Pharmaceutical Innovations for Sustainable Healthcare

Comparative In Vitro Antibacterial Evaluation of Zinc(II) and Copper(II) Salts and Their Valproate Complexes Against Ciprofloxacin-Resistant Escherichia coli

Not scheduled

20m

كلية الصيدلة

Podium Presentation Pharmaceutical Chemistry and drug design

Speaker

Gheith. M Al-asadi (University of Alameed college of Pharmacy)

Abstract

Background:
The increasing prevalence of antibiotic-resistant bacteria has intensified the search for alternative antimicrobial agents. Metal-based compounds and their complexes have attracted interest as potential antibacterial agents, particularly against strains resistant to conventional antibiotics.
Objective:
This study aimed to synthesize zinc(II) and copper(II) valproate complexes, characterize the obtained products, and evaluate their antibacterial activity against ten clinical isolates of ciprofloxacin-resistant Escherichia coli.
Method:
The complexes were prepared by in situ formation of sodium valproate followed by reaction with ZnCl₂ at pH 7.0–7.5 or Cu(NO₃)₂·3H₂O at pH 6.0–7.0. The precipitated products were isolated, washed, dried, and characterized by FT-IR spectroscopy and melting/decomposition behavior. Antibacterial activity was assessed by agar well diffusion on Mueller–Hinton agar at 500, 250, and 125 µg/mL. Ciprofloxacin and 5% DMSO served as controls.
Results:
FT-IR changes supported coordination of valproate through the carboxylate group. The free valproic acid C=O band at approximately 1707 cm⁻¹ disappeared in the Zn(II)- and Cu(II)-valproate spectra, while carboxylate-related bands appeared within 1624–1418 cm⁻¹, supporting deprotonation and metal interaction. The exact coordination mode could not be conclusively assigned from FT-IR alone. Ciprofloxacin and 5% DMSO produced no inhibition zones. In contrast, the tested compounds showed measurable activity. ZnCl₂ produced the largest inhibition zones: 19.99 ± 0.47, 19.44 ± 0.44, and 19.04 ± 0.17 mm at 500, 250, and 125 µg/mL, respectively. Zn(II)–valproate remained active but showed lower inhibition than ZnCl₂. Cu(II)–valproate showed slightly larger inhibition zones than Cu(NO₃)₂; at 500 µg/mL, values were 15.12 ± 0.36 and 14.36 ± 0.24 mm, respectively. Overall activity followed: ZnCl₂ > Zn–valproate > valproic acid ≈ Cu–valproate > Cu(NO₃)₂.
Conclusion:
Valproate complexation modified the antibacterial behavior of Zn(II) and Cu(II) differently. Zinc was more active as the free salt, whereas Cu(II)–valproate showed slightly larger inhibition zones than the corresponding copper salt. Further MIC/MBC assays, structural characterization, and mechanistic studies are recommended.