Gallesia integrifolia (Spreng.) Harms: In vitro and in vivo antibacterial activities and mode of action.

ETHNOPHARMACOLOGICAL RELEVANCE: Gallesia integrifolia (Phytolaccaceae) is commonly known as "pau-d'alho" in Brazil or "garlic plant" due to the strong scent of garlic peculiar to all parts of the plant. The bark decoction is used for the treatment of microbial infections among other diseases by different ethnic groups in Brazil, Peruvian Amazonians, Bolivia and Mosetene Indians. This study aimed to advance in the antibacterial activity and characterize the mode of action of the hydroethanolic extract of the inner stem bark of G. integrifolia (HEGi) using in vivo and in vitro experimental models. MATERIALS AND METHODS: The qualitative and quantitative phytochemical analyzes of HEGi were carried out using colorimetric and HPLC technique. The cytotoxic potential of HEGi was evaluated against CHO-K1 cells by Alamar blue assay and its acute toxicity was assessed by the Hippocratic screening test using Swiss-Webster mice. The antibacterial activity was evaluated by micro- dilution method against ten strains of Gram-positive and Gram-negative bacteria. The mode of action of HEGi was investigated by outer membrane permeability, nucleotide leakage and potassium efflux assays. In vivo infection model was established by using Staphylococcus aureus infection model Wistar rats. RESULTS: Qualitative phytochemical analysis of HEGi revealed the presence of saponins, alkaloids, phenolic compounds and flavonoids. Phytochemical quantification of HEGi showed that higher total phenolic (80.10±0.62mg GAE/g) and flavonoid (16.10±0.03mg RE/g) contents. HPLC fingerprint analysis revealed the presence of gallic acid, rutin, and morin. In the Alamar blue assay no cytotoxic effect of HEGi in CHO-K1 cells was observed up to 200µg/mL, and no signs or symptoms of acute toxicity were observed in mice of both sexes at higher doses of up to 2000mg/kg, p.o. HEGi demonstrated bacteriostatic effect against selected Gram positive and Gram negative bacterial pathogens. Its mode of action is associated, at least partly, with changes in the permeability of bacterial membranes, evidenced by the increased entry of hydrophobic antibiotic in Pseudomonas aeruginosa, intense K(+) efflux and nucleotides leakage in Shigella flexneri, Streptococcus pyogenes and S. aureus. HEGi attenuated the experimental blood borne S. aureus infection in rats at all the tested doses levels (10, 50 and 250mg/kg). CONCLUSION: HEGi is safe at the dose tested when used acutely, and it presented broad antibacterial effect, which support its traditional use in the treatment of bacterial infections. It contains well known important phytochemicals, recognized to be active against bacterial pathogens in vitro and might be collectively responsible for the antibacterial activity of HEGi. It is bacteriostatic in nature, with membrane perturbation being one of it mode of action. HEGi represent a potential phytotherapic antibacterial agent.

Evaluation of the safety, gastroprotective activity and mechanism of action of standardised leaves infusion extract of Copaifera malmei Harms.

ETHNOPHARMACOLOGICAL RELEVANCE: Copaifera malmei Harms (Fabaceae) is a plant that occurs in the central region of Brazil, where the plant's leaves infusion is popularly used to treat gastric ulcer and inflammatory diseases. This study was aimed to investigate the gastroprotective activity and mode of action of the plants' leaves infusion in order to establish the scientific basis for such usage, and to assess its potential as a source of an anti-ulcer agent. MATERIALS AND METHODS: Leaves infusion extract of the plant (SIECm) was prepared, freeze dried and lyophilised. Its qualitative and quantitative phytochemical constituents were investigated using TLC and HPLC techniques. The safety profile was evaluated on CHO-k1 epithelial cells viability using the Alamar blue assay, and by acute toxicity test in mice. The gastroprotection and anti-ulcer efficacy of the SIECm (25, 100 and 400mg/kg, p.o.) were tested using acute (acidified ethanol, piroxicam and water restrain stress), and chronic (acetic acid) experimental ulcer models. The plausible mode of action of the SIECm was assessed using gastric secretion, gastric barrier mucus, nitric oxide, and its antioxidant (myeloperoxidase and catalase) effects in mice and rats. The histopathological analyses of the ulcerated tissues as well as the extract's activity on Helicobacter pylori were also investigated. RESULTS: Phytochemical tests indicated the presence of mainly phytosterols, phenolics and flavonoids. The SIECm exhibited no cytotoxic effects on the CHO-k1 cells, and no oral acute toxicity in mice. It prevented against the acute induced ulcerations by enhancing gastroprotection through gastric mucus production, NO modulation, antioxidant, reduced gastric secretion and enhanced chronic ulcers healing process, as shown by reduction/prevention of epithelial and vascular damage, in addition to reduction in leucocyte infiltration. The SIECm however did not exhibit activity against H. pylori. CONCLUSION: The SIECm is safe, contain useful phytochemicals and exhibited significant gastroprotective/anti-ulcer effects. The results justify its folkloric usage, and provided scientific evidence of its potential as a source of new phytodrug to treat gastric ulcers.

Antibacterial mode of action of the hydroethanolic extract of Leonotis nepetifolia (L.) R. Br. involves bacterial membrane perturbations.

ETHNOPHARMACOLOGICAL RELEVANCE: Leonotis nepetifolia (L) R. Br., Lamiaceae, a pantropical shrub, popularly known in Brazil as "cordão-de-frade", "rubim", is reportedly used in Brazilian ethnomedicine as well as in different countries in the treatments of ailments such as infections, inflammations, wounds, stomach disorders, among others. AIM OF THE STUDY: To evaluate its potential cytotoxicity and antibacterial mode of action of the hydroethanolic extract of L. nepetifolia (HELn) leaves, including phytochemical analysis. MATERIALS AND METHODS: The cytotoxicity of HELn was investigated by Alamar blue assay, using CHO-K1 cells. Antibacterial activity of HELn was tested by broth microdilution methods against a panel of bacteria of clinical interest. The mode of action of L. nepetifolia was studied by targeting bacterial membranes. Phytochemical analysis was performed by determining total secondary metabolites with spectrophotometric assays and HPLC. RESULTS: HELn is not cytotoxic in the in vitro evaluation (IC50>200 µg/mL). It demonstrated a good spectrum of antibacterial activity with major activity against Shigella flexneri, Enterococcus faecalis, Staphylococcus aureus and Bacillus subtilis with MIC=6.25 µg/mL, Helicobacter pylori with MIC of 25 µg/mL and Streptococcus pyogenes with MIC of 50 µg/mL. Its mode of action is associated, at least partly, with changes in the permeability of bacterial membranes, as evidenced by the increased entry of hydrophobic antibiotics in Shigella flexneri and intense efflux of K(+) and nucleotide leakage in E. faecalis and Shigella flexneri. In addition, the presence of phenols, flavonoids and carotenoids, described in the literature to possess antibacterial effects, were detected in the composition of HELn, with high phenol content (11.55%), especially the flavonoids (6.47%). CONCLUSION: The results indicate that HELn has low cytotoxicity and potent antibacterial activity. It is bacteriostatic in nature, possibly acting at the level of bacterial membranes, especially on the cytoplasmic membrane and outer membrane, thus supporting its popular use in infectious processes. In addition, the presence of phenols, flavonoids, carotenoids, fatty acids and steroids, described in the literature as possessing antimicrobial activity, were detected in the composition of HELn.