Integrated Phytochemical and Bioactivity Evaluation of Ocimum tenuiflorum Linn. Essential Oil Against Multidrug-Resistant Aeromonas spp.

Plant essential oils extracted from various parts are known for their potential antimicrobial properties. The gas chromatography and mass spectrometry (GC-MS) of Ocimum tenuiflorum essential oil (TEO) revealed estragole and eugenol as major compounds. The FTIR profiling showed the presence of functional groups like O─H, C─H, C═O, C─C, which is in correspondence with the results of GC-MS analysis. In a similar way, UV-visible spectroscopy identified peaks within 315 nm that showed the presence of C═C and aromatic compounds. The disc diffusion results revealed Aeromonas hydrophila to be more sensitive, with 29.57 ± 0.32 mm zone of inhibition (ZoI) and Aeromonas jandaei with 28.07 ± 0.83 mm. The MIC and MBC values of A. hydrophila were 0.125% and 0.25%, while 0.25% and 0.5% for A. jandaei. DPPH and ABTS assay for antioxidant activity determined the IC₅₀ value to be 53.67 ± 0.16 µg/mL and 53.7 ± 0.2 µg/mL. Strong antibiofilm activity (%) was observed against both A. hydrophila and A. jandaei, with 94.3% and 90% respectively. The present study provides insight into the sustainable use of TEO against bacterial infections by Aeromonas spp. isolated from moribund Labeo rohita.