Xylella fastidiosa is a plant-pathogenic bacterium that lives inside host xylem vessels, where it forms biofilm which is believed to be responsible for disrupting the passage of water and nutrients. Pectobacterium carotovorum is a Gram-negative plant-specific bacterium that causes not only soft rot in various plant hosts, but also blackleg in potato by plant cell wall degradation. Chagas disease, which is caused by Trypanosoma cruzi, has been commonly treated with nifurtimox and benzonidazole, two drugs that cause several side effects. As a result, the use of natural products for treating bacterial and neglected diseases has increased in recent years and plants have become a promising alternative to developing new medicines. Therefore, this study aimed to determine, for the first time, the chemical composition of essential oil from Psidium guajava flowers (PG-EO) and to evaluate its in vitro anti-Xylella fastidiosa, anti-Pectobacterium carotovorum, anti-Trypanosoma cruzi and cytotoxic activities. PG-EO was obtained by hydrodistillation in a Clevenger apparatus while its chemical composition was determined by gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). Major compounds identified in PG-EO were α-cadinol (37.8%), β-caryophyllene (12.2%), nerolidol (9.1%), α-selinene (8.8%), β-selinene (7.4%) and caryophyllene oxide (7.2%). Results showed that the PG-EO had strong trypanocidal activity against the trypomastigote forms of Trypanosoma cruzi (IC50 = 14.6 μg/mL), promising antibacterial activity against X. fastidiosa (MIC = 12.5 μg/mL) and P. carotovorum (MIC = 62.5 μg/mL), and moderate cytotoxicity against LLCMK2 adherent epithelial cells in the concentration range (CC50 = 250.5 μg/mL). In short, the PG-EO can be considered a new source of bioactive compounds for the development of pesticides and trypanocide drugs.

Helicobacter pylori is a Gram-negative, microaerophilic, curved-rod, flagellated bacterium commonly found in the stomach mucosa and associated with different gastrointestinal diseases. With high levels of prevalence worldwide, it has developed resistance to the antibiotics used in its therapy. Brazilian red propolis has been studied due to its biological properties, and in the literature, it has shown promising antibacterial activities. The aim of this study was to evaluate anti-H. pylori from the crude hydroalcoholic extract of Brazilian red propolis (CHEBRP). For this, in vitro determination of the minimum inhibitory and bactericidal concentration (MIC/MBC) and synergistic activity and in vivo, microbiological, and histopathological analyses using Wistar rats were carried out using CHEBRP against H. pylori strains (ATCC 46523 and clinical isolate). CHEBRP presented MIC/MBC of 50 and 100 μg/mL against H. pylori strains (ATCC 43526 and clinical isolate, respectively) and tetracycline MIC/MBC of 0.74 µg/mL. The association of CHEBRP with tetracycline had an indifferent effect. In the stomach mucosa of rats, all treatments performed significantly decreased the number of H. pylori, and a concentration of 300 mg/kg was able to modulate the inflammatory response in the tissue. Therefore, CHEBRP showed promising anti-H. pylori in in vitro and in vivo assays.

Considering our previous findings on the remarkable activity exhibited by cobalt(III) with 2-acetylpyridine-N(4)-R-thiosemicarbazone (Hatc-R) compounds against Mycobacterium tuberculosis, the present study aimed to explored new structure features of the complexes of the type [Co(atc--R)₂]Cl, where R = methyl (Me, 1) or phenyl (Ph, 2) (¹³C NMR, high-resolution mass spectrometry, LC–MS/MS, fragmentation study) together with its antibacterial and antiviral biological activities. The minimal inhibitory and minimal bactericidal concentrations (MIC and MBC) were determined, as well as the antiviral potential of the complexes on chikungunya virus (CHIKV) infection in vitro and cell viability. [Co(atc-Ph)₂]Cl revealed promising MIC and MBC values which ranged from 0.39 to 0.78 µg/mL in two strains tested and presented high potential against CHIKV by reducing viral replication by up to 80%. The results showed that the biological activity is strongly influenced by the peripheral substituent groups at the N(4) position of the atc-R¹⁻ ligands. In addition, molecular docking analysis was performed. The relative binding energy of the docked compound with five bacteria strains was found in the range of −3.45 and −9.55 kcal/mol. Thus, this work highlights the good potential of cobalt(III) complexes and provide support for future studies on this molecule aiming at its antibacterial and antiviral therapeutic application.

The microorganisms that constitute the oral microbiome can cause oral diseases, including dental caries and endodontic infections. The use of natural products could help to overcome bacterial resistance to the antimicrobials that are currently employed in clinical therapy. This study assessed the antimicrobial activity of the Copaifera pubiflora oleoresin and of the compounds isolated from this resin against oral bacteria. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays provided values ranging from 6.25 to > 400 μg/mL for the C. pubiflora oleoresin and its isolated compounds. The fractional inhibitory concentration index (FICI) assay showed that the oleoresin and chlorhexidine did not act synergistically. All the tested bacterial strains formed biofilms. MICB50 determination revealed inhibitory action: values varied from 3.12-25 μg/mL for the oleoresin, and from 0.78 to 25 μg/mL for the ent-hardwickiic acid. Concerning biofilm eradication, the C. pubiflora oleoresin and hardwickiic acid eradicated 99.9 % of some bacterial biofilms. Acid resistance determination showed that S. mutans was resistant to acid in the presence of the oleoresin and ent-hardwickiic acid at pH 4.0, 4.5, and 5.0 at all the tested concentrations. Analysis of DNA/RNA and protein release by the cell membrane demonstrated that the oleoresin and hardwiickic acid damaged the bacterial membrane irreversibly, which affected membrane integrity. Therefore, the C. pubiflora oleoresin and ent-hardwickiic acid have potential antibacterial effect and can be used as new therapeutic alternatives to treat oral diseases such as dental caries and endodontic infections.