NMR spectroscopic study of cyclodextrin inclusion complexes with A-007 prodrugs

Encapsulation of thiabendazole in hydroxypropyl-β-cyclodextrin nanofibers via polymer-free electrospinning and its characterization

BACKGROUND

Thiabendazole (TBZ) is a poorly water-soluble benzimidazole fungicide. However, the water solubility of TBZ can be significantly enhanced by inclusion complexation with cyclodextrins. In this study, a thiabendazole/hydroxypropyl-β-cyclodextrin (TBZ/HPβCD) complex was synthesized and electrospinning was performed to produce a TBZ/HPβCD nanofibrous (TBZ/HPβCD-NF) complex that improved water solubility and antifungal activity.

RESULTS

The formation of TBZ/HPβCD-NF was characterized by Fourier transform infrared spectroscopy, X-ray diffraction and nuclear magnetic resonance. The morphology of TBZ/HPβCD-NF was studied by scanning electron microscopy. A phase solubility experiment showed that HPβCD exerted a great solubilization effect on TBZ, and TBZ/HPβCD-NF had better antifungal activity compared to that of TBZ alone.

CONCLUSIONS

In summary, the solid fungicidal nanodispersion prepared in the present study is a new type of formulation that can enhance the water solubility of TBZ. This formulation, which demonstrated potential as a new fast dissolving formulation type with increased efficacy, is expected to be conducive to the sustainable development of agriculture. © 2020 Society of Chemical Industry.

Preferential solvation of thiophene and furan-2-carboxaldehyde phenylhydrazone derivatives in DMSO-water and DMSO-n-octanol mixtures

The preferential solvation of thiophene- and furan-2-carboxaldehyde phenylhydrazone derivatives in DMSO-water and DMSO-n-octanol mixtures has been studied using visible absorption spectroscopy with a previous characterization of the electronic transitions by Time-Dependent Density Functional Theory (TDDFT) and solvatochromic study in several solvents with different hydrogen-bond donor capacity. The results indicate that the phenylhydrazones are preferentially solvated by clusters of DMSO-water existing in the solvent mixture and the dielectric enrichment as preferential solvation mechanism was discarded. A relation between local DMSO concentration with nitro groups and the electronegativity of the heteroatom of the five-membered ring was found. For DMSO-1-octanol mixtures, the results showed no preferential solvation.

Inclusion interaction of chloramphenicol and heptakis (2,6-di-O-methyl)-β-cyclodextrin: phase solubility and spectroscopic methods

The inclusion interaction between chloramphenicol and heptakis (2,6-di-O-methyl)-β-cyclodextrin (DMBCD) had been investigated by phase solubility and spectroscopic methods such as UV-vis spectroscopy, circular dichroism, Fourier transform infrared (FT-IR) spectroscopy, proton nuclear magnetic resonance spectroscopy ((1)H NMR) as well as 2D-ROESY spectra. Phase solubility analysis showed A(L)-type diagram with DMBCD, which suggested the formation of 1:1 inclusion complex of DMBCD with chloramphenicol. The estimated stability constant (K(s)) of the inclusion complex of chloramphenicol with DMBCD is 493 M(-1) at 293 K. The solubility enhancement of chloramphenicol in the presence of DMBCD is stronger than that in the presence of β-CD, HP-β-CD and M-β-CD. The results obtained by spectroscopic methods showed that the nitrophenyl moiety of chloramphenicol is deeply inserted into inner cavity of DMBCD from the narrow rim of DMBCD, which the inclusion model of chloramphenicol with DMBCD differs from that with β-CD.

Electrospray-ionization mass spectrometry study of cyclodextrin complexes with A007 prodrugs

Electrospray-ionization mass spectrometric (ESIMS) studies of several A007 prodrugs in aqueous cyclomaltohexaose (alpha-cyclodextrin, alpha-CD), cyclomaltoheptaose (beta-cyclodextrin, beta-CD), and cyclomaltooctaose (gamma-cyclodextrin, gamma-CD) were performed. The acetic acid derivative of A007 should metabolize in vivo before becoming the A007 prodrug, while on the other hand, the glycine-modified A007 prodrug has surfactant-like physical properties and slowly hydrolyzed in the aqueous cyclodextrins by releasing free A007. ESIMS studies give insight into the process of prodrug hydrolysis in the presence of cyclodextrins and, hence, the influence of cyclodextrins on the timely release of the A007 prodrug. Formation of various molecular aggregates and cyclodextrin inclusion complexes of A007 prodrugs and their hydrolyzed products was demonstrated by ESIMS.