Abstract
Cladonia verticillarislichen lectin (ClaveLL) was purified using a previously established protocol and then evaluated for its potential antimicrobial activity. Initially, the autochthonous lichen was submitted to extraction with sodium phosphate buffer pH 7.0, followed by filtration and centrifugation to obtain crude extract. A salt fractionation was performed with 30% ammonium sulfate. After centrifugation, the protein fraction was loaded onto molecular exclusion chromatography using Sephadex G-100 matrix to purify active lectin. ClaveLL showed antibacterial activity against Gram-positive (Bacillus subtilis,Staphylococcus aureus, andEnterococcus faecalis) and Gram-negative (Escherichia coliandKlebsiella pneumoniae) assayed strains, with greater inhibitory effect on growth ofE. coli(MIC of 7.18 μg mL−1). The lowest minimum bactericidal concentration (MBC, 57.4 μg mL−1) was detected againstE. faecalis. The antifungal assay performed withTrichophyton mentagrophytes,Microsporum gypseum,Trichophyton rubrum,Trichosporon cutaneum, andTrichosporon asahievaluated crude extract, fraction, and ClaveLL preparations. ClaveLL was the most active againstT. rubrumwith an inhibition percentage of 35% compared to negative control (phosphate buffer). Extract and fraction showed better activity on growth inhibition ofT. mentagrophytes(35%). The results indicate the potential of ClaveLL and otherC. verticillarispreparations as antimicrobial agents useful for applications focusing on human health.
Highlights
The treatment of diseases caused by bacteria and fungi is becoming an issue of concern, due to the growing emergence of microorganism strains resistant to drugs and opportunistic fungi that cause serious infections in humans [1, 2]
Cladonia verticillaris lichen lectin (ClaveLL) was purified through a preestablished protocol by Silva et al [10] using molecular exclusion chromatography on Sephadex G-100 matrix; the column is a viable approach since the same array can be reused efficiently at least 30 times to purify ClaveLL
A total of 8.28 mg of ClaveLL were purified from 10 g of C. verticillaris, yield similar to that obtained by Silva et al [10]
Summary
The treatment of diseases caused by bacteria and fungi is becoming an issue of concern, due to the growing emergence of microorganism strains resistant to drugs and opportunistic fungi that cause serious infections in humans [1, 2]. Microbial resistance is a genetic phenomenon, in which the microorganisms have genes that encode biochemical mechanisms which prevent drug actions. It may be caused by mutations in the reproductive process of the microorganisms or by imported genes acquired through transduction, conjugation, and transformation mechanisms [3]. Microbial resistance is sometimes due to natural evolution of microorganisms; it gains importance through the excessive use of antimicrobial substances in medical, agricultural, and veterinary practices [4]. The use of lichens in medicine is based on the fact that they contain unique and various biologically active substances, mainly with antimicrobial actions [8, 9].
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