SPECTROSCOPY AND ANTIMICROBIAL ANALYSIS

SILVERO J; GARCIA F; PAEZ P. L.; BECERRA M C; SHARMA R; SINGH A; ARGUELLO GA

Carlos Paz

Congreso; XVIII Simposio Nacional de Química Orgánica (XVIII SINAQO),; 2011

SPECTROSCOPY AND ANTIMICROBIAL ANALYSIS OF SOME Co(III) COMPLEXES M. Jazmín Silvero,* P. Facundo García,* Paulina Páez,* M. Cecilia Becerra,*                    Ajnesh Singh,** Raj Pal Sharma** y Gerardo A. Argüello* * INFIQC, Departamento de Fisicoquímica, FCQ, UNC, Córdoba, 5000, Argentina, jsilvero@fcq.unc.edu.ar       ** Department of Chemistry, Panjab University, Chandigarh, 160014, India The Photodynamic Therapy (PDT) has emerged as an attractive option for the treatment of cancer pathologies[i] thanks to the study and utilization of transition metal complexes (among other) as photosensitizers.[ii] This complexes use to photochemically generate in situ toxic species, which are highly reactive. The Photodynamic Antimicrobial Chemotherapy (PACT) follows the general principles of PDT. Recent literature reports indicate that PACT is a very promising treatment against important clinical pathogens. [iii] The aim of this work was to study new cobalt complexes as possible photosensitizers to be used in PDT and PACT. The complexes [Co(phen)(H2biim)2](BF4).2H2O, (1); [Co(phen)2(Hbiim)]Cl2.10H2O, (2) and [Co(H2biim)3](NO3)3, (3) were synthesized for Dr. R.P. Sharma et al. and characterized for our group. Absorption spectra were recorder in MQ water and PBS (phosphate buffer solution) pH 7.4 and the extinction coefficients of the three complexes were calculated for its absorption peaks in the UV, for lasers and diode emission lines (337, 355 and 457 nm). The molar extinction coefficients at 271, 337, 355 and 457 nm for complex (1) are 30848, 912, 489 and 103 cm-1M-1; for complex (2) are 168512, 4348, 2070, 118 cm-1M-1 respectively; and for complex (3) the coefficients at 295, 337, 355 and 457 nm are 27248, 3057, 2729, 1311 cm-1M-1. On the other hand, to conduct microbiological test, the stability of complexes solutions was evaluate recording systematically the UV-vis spectra through 24 h at room (20 ºC) and body temperature  (37 ºC). The solutions show stability within the 24 h of the study. The antimicrobial activity of complexes (1), (2) and (3) were tested against Staphylococcus aureus (ATCC 29213) (Gram positive) and Escherichia coli (ATCC 25922) (Gram negative) through the determination of the MIC in duplicated. [iv] Complex (3) was not stable enough and precipitated in the culture media. The MIC values for (1) and (2) were too high to be used without consider any collateral damage in the living organism. Besides, they would need to be even higher to rich an acceptable absorbance at visible wavelengths, which is the section of the spectra which could be used in PDT. These results show very little potential of these complexes as photosensitizers. [i] - Robertson CA, Evans DH, Abrahamse H. J Photochem Photobiol B. 2009 Jul 17;96(1):1-8. Epub 2009 Apr 11. Review. [ii] - Boca SC, Four M, Bonne A, van der Sanden B, Astilean S, Baldeck PL, Lemercier G. Chem Commun (Camb). 2009 Aug 14;(30):4590-2. Epub 2009 Jun 17. [iii]  - Jori G, Fabris C, Soncin M, Ferro S, Coppellotti O, Dei D, Fantetti L, Chiti G, Roncucci G. Lasers Surg Med. 2006 Jun;38(5):468-81. Review [iv] - Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically; Approved Standard - Seventh Edition. CSLI document M7-A7. Clinical and Laboratory Standards Institute, Wayne, Pennsylvania, USA, 2006.