SummaryPlant biodiversity is a source of potential natural products for the treatment of many diseases. One of the ways of discovering new drugs is through the cytotoxic screening of extract libraries. The present study evaluated 196 extracts prepared by maceration of Brazilian Atlantic Forest trees with organic solvents and distilled water for cytotoxic and antimetastatic activity. The MTT assay was used to screen the extract activity in MCF‐7, HepG2 and B16F10 cancer cells. The highest cytotoxic extract had antimetastatic activity, as determined in in vitro assays and melanoma murine model. The organic extract of the leaves of Athenaea velutina (EAv) significantly inhibited migration, adhesion, invasion and cell colony formation in B16F10 cells. The phenolic compounds and flavonoids in EAv were identified for the first time, using flow injection with electrospray negative ionization‐ion trap tandem mass spectrometry analysis (FIA‐ESI‐IT‐MSn). EAv markedly suppressed the development of pulmonary melanomas following the intravenous injection of melanoma cells to C57BL/6 mice. Stereological analysis of the spleen cross‐sections showed enlargement of the red pulp area after EAv treatment, which indicated the activation of the haematopoietic system. The treatment of melanoma‐bearing mice with EAv did not result in liver damage. In conclusion, these findings suggest that A velutina is a source of natural products with potent antimetastatic activity.
Antibiotic resistance is a serious global threat to public health. This has promoted the research for new drug targets, and the use of other approaches, such as antimicrobial combined therapy. The present study evaluated the antibacterial activity of 88 extracts from Brazilian Atlantic Forest trees. The organic extract from leaves of Miconia latecrenata (EMl) was the most promising for inhibiting the growth of Staphylococcus aureus (0.3 mg/mL) and Pseudomonas aeruginosa (2.5 mg/mL). After the bioguided fractionation of EMl and metabolite profiling performed by UPLC-DAD-MS/MS, the ethyl acetate (AFMl) and aqueous (WFMl) fractions showed a mixture of phenolic compounds derived from ellagic acid and quercetin. The MIC value of AFMl was twotimes lower than EMl for P. aeruginosa, suggesting that these phenolic compounds can perform bioactivity. Furthermore, EMI and AFMl showed synergism with ampicillin and tetracycline for S. aureus and P. aeruginosa, respectively. These findings suggest that extract and fractions of the Miconia latecrenata leaves can be used as therapeutic antibacterial agents.
Background
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. 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.
Methods
Extracts 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.
Results
Among 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.
Conclusion
A 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.
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