Otimização da extração de compostos fenólicos de brácteas estéreis de Araucaria angustifolia baseado nas propriedades químicas e bioatividade

Abstract

The sterile bracts, which represent approximately 80% of Araucaria angustifolia pinecone, are a source of phenolic compounds that have antioxidant and antimicrobial activity. These compounds can be recovered and applied in food products, aiming to increase the content of bioactive compounds, antioxidant and antimicrobial activities, as well as functional properties. Therefore, the extraction of these was optimized using the response surface methodology through Box Behnken planning. The phenolic characterization was performed by quantifying the content of total phenolic compounds, total flavonoids, flavonols and condensed tannins, while the quantification and identification of individual phenolic compounds were performed by High Performance Liquid Chromatography. The antioxidant activity was evaluated by methods based on the capture of 2,2-diphenyl-1-picryl-hydrazyl (DPPH) and 2,2'-azinobis(3- ethylbenzenethiazoline)-6-sulfonic (ABTS) radicals, and by ferric reducing antioxidant power (FRAP) and copper reducing antioxidant capacity (CUPRAC). The antimicrobial activity was evaluated as the minimum inhibitory concentration by the broth microdilution technique, while the antiglycemic activity was performed through the inhibition of α-glucosidase. The analysis of cell-based activities was performed through cytotoxicity, cellular antioxidant, antiinflammatory and anti-proliferative analyses. The optimization indicated optimal extraction conditions when obtained with 60% ethanol (v/v), solute/solvent ratio of 1:38 (w/v) and at a temperature of 80 ºC. The compounds observed in the extract were gallic acid, catechin, epicatechin, quercetin and kaempferol, which are related to bioactive properties. The extract showed high levels for the phenolic classes and antioxidant activity by the analyzed methods. The inhibitory activity at the concentration of 10,000 µg/mL was 81.3%, 86.9%, 83.5% and 79.7% for Staphylococcus aureus, Enterococcus spp., Salmonella spp. and Escherichia coli, respectively, while for Lactobacillus brevis the extract inhibited 27.9% and 19.5% at concentrations of 15,000 and 10,000 µg/mL, respectively. However, at lower concentrations, L. brevis showed resistance, indicating that the extract could be applied to fermented dairy products, aiming to obtain a functional product, due to its antiglycemic property, which demonstrated α-glucosidase inhibitory activity approximately 10 times higher than the drug used for this purpose. The extract did not show cellular antioxidant and anti-inflammatory activity, but showed antiproliferative activity against tumor cells (stomach, intestine and breast carcinoma). However, the extract showed toxicity to non-tumor cells PLP2 (GI50 = 41 ± 3 µg/mL) and VERO (GI50 = 75 ± 7 µg/mL). Therefore, future studies can be carried out to elucidate more information about the toxic activity of the extract to be applied in foods, including with other extraction methods and solvents.