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Infections by multiresistant microorganisms have led to a continuous investigation of substances acting as modifiers of this resistance. By following this approach, the chemical composition of the essential oil from Piper caldense leaf and its antimicrobial potential were investigated. The antimicrobial activity was determined by broth microdilution method providing values for minimum inhibitory concentration (MIC), IC50, and minimum fungicidal concentration (MFC). The essential oil was tested as a modulator for several antibiotics, and its effect on the morphology of Candida albicans (CA) strains was also investigated. The chemical characterization revealed an oil composed mainly of sesquiterpenes. Among them are caryophyllene oxide (13.9%), spathulenol (9.1%), &delta, cadinene (7.6%) and bicyclogermacrene (6.7%) with the highest concentrations. The essential oil showed very low activity against the strains of CA with the lowest values for IC50 and MFC of 1790 &mu, g/mL and 8192 &mu, g/mL, respectively. The essential oil modulated the activity of fluconazole against CA URM 4387 strain, which was demonstrated by the lower IC50 obtained, 2.7 &mu, g/mL, whereas fluconazole itself presented an IC50 of 7.76 &mu, g/mL. No modulating effect was observed in the MFC bioassays. The effect on fungal morphology was observed for both CA INCQS 40006 and URM 4387 strains. The hyphae projection was completely inhibited at 4096 &mu, g/mL and 2048 &mu, g/mL, respectively. Thus, the oil has potential as an adjuvant in antimicrobial formulations.

Two 1,8-naphthyridines were synthesized and found to be fluorescent in solution. These compounds were studied in the presence of Cu + and Cu 2+ ions and it was verified that the metal causes the quenching of their fluo- rescence emission, due to the formation of complexes be- tween the naphthyridine and the metal. A displacement assay was carried out in a DMSO-water mixture with the addition of various anions to the solutions of the complexes, and it was observed that these systems have a high capacity to selectively detect cyanide.

The influence of the bridging group between the mesogenic group and the terminal position on liquid-crystalline behavior was investigated. Two liquid-crystalline series containing pentagonal heterocycles were synthesized for this purpose. The liquid-crystal phase of mesogens with the isoxazole group was more stable than that of those with isoxazole and tetrazole groups in the same molecule. The mesogens with only the isoxazole group showed better thermal properties than those with isoxazoles and tetrazoles. Nematic and smectic phases were observed. The mesophase sequences of the materials were investigated by polarization microscopy and DSC (Differential Scanning Calorimetry).

Homologues series of some derivatives of 3,5-(4-substituted phenyl)-1,2,4-oxydiazole were synthesized and their phase behavior studied. Introduction of the pentagonal heteroaromatic ring leads to significant changes in mesomorphic behavior in comparison with analogous compounds containing the phenyl ring. The synthesised compounds exhibit smectic and nematic phases.

The title compound, C 7 H 6 N 4 O.1.5H 2 O, is a key intermediate in the synthesis of mesogens, which are derivatives of phenyltetrazole. The tetrazole and phenyl rings are planar to within 0.007 (2) A, with a dihedral angle of 14.8 (1)° between the planes.