Antibacterial potential of Carica papaya, Persea americana and Azadirachta indica extracts against aquatic pathogens
Abstract
Phytochemical screening of the dried leaves of papaya (Carica papaya), avocado (Persea americana) and neem tree (Azadirachta indica) revealed the presence of bioactive anthraquinones, tannins, flavonoids, and saponins, which have been linked to their antibacterial properties. Antibacterial activity of the aqueous and ethanolic extracts of plant materials were tested by disk diffusion method against Pseudomonas aeruginosa, Streptococcus faecalis, Staphylococcus aureus, and Aeromonas hydrophila. All pure extracts displayed specific activity in growth of inhibition of all bacteria tested at a concentration of 0.1–1 mg/mL. Antibiotic oxytetracycline (30 μg) was used as positive control while the respective solvents were used as negative controls. Results showed that ethanolic extracts were more active compared to aqueous extracts (p < 0.05) and growth of inhibition also decreased with decreasing concentration. In the 96 h acute toxicity test, plant extracts used in this study manifested toxic effect in varying degree to both Nile tilapia (Oreochromis niloticus) and milkfish (Chanos chanos) fry. Leaf extracts of A. indica were the most toxic to both fish. However, treatment concentrations against bacteria were much lower than the lethal concentrations. This study suggests that dried leaves of papaya, avocado and neem tree has the potential to control fish diseases caused by bacteria.
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