Evaluation of antibacterial and antioxidant potentials of epidermal mucus of Clarias batrachus L. from freshwater bodies of India and its biochemical characterisation

Abstract

The epidermal mucus of fish serves as a vital line of defence against pathogens and oxidative stressors in aquatic environments. In this study, we evaluated the antibacterial and antioxidant properties of the epidermal mucus of Clarias batrachus L., commonly known as the walking catfish, sourced from freshwater bodies in India. The mucus samples were collected and assessed for their efficacy against a panel of pathogenic bacterial strains, including Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Escherichia coli. This was done using the agar cup/well diffusion method, along with determination of Minimum Inhibitory Concentration (MIC). The results of the MIC assay showed that E. coli and S. aureus exhibited greater susceptibility to the 50 μg ml⁻¹ mucus sample compared to B. subtilis and P. aeruginosa. The antioxidant capacity of the mucus was assessed through DPPH scavenging activity, demonstrating notable antioxidant potential. Furthermore, biochemical characterisation of the mucus was conducted using gas chromatographymass spectrometry (GC-MS), which identified several bioactive compounds, including cyclotrisiloxane (hexamethyl), cyclotetrasiloxane (octamethyl), cyclopentasiloxane (decamethyl), naphthalene, phenol, 3,5-bis(1,1-dimethylethyl), and hexadecanoic acid methyl ester. Based on the available reviews, these bioactive compounds are recognised for their antimicrobial and antioxidant properties. These findings also highlight the diverse protective functions of C. batrachus epidermal mucus, acting both as a barrier against bacterial pathogens and a natural source of antioxidants. Overall, this study provides valuable insights into the potential biomedical applications of C. batrachus epidermal mucus and lays the groundwork for further research in this field. This research is particularly applicable in Africa given the prevalence of Clarius spp. in Africa, which may exhibit the same physiological features as C. batrachus.