Atividade antimicrobiana de extratos de casca de noz pecã sob cepas de Staphylococcus aureus isoladas de mastite bovina: comparação de eficácia sob diferentes parâmetros físico- químicos

Abstract

Brazil, the world's third-largest milk producer, recorded 2.1% growth in milk production in the third quarter of 2023, reaching 24.52 billion liters annually, according to data from Conab (National Association of Agro-Industrial and Livestock Researchers). Mastitis, a common infection in dairy cattle, remains a significant challenge due to reduced productivity and increased costs. Among the main etiological agents of mastitis, Staphylococcus aureus stands out, known for its resistance to several antimicrobials. This highlights the urgent need for effective and sustainable therapeutic alternatives. This study aimed to evaluate the antimicrobial potential of hydroalcoholic and aqueous extracts of pecan shells (Carya illinoinensis) against S. aureus strains isolated from bovine mastitis, exploring the influence of variables such as solvent type (hydroalcoholic and aqueous), plant material particle size (powder and average particle size), and different extraction methods (soxhlet or infusion). To this end, samples were prepared focusing on obtaining phenolic and flavonoid compounds, whose antimicrobial activities had already been reported in the literature. The bacterial strains were subjected to Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) assays to determine the antimicrobial efficacy of the extracts. The results demonstrated that the hydroalcoholic extracts presented greater antimicrobial efficacy, with MICs of up to 6.94 µg/mL and proportionally lower MBCs, regardless of particle size. In contrast, aqueous extracts, especially those extracted using a coffee maker, presented higher MICs and lower efficacy. These findings indicate that the type of solvent used has a significant impact on antimicrobial activity, with hydroalcoholic extracts being more effective due to the greater solubilization of bioactive compounds. This study contributes preliminarily to the development of sustainable alternatives for managing bacterial infections in production animals, highlighting the use of agro-industrial by-products as sources of natural antimicrobial compounds.