The investigation of anti-bacterial activity of methanolic extract of brown algae (Padina gymnospora) against some gram negative bacteria

Nowadays due to the emergence of resistant forms of pathogenic bacteria, discovering new antimicrobial substances from marine natural resources is considered very important. This study aims to investigate the antibacterial activity of methanolic extract of brown algae against some Gram negative bacteria. After sampling and transferring the samples to the laboratory, algae samples were washed, dried and pulverized; then, the extraction was conducted using methanol solvent. Methanolic extracts of algae (padina gymnospora) were prepared in four concentrations of 10 to 80 mg/ml and were tested against 4 strains of Gram negative bacteria Vibrio cholerae, Morganella morganii, Proteus mirabilis and Proteus vulgaris using disc diffusion technique and inhibition growth zone measurement. The results revealed that P. vulgaris, with growth inhibition zone diameter of 11.23±0.25 mm in 80 mg/ml concentration, showed the maximum sensitivity to algae extract. This value had a significant difference compared to reference antibiotics of gentamycin and neomycin and all other concentrations (p<0.05). However, in 10 and 20 mg/ml concentration of algae extract, there was not seen any significant effect on tested bacteria. In vitro serial dilution results showed that MIC and MBC were 0.8 mg/ml. Totally, the results of the study showed that methanolic extract of brown algae, padina gymnospora, can be considered a potential resource of antimicrobial compounds aiming to replace chemical medicines.