Produção de extrato da alga antártica prasiola crispa e avaliação de seus efeitos antimicrobianos

Abstract

The Antarctic algae Prasiola crispa it’s able to tolerate various conditions considered extreme, like saline stress, dehydration, coldness, windiness, successive thaw- freezing cycles and exposure to ultraviolet radiation. It is known that algae are able to produce bioactive compounds with various biological activities, including compounds with antimicrobial activitie. Therefore, this work aims to produce extracts from P. crispa and analyze its effects against two Gram-positive bacteria (Corynebacterium glutamicum and Staphylococcus aureus) and two Gram-negative bacteria (Escherichia coli and Xanthomonas campestris). Two extracts were produced, one polar and one apolar (hydroalcoolic and hexanic, respectively) in the following way: 100 g of P. crispa, already clean and dry, were macerated and, then, the solvent was added. The extracts were under agitation for 48 hours, and then, they were filtered, the solvents were evaporated and freeze-dried. The remaining extracts were solubilized with dimethylsulfoxide (DMSO) and were accomplished antimicrobial assays applying in liquid broth Luria-Bertani, the extracts of P. crispa in different concentrations and the bacteria in microplates. The microplates were incubated for 24 hours and 37 ºC and, then, the results were analyzed. After the processes of extraction and filtration, about 800 mL were recovered of each extract that, after evaporation and freeze-dried, rendered 882 mg of hydroalcoolic extract and 21 mg of the hexanic extract. Regarding the antimicrobial activity, the hexanic extract showed higher antimicrobial activity, and the minimum inhibitory concentration for C. glutamicum, S. aureus e X. campestris were 0,05 mg/mL. For the hydroalcoolic extract, it was not possible to determine a minimum inhibitory concentration, due to the fact that was only a partial inhibition of bacterial growth. E. coli were the only bacteria that was not susceptible to the effects of both extracts. P. crispa demonstrated antimicrobial potential against the species tested, thus becoming one more possibility in the fight against microorganisms and their mechanisms of resistance to the known antibiotics.