Screening of antioxidant activity, antimicrobial properties, and chemical profiles of 31 plant species against Vibrio and Pseudomonas in the Ecuadorian shrimp industry

Opportunistic pathogens represent a significant threat to shrimp aquaculture, as they can reduce productivity and cause substantial economic losses. Plant-derived compounds have been investigated as potential alternatives for controlling bacterial infections associated with shrimp farming. In this study, a bioprospecting screening of 31 plant species collected from the localities of Taura and Sangolquí (Ecuador) was conducted to evaluate their antioxidant and antibacterial activities against bacterial species associated with aquaculture systems. Among the evaluated extracts, Eucalyptus globulus Labill. and Psidium guajava L. leaves exhibited notable bioactive potential and were selected for further analysis. The antioxidant activity of the extracts was assessed using ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. Antibacterial activity was evaluated using disk diffusion and microdilution methods. In addition, fractions from the most active extracts were analyzed using HPLC-DAD-MS/MS to explore their chemical composition and potential association with antibiofilm activity. The results showed that Eucalyptus globulus and Psidium guajava leaf extracts exhibited minimum inhibitory concentration (MIC) values ranging from 250 to 20,000 μg/mL against the tested Vibrio species and P. aeruginosa strains, with Eucalyptus extracts generally showing lower MIC values and a more consistent inhibitory profile across extraction solvents. Antioxidant activity was also observed in methanolic extracts. Fraction F5 of the Eucalyptus leaf extract reduced biofilm biomass by up to 76.09% and viable cells by 70.15%. For Psidium guajava leaves, fractions F1 (61.98%–71.69%), F4 (55.14%–70.02%), and F6 (38.84%–65.88%) showed the highest antibiofilm activity, particularly against mature biofilms associated with Vibrio spp., while limited activity was observed against Pseudomonas aeruginosa. HPLC-DAD-MS/MS analysis tentatively identified several metabolites belonging to the flavonoid group in the most active fractions. Overall, the results suggest that extracts from Eucalyptus globulus and Psidium guajava leaves possess antioxidant and antibacterial activities that may represent promising candidates for further investigation as plant-derived antimicrobial agents for aquaculture systems. However, additional studies, including in vivo validation, toxicity assessment, and formulation development, are required before practical application.