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Bioactive phytocompounds are studied by several bioactivities demonstrated, as their cytotoxic effects. The aim of this work was to evaluate the phytochemical profile, the toxic effect using the Drosophila melanogaster animal model and the anti-inflammatory and antimicrobial effect of the Alternanthera brasiliana (EEAB) ethanol extract. The phytochemical profile was performed using HPLC. The cytotoxic effect was evaluated in vivo using D. melanogaster. The anti-inflammatory effect was determined by neurogenic and antiedematogenic assays, and the antimicrobial activity was assayed using a microdilution method to determine the minimum inhibitory concentration (MIC) of the EEAB alone and in association with antibiotics. The main compound identified on the EEAB was luteolin (1.93%). Its cytotoxic effect was demonstrated after 24 h in the concentrations of 10, 20 and 40 mg/mL. The extract demonstrated an antiedematogenic effect, with a reduction of the edema between 35.57 and 64.17%. The MIC of the extract was ≥1.024 μg/mL, thus being considered clinically irrelevant. However, when the EEAB was associated with gentamicin, a synergism against all bacterial strains assayed was observed: Staphylococcus aureus (SA10), Escherichia coli (EC06) and Pseudomonas aeruginosa (PA24). Due to these results, the EEAB demonstrated a low toxicity in vivo and anti-inflammatory and synergistic activities. These are promising results, mainly against microbial pathogens, and the compounds identified can be a source of carbon backbones for the discovery and creation of new drugs.

The association of herbal products with standard antimicrobial drugs has recently gained more attention as a hope to overcome infectious diseases caused by multidrug-resistant microorganisms. Here, we investigated for the first time the antimicrobial (antifungal and antibacterial) activity of ethanolic and aqueous extracts of R. echinus against multiresistant strains of bacteria (E. coli, P. aeruginosa and S. aureus) and fungi (C. albicans, C. krusei and C. tropicalis), as well as potential to enhance the activity of antibiotics drugs. In addition, both extract were chemically characterized and their toxicity was assessed in Artemia salina. Our results demonstrate that aqueous extract of R. echinus caused a significant increase in the activity of antibiotics gentamicin and imipenem, while the ethanolic extract strongly enhanced the antibiotic activity of gentamicin, amikacin, imipenem and ciprofloxacin against P. aeruginosa. However, neither the ethanolic nor the aqueous extracts significantly affect the antibiotic activity of the drugs when tested against S. aureus. Phytochemical analysis of the extracts indicated ellagic acid, caffeic acid and chlorogenic acid as the major components which can be at least in part responsible for the enhanced activity of antibiotics. None of the extracts showed toxicity in A. salina even at the highest concentration tested (1000 μg/mL). All together, our results suggest that the leaf extract of R. echinus can be an effective source of modulating agents.

The emergence of fungal resistance to commercial drugs has been a major problem for the WHO. In this context, research with natural products is promising in the discovery of new active substances. Thus, this work evaluated the antifungal effect of a medicinal plant (i.e., Mesosphaerum suaveolens) against strains of the genus Candida, tested the combined effect with the drug fluconazole, and, finally, determined the phenolic constituents present in the species. Initially, aqueous extracts of leaves (AELMs) and aerial parts (AEAPMs) of the species were prepared. For microbiological assays, the minimum fungicidal concentration was determined by broth microdilution, and the combined effect of fluconazole extracts were verified by sub-inhibitory microdilution concentrations (CFM/8) followed by spectrophotometric readings which were used to determine the IC50. HPLC detected the presence of flavonoids and phenolic acids, detecting eight compounds present in the samples of which caffeic acid and quercetin were major components. The AELMs modulated fluconazole activity since it decreased fluconazole&rsquo, s IC50 from 7.8 &micro, g/mL to an IC50 of 4.7 &micro, g/mL (CA LM 77) and from 28.8 &micro, g/mL to 18.26 &micro, g/mL (CA INCQS 40006) for the C. albicans strains. The AEAPMs were able to potentiate the effect of fluconazole more effectively than the AELMs. Such an effect was significant for the 16 &micro, g/mL concentration for CA LM 77 and 32 &micro, g/mL for CA INCQS 40006. The AEAPMs as well as the AELMs presented clinically relevant activities for C. tropicalis strains. For the C. tropicalis LM 23 strain, the AEPMs obtained an IC50 of 25 &micro, g/mL and the AELMs an IC50 of 359.9 &micro, g/mL.