Avaliação da atividade antioxidante e antibacteriana de própolis oriunda de abelhas sem ferrão (meliponíneos) de Pato Branco - PR

Abstract

Propolis is a product of beekeeping and is a complex mixture of many chemical compounds, mainly phenolic compounds. Many of these compounds are recognized for their antioxidant and antimicrobial activity. Propolis from stingless bees, from the Apidae Family and Meliponine Subfamily, has been attracting the interest of researchers all over the world, opening a range of opportunities for its application, especially in countries where there is a rich biodiversity of plant species. Since the chemical composition of propolis is influenced by geographic origin, climate, collection site and collection time (seasonality). The extraction conditions and quantification methods of bioactive compounds, especially phenolic compounds, also influence the results. The objective of this study was to determine the content of total phenolic compounds (TFC) and evaluate the antioxidant and antibacterial properties of propolis from 3 species of bees from the Subfamily Meliponíneas - stingless bees. Thus, the propolis of the species Melipona quadrifasciata, Tetragonisca angustula and Plebeia droryana from the region of Pato Branco, PR, were evaluated in this study. Two ethanol extracts of propolis (EEP) for each species were prepared: one extract with 20% ethanol (v/v) and another with 80% ethanol (v/v) in an ultrasonic bath at 25 ºC for 40 minutes. The CFT content was determined by the Folin-Ciocalteu method and the result expressed in gallic acid equivalent (EAG). Antioxidant activity (AA) was determined by the DPPH radical scavenging method and the ABTS radical. Both results were expressed in mM of TE g-1 of propolis (TE: Trolox equivalent). The AA by the Antioxidant Reducing Power of Iron (FRAP) was also determined and its result expressed in mmol Fe+2 g-1 of propolis. The CFT content was between 2.25 mg g-1 and 61.02 mg g-1. Melipona quadrafasciata propolis showed the highest CFT contents in both ethanol concentrations. The AA by DPPH radical scavenging ranged from 0.62 to 26.537 mM TE g-1, with propolis from Melipona quadrifasciata obtaining the best results, both with 80% ethanol solvent and also with 20%. For the ABTS•+ and FRAP radical scavenging analysis, the results obtained varied from 162.37 to 695.11 mM TE g-1 and between 29.18 and 367.80 mmol Fe+2 g-1, respectively. The antibacterial activity was determined by the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) in 96-well plates against the bacteria Salmonella typhimurium, Escherichia coli, Listeria monocytogenes and Bacilus subtilis. The highest antibacterial activity was found in propolis extracted with 80% ethanol and was dependent on the ethanol concentration. In this condition, all propolis showed bacteriostatic activity (MIC = 5.44 μg mL-1) against Escherichia coli. The bacteria Salmonella typhimurium, Listeria moocytogenes and Bacillus subtilis were more sensitive to EEP ethanol 80% from Plebeia droryana with MIC equal to 10.9, 5.44 and 10.9 μg mL-1 respectively. However, this extract did not show bactericidal action against Salmonella typhimurium. Propolis from Melipona quadrifasciata and Tetragonisca angustula both showed bactericidal action against Escherichia coli (MBC = 10.9 μg mL-1), while propolis from Plebeia droryana the MBC was 87.3 μg mL-1 Melipona quadrifasciata EEP showed the highest number of compounds, followed by Tetragonisca angustula and Plebeia droryana. By chromatographic analysis it was possible to identify in the 3 species of propolis the flavonoids catechin, epicatechin, chrysin and galangin. Also, p-coumaric, ferulic, cinnamic, phenolic acids. The main constituent of Melipona quadrifasciata EEP was ferulic acid (372.82 μg g-1) followed by p-coumaric acid (111.56 μg g-1) and cinnamic acid (67.57 μg g-1). Cinnamic acid was present in all propolis analyzed while chrysin and galangin were present only in Tetragonisca angustula. However, the antioxidant and antibacterial activities of stingless propolis extracts can be attributed to the high levels of total phenolics and the presence of compounds such as ferulic acid, p-coumaric acid, cinnamic acid and catechin. This study suggests that propolis has potential application in the pharmaceutical industry, as well as in food and nutritional supplements as a natural antioxidant and antibacterial agent.