RESUMEN

Compounds having antimicrobial activity were synthesized from sodium alginate, the main constituent of brown algae. Sodium alginate was oxidized with sodium periodate to get alginate dialdehyde (ADA). FTIR spectrum of the ADA gave very small peak characteristic for aldehyde groups at 1720 cm-1, indicating that the aldehyde group is masked somehow. It may be hydrated, involving at hemiacetal formation or hemialdol, similar to cellulose dialdehyde. Two methods were used for the condensation of ADA with o-phenylenediamine analogs to obtain the final products. The first method was stirring at room temperature and the second method was heating in microwave. The microwave method gave higher yield and shorter reaction time than the other method. The condensation reaction is considered as a shiff-base formation and the proposed mechanism was suggested. The condensation products were characterized by FTIR and UV spectra. The antimicrobial potency for five of these products in addition to the used alginate and to the precursor amines was evaluated against four pathogenic fungi and six pathogenic bacteria species.

Asunto(s)

Alginatos/farmacología , Antibacterianos/farmacología , Antifúngicos/farmacología , Hongos/efectos de los fármacos , Bacterias Gramnegativas/efectos de los fármacos , Alginatos/síntesis química , Alginatos/química , Antibacterianos/síntesis química , Antibacterianos/química , Antifúngicos/síntesis química , Antifúngicos/química , Conformación de Carbohidratos , Relación Dosis-Respuesta a Droga , Pruebas de Sensibilidad Microbiana , Microondas , Relación Estructura-Actividad

RESUMEN

A new Zn-N4 -Schiff base L=((±)-trans-N,N'-Bis(2-aminobenzylidene)-1,2-diaminocyclohexane) complex was synthesized and fully characterized, showing an unexpected self-assembled double-stranded helicate structure. The X-ray crystal analysis of the Zn2 L2 complex ((C40 H44 N8 Zn2 ,CH2 Cl2 , a=14.2375(3) Å, b=16.7976(4) Å, c=16.1613(4) Å, monoclinic, P21 /n, Z=4) shows a centrosymmetrical structure in which zinc atoms are in distorted tetrahedral environments, revealing an M- (R, R) left-handed helicity in its asymmetric unit. However, it was observed that this dinuclear complex is thermodynamically unstable in the presence of small water amounts and undergoes demetallation into free N4-Schiff base ligand and ZnO nanoparticles. This hydrolysis process was thoroughly identified and monitored through detailed 1 H NMR, DOSY NMR analysis. The reaction mechanism of this demetallation event was elucidated by using the DFT method, involving an activation energy smaller than 13 kcal/mol. Besides, a theoretical mechanism of the demetallation process is given for the first time.