Potencial bioativo de extratos da microalga Arthrospira platensis

Abstract

Research on new sources of natural products found in microalgae alternative sources of metabolites with remarkable biological and biochemical properties due to the diversity of their molecules and complex chemical structures. The present work had as objective to study the biological potential of the extracts of the cyanobacteria Arthrospira platensis, commonly known as Spirulina. For this, four extracts were prepared with increasing polarity solvents (hexane – Hx, ethyl acetate – AcOEt, methanol – MeOH, and methanol:water 1:1 – MeOH:H2O 1:1) and evaluated specifically for the content of total phenolic compounds (TPC), the flavonoid (flavonols and flavones of luteolin subgroup) quantification (FC), and the in vitro antioxidant activities, measured by the DPPH radical scavenging activity, ferrous ion-chelating ability (FIC), ferric reducing antioxidant power (FRAP) and β-carotene bleaching (BCB) inhibitory activity. The minimum inhibitory concentration (MIC), performed by standard microdilution technique, was tested against the bacteria Escherichia coli, Staphylococcus aureus and Salmonella ser. Braenderup. The antifungal activity, performed by the disc diffusion technique, was tested against the filamentous fungus Aspergillus niger and the yeast Candida albicans. The antibiofilm activity, determined by the adhesion technique in polystyrene microplates, was performed against the strain Pseudomonas aeruginosa. The anticancer activity was investigated by the effect of extracts of A. platensis on the cell viability of MCF-7 (breast adenocarcinoma) and LNCaP clone FGC (metastatic prostate carcinoma). The CFT values (mg EAG g-1 extracts Hx, AcOEt, MeOH and MeOH: H2O 1:1) were 73.34, 99.00, 30.49 and 26.21, respectively. The FC values (mg EQ g-1 extract Hx, AcOEt and MeOH) were 318.15, 474.65 and 73.05, respectively. In vitro antioxidant activities measured by DPPH, FIC and BCB were higher in the AcOEt extract, whereas FRAP was higher in the MeOH:H2O (1:1) extract. No extract showed antimicrobial activity in MIC against E. coli, S. aureus and Salmonella ser. Braenderup, but a bacteriostatic activity of the Hx extract was observed against the S. aureus strain at the concentration of 1000 μg mL-1. No inhibition of P. aeruginosa biofilm formation was observed for any of the extracts tested. It was not possible to observe antifungal activity against C. albicans, but it was observed a fungistatic activity against A. niger caused by the AcEOt extract at the concentration of 500 μg mL-1. The cell viability of the LNCaP line was 71.11%, 35.08% and 61.48% for the extracts Hx, AcOEt and MeOH, respectively, whereas for MCF-7 cells, it was 67.29%, 86.56% and 60.98% for extracts Hx, AcOEt and MeOH, respectively. The crude extracts of the A. platensis microalga presented high levels of phenolic and flavonoids compounds, being considered a natural source of these antioxidants. The crude extracts did not 9 show strong antimicrobial activity. The extracts of A. platensis are a promising source for the production of drugs for the control of the growth of MCF7 and LNCaP cancer cell lines. Further studies are needed to identify the bioactive compounds present in extracts of A. platensis, especially in the AcOEt extract.