Antibacterial activity of Theobroma grandiflorum Schum leaves’ extract against Escherichia coli and Staphylococcus aureus

Resumo

The present study aimed to obtain ethanol extract of Theobroma Grandiflorum Schum (cupuaçu) leaves and evaluate the antibacterial activity of the obtained extract against Escherichia coli and Staphylococcus aureus. The leaves were collected in two different periods of the year and divided into two groups (Group 1 and Group 2), in order to investigate the influence of season of leaves collecting on the effectiveness of the extract. The leaves were cleaned, dried (50 °C/12 h) and grinded for posterior addition of ethanol. Grinded leaves and ethanol mixture was heated (50 °C/1 h) and left to rest (24 h). Solid and liquid parts were separated by filtration. Soxhlet technique was used to recover the ethanol from the separated liquid part. Complete ethanol removal was achieved using an oven, to obtain the dry extract (DLE). The yield obtained was 1.46% and 1.54% for the first and second group, respectively. The extract obtained was diluted in DMSO in distinct proportions (1:3, 1:7, 1:9 (extract: DMSO (w/w)) and tested against Escherichia coli and Staphylococcus aureus, both at a concentration of 10⁹ and 10⁵ CFU mL^-1, based on the disk diffusion technique. Using the extract from the first group of leaves against 10⁹ CFU mL^-1 density population, both bacteria were classified as intermediate sensitive. Using the extract obtained from the second group of leaves against 10⁵ CFU mL^-1, it was observed that S. aureus kept classified as intermediate sensitive while E. coli was classified as resistant. The results suggest that the DLE can inhibit the growth of tested bacteria. Thus, further studies may be carried out in order to (a) investigate the DLE as a natural product for food preservation and (b) support the search of food industry for alternatives to control such microorganisms.