August 2020
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The identification of active natural compounds from plants for use as therapeutic agents for aquatic diseases could reduce the use of environmentally harmful chemicals. Lumnitzera littorea is a plant in the Combretaceae family that thrives among mangroves. Although well known in traditional medicine, there are only a few reports of the activity of various parts of this plant against aquatic pathogenic bacteria. Therefore, this work studied the phytochemical composition of the stem-bark, leaf, twig, and flower of L. littorea extracts and further investigated the antioxidant and antibacterial activities. The qualitative and quantitative analyses of phenolic and flavonoid contents were carried using the Folin-Ciocaltue and the colorimetric aluminium chloride methods, respectively. Antioxidant activity was determined by 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and 2,2/-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salts (ABTS) methods. The extracts were screened for antibacterial activity against different pathogens (Streptococcus agalactiae, Aeromonas hydrophila, Vibrio harveyi and V. parahemolyticus) using the hole-plate diffusion method. The results showed the presence of phenolic and flavonoid components in all extracts. Bark and twig extracts had greater total phenolic and flavonoid contents than those from flower and leaf extracts. Significant antioxidant activity was expressed by the bark and twig extracts. All extracts showed a wide range of antibacterial activity against the tested organisms. Bioactive substances present in L. littorea extracts exhibited antioxidant and antibacterial activities. L. littorea could be a potential source of natural bioactive compounds that could be used to develop safe and environmentally friendly pharmaceuticals against bacterial pathogens in aquatic animals.
