Antimicrobial potential of padina australis and sargassum polycystum against respiratory infections causing bacteria

Discovery of the new drug from marine natural products is of researcher's interest to address the rapid development of antibacterial resistance. Seaweeds are marine algae that contain a variety of bioactive compounds with great potential of antimicrobial activity. Brown seaweeds Sargassum polycystum and Padina australis (Phaeophyta) were collected from Port Dickson, cleaned, freeze-dried, ground, macerated with 80% ethanol, evaporated using rotary evaporator and stored at-20°C. The seaweed extracts were examined for its phytochemical content and antibacterial activity against Streptococcus pneumoniae and Klebsiella pneumoniae. The presence of saponins, steroids and cardiac glycosides were observed in S. polycystum extract, whereas steroids and cardiac glycosides were observed in P. australis extract. In the disk diffusion assay against S. pneumoniae, at 25 mg/mL, P. australis extract has showed larger inhibition zone (8.80 ± 1.12 mm) as compared to S. polycystum extract (6.70 ± 0.24 mm). P. australis extract has showed MIC and MBC values at 6.25 mg/mL against S. pneumonia. P. australis extract had better antibacterial activity towards Gram-positive S. pneumoniae, as compared to S. polycystum extract. Further studies on identification of bioactive antibacterial compounds in P. australis extract and toxicity test will be carried out.