Atomic force microscopy evidences of bacterial cell damage caused by propolis extracts on E. coli and S. aureus

Abstract

The interaction of the aqueous extract of green propolis with the bacterial envelope was investigated using atomic force microscopy on E. coli and S. aureus, as Gram-negative and Gram-positive model microorganisms. The bacteria were incubated in the extracts with variable proportions of water/ethanol, i.e., in different concentrations of total phenolic and flavonoids, for 4 and 12 hours. All extracts exhibited antibacterial action with higher activity (lower MOC) for full ethanolic extract (100% alcohol) against both strains, what was attributed to a synergistic interaction of ethanol and phenolic compounds presented in greater concentration in this extract. According to AFM analysis, it was evidenced the propolis main mechanism of action as rupture and lysis of bacterial cells. Changes in bacterial morphology following treatment indicate membrane imbalances with the internal contents leaking out accompanied by cell swelling, due to possible water uptake through cell lysis. The intensity of such damage was found to be time and specie dependent.

Propolis and its potential against SARS-CoV-2 infection mechanisms and COVID-19 disease

“…Propolis components galangin, pinocembrin, rutin, quercetin, and naringenin, as well as CAPE increase bacterial membrane permeability, which could explain their antimicrobial properties [ 188 ]. De Campos et al [ 189 ] showed that the main mechanism of action of propolis is rupture and lysis of bacterial cells. Propolis has demonstrated antibacterial activity against Staphylococcus aureus , Staphylococcus epidermidis , and E. coli [ 190 ], including methicillin-resistant and methicillin-susceptible strains of Staphylococcus aureus [ 191 ].…”

“…Considerable work has gone into understanding the mechanisms involved in the biological properties of propolis [ 54 , 189 , 204 , 205 ]. Also, efforts have been made to improve technological and analytical processes to determine adequate extraction procedures that preserve its bioactive compounds and consistently provide the best pharmacological properties for each medical condition [ 50 , 200 , 201 , 203 , [206] , [207] , [208] ].…”

Propolis particles incorporated in aqueous formulations with enhanced antibacterial performance

“…However, there is evidence of sonication-assisted dissolution of functional compounds to the carrier phase. Campos, Assis and Bernardes-Filho (2020) , compared the amount of phenolic compounds extracted in different fractions of water and ethanol, reporting that the percentage concentration reached a maximum when 1:1 ratio of ethanol and water was used, clarifying that some phenolic compounds can be partially water soluble.…”

Processamento e análise de extratos de própolis verde como potencial sanitizante de uso hortifrutícola

“…Os testes de coleta e inoculação dos resíduos bacterianos obtidos da superfície vítrea, após 2h da pulverização do extrato, não resultou em crescimento de nenhuma das bactérias previamente imobilizadas, indicando uma ação eficiente na redução do crescimento microbial. Estudos complementares, previamente realizados nestas mesmas condições indicaram por observações microscópicas que os microrganismos sofrem alterações morfológicas, resultando em estruturas disformes e rupturas decorrentes de bacteriólise (Campos et al, 2020). Adicionalmente medidas volumétricas comparativas confirmaram a ocorrência de vazamentos de fluidos intracelulares em razão de rupturas no envelope celular (Campos 2017;Campos et al, 2020).…”

“…Estudos complementares, previamente realizados nestas mesmas condições indicaram por observações microscópicas que os microrganismos sofrem alterações morfológicas, resultando em estruturas disformes e rupturas decorrentes de bacteriólise (Campos et al, 2020). Adicionalmente medidas volumétricas comparativas confirmaram a ocorrência de vazamentos de fluidos intracelulares em razão de rupturas no envelope celular (Campos 2017;Campos et al, 2020). por De Castro (2001), os flavonoides e derivados são os principais agentes associados às atividades antibacterianas de extratos de própolis de diferentes origens.…”