Investigação da atividade antibacteriana in vitro e caracterização química do extrato etanólico de folhas de Coffea arabica L.

Abstract

The Coffea arabica L. species accounts for more than 60% of all coffee worldwide produced. In fact, the product that is internationally traded is its green beans, while its leaves are considered waste. The use of coffee leaves is promising as they are widely available and are sources of several bioactive substances. Thus, the aim of this study was to evaluate the in vitro antibacterial activity of the lyophilized ethanol extract of arabica coffee leaves (EE-CaL) and to investigate the compounds present in this extract. The in vitro antibacterial effect of EE-CaL was evaluated using the broth microdilution method and the adapted drop plate agar method to determine the Minimum Inhibitory Concentration (MIC) and the Minimum Bactericidal Concentration (MBC), respectively. Reference Gram-positive bacterial strains [Staphylococcus aureus subsp. aureus Rosenbach (ATCC 29213)] and Gram-negative fermenters [Escherichia coli (Migula) Castellani and Chalmers (ATCC 25922)] and nonfermenters [Pseudomonas aeruginosa (Schroeter) Migula (ATCC 27853 and ATCC 9027)] were selected based on the list of priority pathogenic bacteria to guide the discovery, research and development of new drugs published by the World Health Organization (WHO). The chemical characterization of EE-CaL was performed using UPLC-MS-Q-ToF. EE-CaL was active against S. aureus (ATCC 29213) and E. coli (ATCC 25922), being more efficient against this strain (MIC = 2500 μg/mL and effect bactericidal), and inactive against P. aeruginosa (ATCC 27853 and ATCC 9027) at the concentrations tested. The chemical analysis of EE-CaL revealed the presence of compounds from the alkaloid class, such as trigonelline and caffeine, in addition to phenolic compounds such as quinic acid, 5-caffeioquinic acid, caffeic acid-Ohexoside, mangiferin, (epi)catechin, (epi)catechin mono glycoside and procyanidin trimer. Most of these compounds have antimicrobial activity described in the literature, including against E. coli and S. aureus, so they may be related to the antibacterial activity observed in EE-CaL in the present study.