Effect of algal antimicrobials on selected aquatic pathogens and characterization of bioactive compounds

Abstract

Marine microalgae have been reported as an excellent source of bioactive compounds. The present study analyzes the existence of bioactive phytochemicals and their efficacy in antimicrobial activity against aquatic pathogens. The antimicrobial compounds were extracted from three marine microalgae, namely Chlorella sp., Pavlova sp., and Chaetoceros sp., and Pavlova sp. showed a broad spectrum of activity. Pavlova sp. extracts were tested against the selected aquatic pathogens, such as Vibrio harveyi, Vibrio parahaemolyticus, Pseudomonas aeroginosa, Aeromonas hydrophila, and Staphylococcus aureus, and the result showed the inhibiting activity against aquatic pathogens. The minimum inhibitory concentration and minimum bactericidal concentration, cytotoxic assay, and mode of action were also studied. The effective five crude extracts were purified by column chromatography and tested against the pathogens; then, the active fraction was partially characterized by Fourier transform infrared (FTIR) analysis. The FTIR result suggested the presence of bioactive groups, such as amines, alkane, carboxylic acid, sulfoxide, alcohol, boron, etc. From the five extracts, two active extracts were selected and subjected to TLC (Thin layer chromatography). The cytotoxic activity (LD-50) indicates that the compound may be safe and effective for clinical trial. Finally, the algal cytotoxic assay concluded that the isolated compound can also be used as an algicide to control algal blooms. This study proves that Pavlova sp. is an excellent source of pharmacologically active resourceful algae and shows effective activity against aquatic pathogens.