Browsing by Author "Ribon, Andrea de Oliveira Barros"

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    Antibacterial screening of plants from the Brazilian Atlantic Forest led to the identification of active compounds in Miconia latecrenata (DC.) Naudin.
    (2020) Rodrigues, Laís Azevedo; Almeida, Ayla das Chagas; Gontijo, Douglas da Costa; Salustiano, Iorrana Vieira; Almeida, Alisson Andrade; Brandão, Geraldo Célio; Ribon, Andrea de Oliveira Barros; Leite, João Paulo Viana
    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 frac tionation of EMl and metabolite profiling performed by UPLC DAD-MS/MS, the ethyl acetate (AFMl) and aqueous (WFMl) frac tions showed a mixture of phenolic compounds derived from ellagic acid and quercetin. The MIC value of AFMl was two-times 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.
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    Prenylated flavonoid-enriched fraction from maclura tinctoria shows biological activity against Staphylococcus aureus and protects galleria mellonella larvae from bacterial infection.
    (2019) Almeida, Ayla das Chagas; Rodrigues, Laís Azevedo; Paulino, Graziela dos Santos; Aguilar, Ananda Pereira; Almeida, Alisson Andrade; Ferreira, Sukarno Olavo; Brandão, Geraldo Célio; Leite, João Paulo Viana; Ribon, Andrea de Oliveira Barros
    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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    Quorum sensing regulated phenotypes in Aeromonas hydrophila ATCC 7966 deficient in AHL production.
    (2016) Rossi, Adriana dos Reis Ponce; Pinto, Uelinton Manoel; Ribon, Andrea de Oliveira Barros; Bazzolli, Denise Mara Soares; Vanetti, Maria Cristina Dantas
    The virulence of Aeromonas hydrophila is positively regulated by a quorum sensing (QS) system based on the ahyRI genes. The aim of this study was to evaluate the phenotypic characteristics related to virulence in the A. hydrophila strain ATCC 7966 in order to check if virulence traits are still functioning, despite the absence of a well characterized QS system. As expected, we were not able to detect quorum signaling AHL molecules in A. hydrophila ATCC 7966 by cross-streaking or thin layer chromatography with AHL biosensor strains. Although A. hydrophila ATCC 7966 did not produce AHLs, transcription of the ahyI and ahyR genes was observed by RT-PCR. Phenotypes generally recognized as QS-regulated in A. hydrophila were maintained in ATCC 7966; these phenotypes included proteolytic activity on casein and gelatin and amylolytic, lipolytic, and β- hemolytic activities, as well as the ability to adhere to surfaces and to form biofilms. Moreover, the addition of exogenous AHLs did not induce changes in the evaluated phenotypes. The results suggest that although this strain does not produce AHL as evaluated in this study, it maintains the phenotypes commonly associated with QS in this species indicating that other regulatory mechanisms independent of ahyRI may be in place.