Screening antimicrobial activity of various extracts of Gracilaria changii

The antimicrobial activities of methanol, methanol-chloroform, diethyl ether, ethyl acetate, and butanol extracts of Gracilaria changii B.M. Xia & I.A. Abbott (Gracilariaciae) were studied. These extracts were tested against 22 bacteria, six yeasts strains, and 11 fungal isolates by the disk diffusion and broth dilution methods. The results indicated that all of the solvent systems used in the study had equal effectiveness against the tested microorganisms. All of the extract preparations of G. changii showed significant activities against seven bacterial and four yeast isolates tested. The minimum inhibitory concentration (MIC) values of Pseudomonas aeruginosa and Bacillus subtilis were 6.25 and 3.125 to mg/mL, respectively, while the MIC for Candida albicans was 3.125 mg/mL. No fungal isolates showed any susceptibility against the different crude preparations of G. changii. The activities were compared to known commercialized antibiotics such as chloramphenicol and miconazole nitrate.