Antibacterial Effects of Terminalia arjuna (Roxb.) Leaf and Curcuma longa (L.) Bulb Extracts on the Fish pathogen Acinetobacter rudis

Abstract

Studies were conducted to determine the antibacterial effects of arjun, Terminala arjuna (Roxb.) leaf and turmeric, Curcuma longa (L.) bulb extracts against pathogenic Acinetobacter rudis infection in pangas, Pangasianodon hypophthalmus and rohu, Labeo rohita. The arjun leaf and turmeric bulb were collected from the adjacent area of Bangladesh Agricultural University (BAU), Mymensingh, dried and powdered finely using an automated grinder. Laboratory stocked fish pathogen A. rudis, isolated previously from the body lesions of pangas, was used for challenge test. Biosafety test was performed by aqueous extracts of arjun leaf and turmeric bulb to determine the tolerance of fish. Pangas (7.194±1.09 g) and rohu (3.46±1.12 g) both could tolerate 120 ppm dip bath of arjun extracts. In case the of turmeric extract, pangas tolerated 120 ppm but rohu could tolerate upto 90 ppm. An immersion challenge test with 70 P. hypopthalmas and 70 L. rohita was performed in laboratory using A. rudis with pre-fixed doses of 4.07×106 and 4.07×107 CFU/mL. After the experimental infection, aqueous extract of turmeric was found to have distinguished effects where 87.5% of infected fish were recovered with prolonged immersion treatment. Water extracts of arjun leaf exhibited 67.5% survival of fish. In-vitro test by acetone extracts of both arjun and turmeric showed inhibition zones against A. rudis at different dosage in comparison with frequently used antibiotics. Maximum inhibition zone was 7 mm at 125 µL of the acetone extract of arjun while turmeric extract showed 5 mm at the same concentration against A. rudis. Thin layer chromatography confirmed the presence of at least one component in the acetone extracts which might be responsible for the antibacterial activity. This preliminary investigation revealed the potential antibacterial effects of T. arjuna leaf and C. longa bulb extracts against A. rudis infection in fish and can be suggested for further detailed studies to establish these medicinal plants for alternative fish health management.