Screening of marine algae (Padina sp.) from the Lengeh Port, Persian Gulf for antibacterial and antifungal activities

Objective: To evaluate the antibacterial efficacy of different solvent extracts of Padina sp. against selected human pathogenic bacteria and fungi species such as Escherichia coli, Shigella sp., Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa, Aspergillus flavus and Candida albicans. Methods: Various solvents including methanol, ethyl acetate, chloroform and hexane were used to acquire crude extracts from marine algae Padina sp. After crude preparation, antibacterial and antifungal activities were screened against clinically important human pathogenic bacteria using disc and well diffusion methods. For all the bacterial species used in this research, minimum inhibitory concentration was undertaken considering various solvent extracts of Padina sp. To ensure the accuracy of experiments, a positive control was also included. Results: Confirmed that hexane is the best solvent to extract antimicrobial agents from Padina sp. Among selected bacteria, S. aureus was the most sensitive test microorganism. While, all other microorganisms showed resistance against methanol, ethyl acetate, chloroform extracts. In fact, by increasing concentration of hexane extract, inhibition of S. aureus growth or antimicrobial activity was increased. Growth inhibition zone in well method showed better results compared to disc diffusion method. The minimum inhibitory concentration and minimum bactericidal concentration of hexane extract were 15 and 30 mg/mL against S. aureus, respectively. All Padina sp. extracts did not reveal any antifungal activities against fungi species in this study. Conclusions: Brown algae extracts showed sufficient antibacterial properties against S. aureus. Therefore, Padina sp. in this research can be a good candidate to design and manufacture novel antibacterial agents used in pharmaceutical industries.