Antibacterial activity of buckwheat honey added with ferrous lactate against Pseudomonas aeruginosa

Hydroxyl radical (OH∙) in honey has been identified to cause damage to bacteria that degrades DNA, stalls growth and even kills cells. This study investigated the action model of OH∙ induced by exogenous ferrous iron. Our data showed that ferrous lactate augmented the antibacterial activity of buckwheat honey by producing OH∙ that targeted at components in the respiratory system and the metabolic system such as NADH dehydrogenases and 6-phosphogluconate dehydratases in Pseudomonas aeruginosa. After buckwheat honey was pretreated with ferrous lactate, the activities of NADH dehydrogenases and 6-phosphogluconate showed 79.9% and 99.7% reduction respectively. Activities of these enzymes were much less affected if OH∙ was scavenged by α-tocopherol. OH∙ in buckwheat honey also increased malondialdehyde production from 0.54 to 6.87 nmoL/g and seriously damaged the cell membrane in P. aeruginosa. This damage ramped up the membrane permeability and increased protein leakage from 0.02 to 1.87 μg/mg. Our results indicate that in such action model exogenous ferrous lactate brings on cell decomposition and increases bactericidal activity of buckwheat honey.