Abstract
BackgroundThe Atlantic Forest biome extends along the entire Brazilian coast and is home to approximately 20,000 plant species, many of which are endemic; it is considered one of the hotspot regions of the planet. Several of these species are sources of natural products with biological activities that are still unknown. In this study, we evaluated the antimicrobial activity of 90 extracts derived from native Atlantic Forest tree species against Staphylococcus aureus, an important human and veterinary pathogen.MethodsExtracts from native Atlantic Forest tree species were evaluated for their antimicrobial activity against S. aureus by in vitro standard methods. Phytochemical fractionation of the extract from Maclura tinctoria was performed by liquid-liquid partitioning. LC-DAD-ESI-MS was used for identification of constituents in the most active fraction. Damage of cells and alterations in the permeability of cell membrane were determined by atomic force microscopy (AFM) and crystal violet uptake assay, respectively. In vivo antimicrobial activity was evaluated using Galleria mellonella larvae infected with S. aureus with survival data collected using the Kaplan-Meier method.ResultsAmong the organic or aqueous extracts tested here, 26 showed biological activity. Eight species showed relevant results, with a minimum inhibitory concentration (MIC) below 1 mg/mL. Antibacterial activity was registered for three species for the first time. An organic extract from Maclura tinctoria leaves showed the lowest MIC (0.08 mg/mL). Fractionation of this extract by liquid-liquid partitioning led to obtaining fraction 11FO d with a MIC of 0.04 mg/mL. This fraction showed strong activity against veterinary S. aureus isolates and contributed to the increased survival of Galleria mellonella larvae infected with S. aureus ATCC 29213. The bacterial surface was not altered by the presence of 11FO d, and no cell membrane damage was detected. The LC-DAD-ESI/MS analyses identified prenylated flavonoids as the major constituents responsible for the antibacterial activity of this active extract.ConclusionA fraction enriched in prenylated isoflavones and flavanones from M. tinctoria showed in vitro and in vivo efficacy as antistaphylococcal agents. These findings justify the need for further research to elucidate the mechanisms of action of these compounds.
Highlights
The Atlantic Forest biome extends along the entire Brazilian coast and is home to approximately 20, 000 plant species, many of which are endemic; it is considered one of the hotspot regions of the planet
Screening of extracts for antimicrobial activity Twenty-six organic and aqueous extracts tested on S. aureus ATCC 29213 by the well diffusion test exhibited antimicrobial activity (Table 1)
The 11FO organic extract prepared from Maclura tinctoria leaves had the smallest minimum inhibitory concentration (MIC), and it was chosen for later assays
Summary
The Atlantic Forest biome extends along the entire Brazilian coast and is home to approximately 20, 000 plant species, many of which are endemic; it is considered one of the hotspot regions of the planet. Staphylococcus aureus is responsible for high rates of morbidity and mortality worldwide and is the most common cause of skin infections, it may be associated with osteomyelitis, bacteremia and sepsis [1] In cattle, it is the primary cause of mastitis, which is currently considered the main disease of dairy herds [2]. The USA 300 strain, which is associated with infections in hospitals and in the community, was initially reported in the US It has been isolated from different continents, and it has become a global concern due to its hypervirulence, reduced susceptibility to different antimicrobials and great epidemic potential
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