Therapeutic effects of mango (Mangifera indica) and cashew (Anacardium occidentale) leaves extracts against certain pathogenic bacterial strains from Clarias gariepinus

Abstract

The study was carried out to evaluate the potential therapeutic effects of mango (Mangifera indica) and cashew (Anacardium occidentale) leaves extracts against nine fish pathogens: Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Bacillus substillis, Samonella typhi, Staphylococcus epidermis, Streptococcus iniae, Aeromonas hydrophila and Aspergillus niger using pour plate method. Phytochemical screening and minimum inhibitory concentration of ethanolic and methanolic extracts of mango and cashew leaves were determined using standard methods. Data were analyzed using ANOVA at P = 0.05. The results of antimicrobial properties revealed that both plants extracts showed antimicrobial properties. However, ethanolic and methanolic extracts of mango leaves exhibited the highest antimicrobial activities against all the pathogens investigated. No antimicrobial properties were recorded in the negative control (distilled water) and no antimicrobial activities were recorded for Streptococcus iniae and Aspergillus niger in erythromycin (50 mg/ml and 100 mg/ml) which serve as the positive control. The phytochemical screening for metabolites indicated the presence of saponins, alkaloids, tannins, glycosides, phenols and protein while flavonoids and steroids were not detected in both plants. The minimum inhibitory concentration of methanolic extracts of mango and cashew leaves is 1000 µg/ml and minimum inhibitory concentration of ethanolic extracts of mango and cashew leaves is 500 µg/ml. The results indicate the possibility of using mango and cashew leaves extracts in the treatment of microbial infections in fishes.

Keywords: Fish diseases, Mangifera indica, Anacardium occidentale, Antimicrobial, Phytochemical screening