Antimicrobial and antioxidant activity of proteins isolated from Melipona beecheii honey

Proteins from Melipona beecheii honey were purified by concanavalin A (conA) affinity chromatography and eluted with a stepwise glucose gradient into fractions named F2-F5. The conA-unbound fraction (F1) was further separated by molecular exclusion into fractions named MbF1-1,2 and MbF1-3. All fractions were evaluated for antibacterial activity against foodborne pathogens and antioxidant capacity. F1 fraction possessed highest antimicrobial activity against S. aureus, L. monocytogenes, S. Typhimurium, E. coli and P. aeruginosa with MIC's 1.4 ± 0.2, 15 ± 1, 39 ± 2, 1 ± 0.1, and 75 ± 2 µg/mL, respectively. F1, MbF1-1,2 and MbF1-3 had bactericidal effect except against P. aeruginosa. When the antioxidant capacity of the fractions was determined, F2 had the highest antioxidant activity measured by DPPH radical scavenging activity (IC₅₀ = 2.4 ± 0.4 µg/µL) and reducing power of Fe(III) (IC₅₀ = 1.8 ± 0.2 µg/µL). We provide evidence that M. beecheii honey proteins possess broad spectrum antibacterial and antioxidant activity, the latter probably through their reducing agent and free radical scavenger properties.