Banca de DEFESA: STELLA FREITAS DE QUEIROZ

PURIFICATION, CHARACTERIZATION AND EVALUATION OF THE ANTIMICROBIAL ACTIVITY OF THERMOSTABLE LECTIN FROM SHELLS OF Abarema cochliacarpos (GOMES 1803) BARNEBY & GRIMES 1996

Medicinal plant, barbatimão, lectin, antimicrobial activity.

Several plants are used by man for therapeutic use and propagated over generations. Currently there is a growth in research seeking to identify and isolate active substances present in these organisms in order to identify new drugs. The production of the active principles of these organisms is related to their defense mechanism against external agents. These substances are normally classified into primary and secondary metabolites. Lectins are proteins of primary metabolism that can assume several biological roles, including antibacterial, antifungal, anti-inflammatory, antitumor and healing activities. These activities are related to the ability of lectins to bind to carbohydrates present on the cell surface of target organisms, preventing their development and/or inducing a cellular response. Abarema cochliacarpos (Gomes) Barneby & Grimes, popularly known as barbatimão, is a plant used in folk medicine to treat ulcers, wounds, skin infections, gastritis, among others. This study aims to purify, characterize and evaluate the antimicrobial activity of the bark lectin of A. cochliacarpos. The extract was prepared, filtered over activated charcoal and an aliquot of this filtrate was applied to a chitin chromatographic column. Proteins of interest were eluted with 1M acetic acid. Then, the sample was dialyzed to remove the elution solution and its hemagglutinating activity (512) was evaluated. It was possible to confirm the purification of the lectin, called AcBL (lectin from the bark of A. cochliacarpos), through SDS-PAGE electrophoresis under non-reducing conditions; the gel showed the presence of a protein band representing a molecular mass of 51 kDa. Protein dosage was performed at all stages of purification, as well as characterization tests. AcBL was inhibited by casein, showed thermostability in a wide temperature range, proved to be an acid-neutral protein and had its activity reduced in the presence of EDTA, calcium and magnesium ions. AcBL showed antibacterial activity against A. baumannii, E. faecalis, E. coli, K. pneumoniae, S. enteritidis and S. pyogenes, exhibited antifungal activity against C. neoformans and C. gattii and was able to inhibit the biofilm formed by C. neoformans. In this way, the barbatimão bark lectin can be applied as an alternative in the treatment of diseases caused by pathogenic microorganisms. The development of this work contributes to the isolation of new antimicrobial proteins, with regional relevance when investigating lectins from a medicinal plant in Northeast Brazil, which may represent a new biomaterial with high biotechnological potential.