Potential of Thiocolchicoside as an Antimicrobial Repurposing Agent: An In Vitro Study

Antimicrobial resistance (AMR) is a global health emergency that poses a hazard to the effective management of infectious diseases. Drug repurposing provides a cost-effective and expeditious solution by identifying new applications for existing pharmaceuticals. A semi-synthetic derivative of colchicoside, thiocolchicoside (THC), has been recently investigated for its potential anticancer and antimicrobial properties. It is prescribed as a muscle relaxant. THC was tested against a variety of gram-positive and gram-negative bacteria, as well as fungal isolates, at concentrations ranging from 4000 to 62.5 µg/mL. Standard antibacterial and antifungal controls were provided by gentamicin (GN) and fluconazole (FZ). Turbidity and absorbance-based assays at 600 nm were employed to ascertain the minimum inhibitory concentrations (MICs). THC demonstrated MICs of 125 µg/mL against Streptococcus mutans, Staphylococcus aureus, Lactobacillus acidophilus, Escherichia coli, and Candida albicans. The moderate antimicrobial activity with variable potency was indicated by the higher MICs for Pseudomonas aeruginosa (1000 µg/mL), Proteus mirabilis (1000 µg/mL), Klebsiella pneumoniae (500 µg/mL), and Aspergillus niger (250 µg/mL). Particularly for Aspergillus niger, fungal inhibition necessitated elevated dosages. The results were presented as the mean ± standard deviation, and all experiments were conducted in triplicate. Statistically significant differences (p < 0.05) were identified in the MIC values of THC compared to standard drugs GN and FZ across identical microbiological strains utilizing paired t-tests. THC exhibited lower activity compared to GN and FZ, yet it showed initial promise as an adjunct antimicrobial agent; nonetheless, this assessment is tentative due to the comparatively elevated MIC values and the constraints of in vitro data lacking mechanistic or in vivo corroboration. In order to improve its therapeutic profile, additional mechanistic studies, synergistic evaluations, and nanotechnology-based formulations are necessary.