
Keyword(s):  
Natural Product ◽  
Kinase Inhibitors ◽  
Lessons Learned ◽  
Molecular Calculations
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