Atividades antioxidante, antimicrobiana, antibiofilme e citotóxica de extratos da macroalga marinha parda Lobophora variegata (J. V. Lamouroux)

Abstract

The diversity of marine macroalgae is directly associated to environmental conditions so that, in adverse circumstances, they can synthesize metabolites for selfprotection. Flavonoids constitute one of the main groups of phenolic compounds. Found in large quantities in plants, they perform defense functions and are potential sources to prevent damages associated with cellular oxidation and to avoid attacks of microorganism. The objective of this work was to investigate the biological activities of dichloromethane (DCM) and 70% ethanol (EtOH 70%) extracts of the brown marine alga Lobophora variegata, collected at Paracuru beach-Ceará. Additionally, the extracts were examined for total phenolic content (TPC), total flavonoid content (TFC) and in-vitro antioxidant activity, measured through DPPH radical scavenging activity (DPPH), ferrous ion chelating activity (FIC), ferric ion reduction power (FRAP), -carotene bleaching (BCB), and also for antibacterial, antifungal, antibiofilm and cytotoxic activities. Oven-dried alga was used for preparation of DCM and EtOH 70% extracts, which were re-suspended in 50% methanol (MeOH 50%) to achieve a concentration of 1000 µg mL-1, which after successive dilutions resulted in concentrations ranging from 500 to 7.8125 µg mL-1. Both antioxidant and cytotoxic activities were determined for the DCM and EtOH 70% extracts at concentrations ranging from 7.8125 to 1000 µg mL-1. Subfractions obtained from column chromatography were analyzed for antimicrobial and antibiofilm activities. The yield of DCM and EtOH 70% extracts were 3.1% and 4.8%, respectively. EtOH 70% extracted the highest quantities of TPC and TFC and showed the highest antioxidant activity. Two subfractions of DCM extract were effective against Escherichia coli (ATCC25922) at 100 and 1000 g mL-1, while three others were effective against Staphylococcus aureus (ATCC25923) at the highest concentration. No subfraction showed antifungal activity against Aspergillus niger nor Saccharomyces cerevisiae. Neither did they contribute to the inhibition of the formation of Pseudomonas spp. biofilm. DCM extract at concentrations of 125, 250 and 500 g mL-1 showed a dose-dependent cytotoxic activity with Artemia sp. nauplii, killing 100% of individuals after 48 h exposure. Cytotoxic activity results for the EtOH 70% extract were not shown because the percentage of dead nauplii in the control was higher than the acceptable maximum of 10%. Lobophora variegata presents different biological activities, and further investigation of its potential should be carried out on subfractions in order to verify their therapeutic efficacy