The Galactose-Binding Lectin Isolated from Vatairea macrocarpa Seeds Enhances the Effect of Antibiotics Against Staphylococcus aureus-Resistant Strain.

The use of natural products together with standard antimicrobial drugs has recently received more attention as a strategy to combat infectious diseases caused by multidrug-resistant (MDR) microorganisms. This study aimed to evaluate the capacity of a galactose-binding lectin from Vatairea macrocarpa seeds (VML) to modulate antibiotic activity against standard and MDR Staphylococcus aureus and Escherichia coli bacterial strains. The minimum inhibitory concentration (MIC) obtained for VML against all strains was not clinically relevant (MIC ≥ 1024 µg/mL). However, when VML was combined with the antibacterial drugs gentamicin, norfloxacin and penicillin, a significant increase in antibiotic activity was observed against S. aureus, whereas the combination of VML and norfloxacin presented decreased and, hence, antagonistic antibiotic activity against E. coli. By its inhibition of hemagglutinating activity, gentamicin (MIC = 50 mM) revealed its interaction with the carbohydrate-binding site (CBS) of VML. Using molecular docking, it was found that gentamicin interacts with residues that constitute the CBS of VML with a score of - 120.79 MDS. It is this interaction between the antibiotic and the lectin's CBS that may be responsible for the enhanced activity of gentamicin in S. aureus. Thus, our results suggest that the VML can be an effective modulating agent against S. aureus. This is the first study to report the effect of lectins as modulators of bacterial sensitivity, and as such, the outcome of this study could lay the groundwork for future research involving the use of lectins and conventional antibiotics against such infectious diseases such as community-acquired methicillin-resistant S. aureus (MRSA).

Purification and biophysical characterization of a mannose/N-acetyl-d-glucosamine-specific lectin from Machaerium acutifolium and its effect on inhibition of orofacial pain via TRPV1 receptor.

A new mannose/N-acetyl-dglucosamine-specific lectin, named MaL, was purified from seeds of Machaerium acutifolium by precipitation with ammonium sulfate, followed by affinity and ion-exchange chromatography. MaL haemagglutinates either native rabbit erythrocytes or those treated with proteolytic enzymes. MaL is highly stable by the ability to maintain its haemagglutinating activity after exposure to temperatures up to 50 °C. The lectin haemagglutinating activity was optimum between pH 6.0 and 7.0 and inhibited after incubation with d-mannose and N-acetyl-d-glucosamine and α-methyl-d-mannopyranoside. MaL is a glycoprotein with relative molecular mass of 29 kDa (α-chain), 13 kDa (ß-chain) and 8 kDa (γ-chain) with secondary structure composed of 3% α-helix, 44% ß-sheet, 21% ß-turn, and 32% coil. The orofacial antinociceptive activity of the lectin was also evaluated. MaL (0.03 mg mL-1) reduced orofacial nociception induced by capsaicin, an effect that occurred via carbohydrate recognition domain interaction, suggesting an interaction of MaL with the transient receptor potential cation channel subfamily V member 1 (TRPV1) receptor. Our results confirm the potential pharmacological relevance of MaL as an inhibitor of acute orofacial mediated by TRPV1.

Structural analysis and anthelmintic activity of Canavalia brasiliensis lectin reveal molecular correlation between the carbohydrate recognition domain and glycans of Haemonchus contortus.

Haemonchus contortus is one of the most economically important parasites infecting small ruminants worldwide. This nematode has shown a great ability to develop resistance to anthelmintic drugs, calling for the development of alternative control approaches. Because lectins recognize and bind to specific carbohydrates and glycan structures present in parasites, they can be considered as an alternative to develop new antiparasitic drugs. Accordingly, this work aimed to investigate the anthelmintic effect of Canavalia brasiliensis (ConBr) lectin against H. contortus and to evaluate a possible interaction of ConBr with glycans of this parasite by molecular docking. ConBr showed significant inhibition of H. contortus larval development with an IC50 of 0.26 mg mL-1. Molecular docking assays revealed that glycans containing the core trimannoside [Man(α1-3)Man(α1-6)Man] of H. contortus interact in the carbohydrate recognition domain of ConBr with an interaction value of MDS = -248.77. Our findings suggest that the inhibition of H. contortus larval development is directly related to the recognition of the core trimannoside present in the glycans of these parasites. This work is the first to report on the structure-function relationships of the anthelmintic activity of plant lectins.