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The molecular structure of 1:1 complex formed between the naturally occurring polyether ionophore, called lasalocid acid (LAS) and propargylamine (PROP) is studied by X-ray, FT-IR, (1)H NMR, (13)C NMR and ESI-MS methods. The complex formed between deprotonated LAS acid and protonated PROP molecule is stabilized by intra- and inter-molecular hydrogen bonds. The protons of the protonated amine group are hydrogen bonded to etheric and hydroxyl oxygen atoms of the LAS anion. The similarity of the FT-IR spectra of the LAS-PROP complex in solid state and in solution demonstrated that the molecular structures of the complex in both states are comparable. It is shown that LAS in solution can form concurrent complexes with metal cations (M=Li(+), Na(+), K(+)) and amine existing in equilibrium. Analysis of the structures of lasalocid complexes is important for a better understanding of the antibacterial and anticancer properties of lasalocid acid., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Monensin A phenylurethane sodium salt (MON-UR1-Na) crystals were studied by the X-ray, NMR, FT-IR and PM5 semi-empirical methods. The X-ray data show that the compound forms a pseudocyclic structure, stabilized by three intramolecular hydrogen bonds, and the sodium cation coordinated by five oxygen atoms in the hydrophilic sphere. The NMR and FT-IR data demonstrate that this pseudocyclic structure is also conserved in CH(2)Cl(2) solution. This structure of MON-UR1-Na is significantly different than the ones previously proposed by Westley et al. and Tanaka et al. The semi-empirical calculations of the MON-UR1-Na structures indicate that the one of the crystal is the most energetically favorable one. Other parameters, such as the size, chemical and biological nature of the urethane substituent, and especially the free carbonyl urethane group, may have a role in the biological activity of MON-UR1-Na. The in vitro microbiological tests provide evidence that MON-UR1-Na shows higher antibacterial activity against human pathogenic bacteria, including antibiotic-resistant Staphylococcus aureus and Staphylococcus epidermidis than the parent unmodified antibiotic-Monensin A.

Using Gossypol (GOS) extracted from cotton seeds, a series of its Schiff bases (1-18) and hydrazones (19-27) have been synthesized and evaluated for their antimicrobial activities against Gram-positive bacteria, Gram-negative bacteria and yeast-like organisms. Of the 27 aza-derivatives of gossypol, 11 have been found active against the microorganisms tested, similar to gossypol. Crystal structures of the new Schiff base (compound 7) and hydrazone (compound 25) of gossypol reveal the presence of two different tautomers within two types of the aza-derivatives studied. The newly synthesized aza-derivatives of gossypol are characterized by the FT-IR, NMR and MS methods.