Synthesis and in vitro antimicrobial activity of metal complexes with flavonoids

YAINI A. VITTI APDELGANI; LUCÍA B. SAUTÚ; JAVIER L. RODRÍGUEZ; AILÉN N. RODRÍGUEZ; JUAN J. MARTÍNEZ MEDINA; LIBERTAD L. LÓPEZ TÉVEZ

Rosario, Santa Fe

Congreso; 4ta Reunión Internacional de Ciencias Farmacéuticas; 2016

Universidad Nacional de Rosario

The enormous importance of developing novel antimicrobial drugs for the treatment of infectious diseases lies in the increasing development of resistant microbial strains. The aims of this study were to synthetize and evaluate the antimicrobial activity of two complexes previously reported (Cu-Chrysin and Zn-Silibinin). The antimicrobial profile of the metals, the ligands and the complexes have been studied against five bacterial strains (Escherichia coli ATCC 35218, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923 and Enterococcus faecalis ATCC 29212), and seven fungal strains (Candida parapsilosis ATCC 22019, Candida albicans ATCC 10231, and clinical isolates of Candida tropicalis, Candida krusei, Candida glabrata, Candida parapsilosis and Candida albicans) by the agar dilution method. After preparation and sterilization of serial two-fold dilutions of the tested compounds, 0.5 mL of each dilution were added to 4.5 mL of melted Mueller Hinton Agar (MHA) and poured into a Petri dish. The final concentrations ranging in the MHA were from 1.46 to 1500 µg/mL. After cooling and drying, the agar surface was inoculated with 2 µL of the microbial suspensions (~108 UFC mL-1) and incubated aerobically at 37 °C for 18 and 48 h for bacteria and fungi, respectively. After incubation, the minimum inhibitory concentration (MIC) was interpreted and the inhibition of microbial growth was judged by comparison with growth in control plates (without antimicrobial agent). After the synthesis, the complex formation was confirmed by infrared spectroscopy. The results indicate that the ligand Silibinin and the Zn-Silibinin complex exert relevant activity against Gram-positive bacterial strains. For the Staphylococcus strains, the Zn-Silibinin complex (MICs ≤ 188 µg/mL) show higher activity than Silibinin (MICs ≤ 375 µg/mL). The Cu-Chrysin complex shows no antimicrobial activity (MICs > 1500 µg/mL). The fungal strains were resistant to all compounds. In conclusion, the complexation of Silibinin with zinc enhances their antibacterial activity.