Antimicrobial properties of extracts from the green seaweed Ulva fasciata Delile against pathogenic bacteria and fungi
Paulert, Roberta Júnior; Smania Stadnik, Marciel J.; Pizzolatti, Moacir G.
Cell-wall polysaccharides and crude extracts from the seaweed Ulva fasciata were studied for their antimicrobial activity against filamentous fungi, yeast and bacteria. Polysaccharides were extracted with hot water, precipited in ethanol and identified by 1H and 13C-NMR as an ulvanobiuronic acid 3-sulfate repetead structure (ulvan). To obtain crude extracts, the dried alga was extracted with methanol in soxhlet apparatus. The anti-bacterial activity was assessed by agar diffusion assay and by means of the broth dilution method estimating the minimal inhibitory concentration (MIC). The following human bacterial and yeast strains were tested: Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus cereus, Micrococcus luteus and Candida albicans and, two plant pathogens: Xanthomonas campestris and Erwinia carotovora. MIC was determined for the fungi Colletotrichum lindemuthianum (plant pathogen), Trichophyton mentagrophytes and Microsporum canis (dermatophyte pathogens). Both methanol soluble and -insoluble (remaining fraction) extracts were active against P. aeruginosa, X. campestris and E. carotovora. The highest activity of extracts was observed against Erwinia (MIC 1 mg/ml). The methanol-insoluble extract inhibited the growth of T. mentagrophytes at concentration of 2 mg/ml. In contrast, ulvans did not show any in vitro activity towards all test organisms.