Casca de noz pecan - atividade antioxidante, antibacteriana e baixa toxicidade: aplicação no controle da mastite bovina

Abstract

Bovine mastitis is one of the main problems that affect dairy cattle, and it is difficult to treat, which is usually performed through the use of antibiotics, which can pose risks to public health. This disease is an inflammatory process caused by the action of microorganisms such as Staphylococcus aureus, a bacterium often associated with resistant cases of mastitis. Thus, new therapeutic approaches are necessary, and in this sense, phytotherapy has stood out, being the subject of different studies. Among the various species that have been studied, there is the pecan nut, whose shell has aroused the interest of the scientific community, considering that some studies have already identified its potential antioxidant and antimicrobial action, useful in the treatment of some diseases. Thus, the present study aimed to evaluate the antimicrobial activity of the hydroalcoholic extract (HE) of pecan nut shell (Carya illinoinensis) against 25 strains of S. aureus isolated from bovine mastitis, as well as its antioxidant activity and toxicity. , in vitro. HE was produced from Soxhlet extractor at a concentration of 20%, 50 grams of bark for 250 mL of solvent (125 mL of water and 125 mL of ethanol). Subsequently, the HE was characterized, from the identification of bioactive compounds by means of analysis in high performance liquid chromatogram (HPLC), determination of phenolic compounds and flavonoids. In addition, the antioxidant activity of HE was evaluated by the DPPH method. The antibacterial analysis was performed by determining the minimum inhibitory concentration (MIC), by the broth microdilution technique, as well as by determining the minimum bactericidal concentration (MBC), in plates with MullerHinton agar medium. The ability of HE to reduce biofilm formation was also evaluated, through the method that uses crystal violet dye and its ability to penetrate the bacterial wall. Subsequently, the toxicity of HE was evaluated through the hemolysis test. Finally, the data obtained were statistically evaluated using the GraphPad Prism statistical program. Through the qualitative analysis of HE, the presence of phenols and flavonoids was identified in a concentration of 0.051 and 0.388 mg GAE.g–1, respectively. Regarding the concentration of bioactive compounds, the HPLC analysis identified the presence of gallic acid at an average concentration of 26.08 µg/mL. It was found that HE presented a percentage of 93% of antioxidant activity by the DPPH radical capture method. Regarding the antibacterial activity, in 91.66% of the S. aureus strains, the concentration of 32.5 mg/mL of HE showed an inhibitory and bactericidal effect, including a potential antibiofilm effect in 76% of the tested strains. The average percentage of hemolysis obtained in the toxicity test was 7.74%, within the proposed limits. Therefore, the in vitro tests of this experiment suggest that the HE from pecan nut may represent a viable alternative for the treatment of resistant cases of bovine mastitis, and may be a promising alternative for the development of therapeutic formulations for in vivo tests.