title: Evaluation of acute toxicity, antibacterial activity, and mode of action of the hydroethanolic extract of Piper umbellatum L.
abstract: BACKGROUND
  Piper umbellatum L., Piperaceae, is a shrub that grows up to 3m high. It is commonly known as "capeba" or "pariparoba" in Brazil. Tea prepared using the leaves of this plant is employed in the treatment of infections and inflammatory processes in different countries. Approximately 50 compounds, notably from the flavonoid, alkaloid, terpene, and sterol classes, have been isolated from the leaves of Piper umbellatum. To evaluate the acute toxicity, antibacterial activity, and mode of action of the hydroethanolic extract of Piper umbellatum leaves (HEPu).
  
  
  METHODS
  Acute toxicity of HEPu against CHO-K1 cells was evaluated using a cytotoxicity assay with Alamar Blue and that against mice was assessed by the Hippocratic test. Antibacterial activity of HEPu was tested using the broth microdilution method using a panel of clinically relevant bacteria, and the effects of HEPu on the bacterial membrane were analyzed in detail. A preliminary phytochemical analysis based on coloration/precipitation was performed according to procedure described in the literature. Secondary metabolites detected were analyzed and confirmed by thin layer chromatography (TLC), spectrophotometry, and high performance liquid chromatography (HPLC).
  
  
  RESULTS
  Piper umbellatum did not appear to be toxic in the in vitro (IC50>200 µg/mL) cytotoxicity test. When administered in vivo at doses up to 2000 mg/kg p.o., HEPu did not cause any signs or symptoms of toxicity in mice. It demonstrated a good spectrum of antibacterial activity and its mode of action appeared to be associated with changes in the permeability of bacterial membranes; it led to increased entry of hydrophobic antibiotics, efflux of K(+), and nucleotide leakage. Preliminary phytochemical analysis revealed the presence of flavonoids, alkaloids, terpenes, and sterols in the extract. Spectrophotometric and HPLC analysis revealed the presence of the flavonoids rutin and quercetin.
  
  
  CONCLUSIONS
  In summary, HEPu has antibacterial activity and low acute toxicity in vitro and in vivo. Its mode of action appears to be associated with changes in the permeability of the bacterial cell wall and cytoplasmic membrane, which can at least be partly attributed to the flavonoids present in the extract.
authors.affiliation: Department of Basic Sciences in Health, Faculty of Medicine, Federal University of Mato Grosso (UFMT), Av. Fernando Correa da Costa, no. 2367, Coxipó, Cuiabá, Mato Grosso 78060-900, Brazil.
authors.forename: Iberê Ferreira
authors.initials: IF
authors.lastname: da Silva
authors.affiliation: Department of Basic Sciences in Health, Faculty of Medicine, Federal University of Mato Grosso (UFMT), Av. Fernando Correa da Costa, no. 2367, Coxipó, Cuiabá, Mato Grosso 78060-900, Brazil.
authors.forename: Ruberlei Godinho
authors.initials: RG
authors.lastname: de Oliveira
authors.affiliation: Federal University of Tocantins, Faculty of Food Engineering, Agroenergy Undergraduate Program, Av. NS 15, Block number III, 26 Room, Palmas, Tocantins 77020-210, Brazil.
authors.forename: Ilsamar
authors.initials: I
authors.lastname: Mendes Soares
authors.affiliation: Federal University of Tocantins, Faculty of Food Engineering, Agroenergy Undergraduate Program, Av. NS 15, Block number III, 26 Room, Palmas, Tocantins 77020-210, Brazil.
authors.forename: Tarso
authors.initials: T
authors.lastname: da Costa Alvim
authors.affiliation: Federal University of Tocantins, Faculty of Food Engineering, Agroenergy Undergraduate Program, Av. NS 15, Block number III, 26 Room, Palmas, Tocantins 77020-210, Brazil; Federal University of Tocantins, Faculty of Medicine, Av. NS15, BALA Block, 11 C Room, Palmas, Tocantins 77020-210, Brazil.
authors.forename: Sérgio
authors.initials: S
authors.lastname: Donizeti Ascêncio
authors.affiliation: Department of Basic Sciences in Health, Faculty of Medicine, Federal University of Mato Grosso (UFMT), Av. Fernando Correa da Costa, no. 2367, Coxipó, Cuiabá, Mato Grosso 78060-900, Brazil.. Electronic address: domingos.tabajara@pq.cnpq.br.
authors.forename: Domingos Tabajara
authors.initials: DT
authors.lastname: de Oliveira Martins
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D000431:Ethanol; D008297:Male; D051379:Mice; D008826:Microbial Sensitivity Tests; D031701:Piper / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity*; D011188:Potassium / Q000378:metabolism; D014867:Water
chemical_list: D000900:Anti-Bacterial Agents; D010936:Plant Extracts; D014867:Water; D000431:Ethanol; D011188:Potassium
keywords: Antibacterial activity; Flavonoids; Hydroethanolic extract; Mode of action; Piper umbellatum