betadex and triadimefon

Chiral separation of 12 new triadimenol antifungal active compounds by electrokinetic chromatography and chiral recognition mechanisms by computer-aided molecular modeling techniques were studied. Seven neutral cyclodextrins were used as chiral selectors. Heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD) exhibited a very high enantioselectivity power to 12 active compounds compared to the other tested CDs. The influences of the concentration of TM-β-CD, buffer pH, buffer concentration, applied voltage, and temperature were investigated, respectively. Under the optimum separation conditions, all the 12 active compounds were baseline separated and the resolutions of most compounds were beyond 2.50. The study of the analyte structure-enantioseparation relationships showed that substitutions in the side chains played important roles on enantiomeric separation. By means of computer-aided molecular modeling software Discovery Studio 2.5/Sybyl 7.0/Gold 3.0.1, inclusion process between TM-β-CD and these enantiomers was investigated and their binding energies were calculated. The results suggested that the enantioseparation result related to the difference in binding energy. And the good separation obtained in the presence of the TM-β-CD chiral selector was due to the big binding energy difference of two enantiomers with the chiral selector.

Topics: Antifungal Agents; beta-Cyclodextrins; Chromatography, Micellar Electrokinetic Capillary; Hydrogen-Ion Concentration; Molecular Docking Simulation; Stereoisomerism; Temperature; Triazoles

The photochemistry of pesticides triadimenol and triadimefon was studied on cellulose and beta-cyclodextrin (beta-CD) in controlled and natural conditions, using diffuse reflectance techniques and chromatographic analysis. The photochemistry of triadimenol occurs from the chlorophenoxyl moiety, while the photodegradation of triadimefon also involves the carbonyl group. The formation of 4-chlorophenoxyl radical is one of the major reaction pathways for both pesticides and leads to 4-chlorophenol. Triadimenol also undergoes photooxidation and dechlorination, leading to triadimefon and dechlorinated triadimenol, respectively. The other main reaction process of triadimefon involves alpha-cleavage from the carbonyl group, leading to decarbonylated compounds. Triadimenol undergoes photodegradation at 254 nm but was found to be stable at 313 nm, while triadimefon degradates in both conditions. Both pesticides undergo photochemical decomposition under solar radiation, being the initial degradation of rate per unit area of triadimefon 1 order of magnitude higher than the observed for triadimenol in both supports. The degradation rates of the pesticides were somewhat lower in beta-CD than on cellulose. Photoproduct distribution of triadimenol and triadimefon is similar for the different irradiation conditions, indicating an intramolecular energy transfer from the chlorophenoxyl moiety to the carbonyl group in the latter pesticide.

Topics: Adsorption; beta-Cyclodextrins; Cellulose; Cyclodextrins; Fungicides, Industrial; Gas Chromatography-Mass Spectrometry; Kinetics; Molecular Structure; Pesticide Residues; Pesticides; Photochemistry; Spectrophotometry; Triazoles

Enantiomeric separation of two triazole fungicides, triadimefon and triadimenol, was investigated in sulfated beta-cyclodextrin (sulfated beta-CD)-mediated capillary electrophoresis (CE) systems. It was found that, at pH 2-4, sulfated beta-CD exhibited strong chiral recognition towards both triadimefon and triadimenol. The enantiorecognition was believed to result from the multiple interactions between sulfated beta-CD and the analytes, which included inclusion effect, electrostatic interaction, and hydrogen bonding. Under optimal conditions (phosphate buffer with 2% sulfated beta-CD, pH 2.5), simultaneous resolution of all chiral isomers of triadimefon and triadimenol was achieved in less than half an hour. In conjunction with solvent extraction and subsequent enrichment by solid-phase extraction (SPE), this new enantioseparation method was applied successfully in the study of stereoselectivity associated with the biotransformation of triadimefon to triadimenol by soil microorganisms. The present methodology was superior to the commonly adopted chiral gas chromatography (GC) approach in that a very mild procedure was involved from sample extraction to the ultimate chiral separation. Thus, the disturbance of the enantiomeric distribution patterns of the original soil samples by heat stress was an unlikely scenario. Furthermore, it was discovered that, owing to the unique selectivity of the present separation strategy, there was virtually no interference from the soil matrix, which led to improvements in both sensitivity and selectivity in real sample determination.

Topics: beta-Cyclodextrins; Buffers; Chromatography, Gas; Chromatography, Micellar Electrokinetic Capillary; Cyclodextrins; Electrophoresis, Capillary; Fungicides, Industrial; Hydrogen-Ion Concentration; Molecular Structure; Reference Standards; Stereoisomerism; Time Factors; Triazoles