Browsing by Author "Piyadasa, H.T.N.I."

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    Antibacterial Efficacy of Mangrove Rhizophora mucronata Extracts on Aquatic Bacterial Pathogens
    (Uva Wellassa University of Sri Lanka, 2013) Bokalawella, S.H.K.; De Silva, D.P.N.; Jayamanne, S.C.; Gunasekara, A. J. M.; Piyadasa, H.T.N.I.
    Medicinal plants contain components of therapeutic value and are used as remedies for human/animal diseases. They are environmentally friendly due to less toxicity and have minimal health hazards (Opara and Wokocha, 2008). Mangrove plant extracts and its major chemical classes displayed various levels of antibacterial, antifungal, antifouling, antiviral and free radical scavenging effects due to their bioactive compounds (Bandaranayake, 2002). Bacterial infections cause severe economic losses to the aquaculture industry which increased the use of antimicrobial agents significantly as a treatment (Alderman and Michel, 1992). Improper usage and presence of drug residues lead to the development of resistant strains of pathogenic bacteria. Therefore, novel antibacterial compounds of natural products which degrade easily need to be synthesized to overcome above consequences. Aim of this study was to find out the antibacterial efficacy of Mangrove Rhizophora mucronata extracts on aquatic bacterial pathogens, to be used as a remedy to treat fish diseases. Methodology Fresh matured leaves of six mangrove plant species (Avicennia marina, Lumnitzera racemosa, Bruguiera sexangula, Acanthus ilicifolius, Excoecaria agallocha and Rhizophora mucronata) were collected from mangrove reserve at Kadolkele, Negombo and were brought to the laboratory for making extractions. Initially, preliminary trials were conducted for identification of most suitable species with antibacterial properties against four aquatic pathogens Listeria monocytogenes) in vitro by well diffusion method. Upon identification of Rhizophora mucronata having the highest inhibitory zone for tested bacteria, further analysis were performed using various parts such as roots, barks, flowers and fruits of R. mucronata. The solvent was extracted by mixing 8 g of each part of mangrove in powder form, with 125 ml of 95% methanol and evaporating methanol using rotary flash evaporator (model 519-00000-00- 3). Antibacterial efficacy was assessed against all four species of fish pathogens, using was used as the positive control against Rhizophora mucronata extractions of 350 mgml each. After 24 hour incubation at 25 o C, the diameters of the inhibitory zones were obtained and statistically analyzed by using One way-ANOVA incorporated in Minitab version 16. Results and Discussion All six mangrove species showed antibacterial activity against Listeria monocytogenes, Pseudomonas fluorescens, and Pseudomonas aeruginosa significantly (p<0.05) but insignificant for Shigella flexneri (p>0.05). Highest inhibition zones were observed in Rhizophora mucronata leaf extract against all bacteria examined for the study (Table 1). Rhizophora mucronata extracts (root, bark, fruit and flower) also exhibited positive inhibition zones for all the tested bacterial species cultured in vitro. Root and bark extracts possessed higher antibacterial potential when compared to the fruit and flower extracts. Rhizophora leaf extracts showed highest inhibition for Listeria monocytogenes and Pseudomonas fluorescens while root and bark extracts were effective against Shigella flexneri and Pseudomonas aeruginosa respectively (Figure 1). The overall mean comparative evaluation on antibacterial efficacy of Rhizophora mucronata extracts displayed the highest in leaves followed by the root, bark and fruit extracts. The minimum antibacterial activity was observed in the flower extracts.