In vitro antibacterial, anti-biofilm, anti-quorum-sensing, and cytotoxic activities of leaf crude extracts of Cannabis “Gorilla glue 1”

The resilience of biofilms makes it challenging to treat bacterial infections using conventional antibiotics. The study aimed to assess the antibacterial, anti-biofilm, anti-quorum-sensing, and cytotoxic activities of acetone extracts of <i>Cannabis</i> "Gorilla Glue 1" against fish pathogens. Antibacterial activity was determined using the two-fold serial microdilution method, while anti-biofilm activity was assessed using a modified crystal violet staining <i>in vitro</i> assay. Anti-quorum-sensing activity was evaluated via inhibition of violacein production in <i>Chromobacterium violaceum</i> (ATCC 12472). Cytotoxicity was assessed using a colorimetric assay against Vero kidney cells. Solvent extracts from treatment 0.36 g N; 0.12 g P; 0 g K showed the lowest minimum inhibitory concentration (MIC) value (0.02 mg/mL) against <i>Edwardsiella tarda</i> (ATCC 15947) and <i>Pseudomonas fluorescens</i> (ATCC 13525) compared with other treatments. All tested solvent extracts demonstrated the ability to prevent or disrupt biofilm formation; however, treatment 0.36 g N; 0.06 g P; 0.12 g K showed consistent anti-biofilm activity (>50% inhibition) against all tested pathogens. All solvent extract treatments exhibited comparable anti-quorum-sensing activity, while treatment 0.36 g N; 0.06 g P; 0.12 g K demonstrated the highest inhibition of violacein production (98.61% at 1.25 mg/mL). Most solvent extracts were non-cytotoxic to Vero cells, with LC₅₀ values >0.1 mg/mL, except treatment 0 g N; 0.24 g P; 0 g K, which showed high cytotoxicity (LC₅₀ = 0.04 mg/mL). Treatments 0.36 g N; 0.12 g P; 0 g K, 0 g N; 0.36 g P; 0.6 g K, and 0 g N; 0 g P; 0 g K exhibited moderate toxicity (LC₅₀ = 0.06 mg/mL). Treatment 0.36 g N; 0.12 g P; 0 g K displayed the highest selectivity index (3.00) against Vero cells, indicating the most favorable safety profile among the extracts investigated. Leaf extracts of <i>Cannabis</i> exhibited useful bioactivities coupled with low cytotoxicity, providing impetus for further studies on their potential development as protective feed additives against microbial infections in fish production.