TLC Bioautographic Detection and Characterization of Antibacterial Compound from the Cyanobacterium Anabaena oryzae

Background: Microalgae have the potential to produce natural bioactive compounds, which are difficult to be produced by chemical synthesis. These compounds also possess diverse biological activities, such as antibacterial, anti-inflammatory, anti-atherosclerotic and anti-carcinogenic activities.

Objective: The purposes of the current study were to use a simple and accurate Thin layer chromatography (TLC) bioautographic method for detection and isolation of antibacterial compound from the complex cyanobacterial extract and the characterization of the isolated compound.

Materials and Methods: Polar and non-polar extracts of cyanobacterium Anabaena oryzae were screened for antibacterial activity against various Gram-positive and Gram-negative bacterial species using agar well diffusion method. The mode of action of methanolic extract on pathogenic bacteria was examined using scanning electron microscopy, Thin layer chromatography-direct bioautography (TLC-DB) was applied for the first time in detection and isolation of the antimicrobial compound in cyanobacterial extract. The target band was purified by silica gel column chromatography and antibacterial compound was isolated. The isolated compound was characterized using IR and mass spectroscopy.

Results: The methanolic extract had the highest biological activity against Escherichia coli, MIC 0.05 µg/ml. Scanning electron microscopy revealed a shortening and swelling of the E. coli cells, and multiple blisters and bubbles formed on their surface. One compound with antibacterial activity was isolated using (TLC-BD) and column chromatography. Infrared spectra (IR) indicated that the isolated compound was phenolic compound. Mass spectroscopy indicated that its molecular weight was 443.38.

Conclusion: It was concluded that cyanobacteria Anabaena oryzae are metabolically very diverse group and a promising group of organisms for research on medicines discovery. It was also concluded that (TLC-DB) is very useful in the isolation and identification of compounds with antimicrobial activity from biological extract.