ABSTRACT
The molecular structure of mycotoxins enniatin B and beauvericin, which are used as ionophores, was studied using density functional theory in various symmetry groups and singly charged states. We have shown that the charge addition or removal causes significant structural changes. Unlike the neutral C3 molecules, the stability of the charged C1 structures was explained by the Jahn-Teller or Pseudo-Jahn-Teller effect. This finding agrees with the available experimental X-ray structures of their metal complexes where electron density transfer from the metal can be expected. Hence, the membrane permeability of metal sandwich-structure complexes possessing antimicrobial activities is modulated by the conformational changes.
ABSTRACT
In this paper, the molecular and electronic structure of curcumin is studied. High-symmetric gas-phase tautomers and their deprotonated forms in various symmetry groups are identified. The stability of lower-symmetry structures was explained by using the Pseudo-Jahn-Teller (PJT) effect. This effect leads to stable structures of different symmetries for the neutral enol and keto forms. The presented analysis demonstrated the potential significance of the PJT effect, which may modulate the setting of electronic and vibrational (vibronic) energy levels upon photodynamic processes. The PJT effect may rationalize the photoprotection action and activity of naturally occurring symmetric dyes.
ABSTRACT
The molecular and electronic structure of parent flavone and 49 (poly)methoxylated flavones (P)MFs were studied theoretically. Selected group of flavonoids consists of compounds naturally occurring in citrus plants or synthetic derivatives of flavone. These compounds exhibit several bioactivities in vitro and in vivo and can protect plants from solar ultraviolet (UV) radiation. Substitution induced structural changes in (P)MFs were correlated with published experimental values of P-glycoprotein inhibition effect. We have demonstrated that the C5-C10 bond length of 1-benzopyran-4-one moiety represents a suitable structural descriptor for this bioactivity. Obtained linear equations for the compounds with substituted and non-substituted C3 position enable the prediction of the potential anti-cancer chemo-preventive effect of the rest of studied (P)MFs. Consequently, potentially more effective substances were suggested. Optical properties of (P)MFs and their relationship with the molecular structure was examined in detail for methanol environment, as well. The multiple linear regression model was applied to assess the correlation between experimental absorption and fluorescence wavelengths with the theoretically predicted ones. The UV photo-protective potential of studied derivatives was estimated from the calculated optical properties.
