title: Portuguese propolis disturbs glycolytic metabolism of human colorectal cancer in vitro.
abstract: BACKGROUND
  Propolis is a resin collected by bees from plant buds and exudates, which is further processed through the activity of bee enzymes. Propolis has been shown to possess many biological and pharmacological properties, such as antimicrobial, antioxidant, immunostimulant and antitumor activities. Due to this bioactivity profile, this resin can become an alternative, economic and safe source of natural bioactive compounds.Antitumor action has been reported in vitro and in vivo for propolis extracts or its isolated compounds; however, Portuguese propolis has been little explored. The aim of this work was to evaluate the in vitro antitumor activity of Portuguese propolis on the human colon carcinoma cell line HCT-15, assessing the effect of different fractions (hexane, chloroform and ethanol residual) of a propolis ethanol extract on cell viability, proliferation, metabolism and death.
  
  
  METHODS
  Propolis from Angra do Heroísmo (Azores) was extracted with ethanol and sequentially fractionated in solvents with increasing polarity, n-hexane and chloroform. To assess cell viability, cell proliferation and cell death, Sulforhodamine B, BrDU incorporation assay and Anexin V/Propidium iodide were used, respectively. Glycolytic metabolism was estimated using specific kits.
  
  
  RESULTS
  All propolis samples exhibited a cytotoxic effect against tumor cells, in a dose- and time-dependent way. Chloroform fraction, the most enriched in phenolic compounds, appears to be the most active, both in terms of inhibition of viability and cell death. Data also show that this cytotoxicity involves disturbance in tumor cell glycolytic metabolism, seen by a decrease in glucose consumption and lactate production.
  
  
  CONCLUSIONS
  Our results show that Portuguese propolis from Angra do Heroísmo (Azores) can be a potential therapeutic agent against human colorectal cancer.
authors.affiliation: Life and Health Sciences Research Institute-ICVS, School of Health Sciences, University of Minho, Braga, Portugal.
authors.forename: Isabel
authors.initials: I
authors.lastname: Valença
authors.forename: Filipa
authors.initials: F
authors.lastname: Morais-Santos
authors.forename: Vera
authors.initials: V
authors.lastname: Miranda-Gonçalves
authors.forename: Ana Margarida
authors.initials: AM
authors.lastname: Ferreira
authors.forename: Cristina
authors.initials: C
authors.lastname: Almeida-Aguiar
authors.forename: Fátima
authors.initials: F
authors.lastname: Baltazar
mesh_terms: D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D015179:Colorectal Neoplasms / Q000378:metabolism* / Q000503:physiopathology; D006019:Glycolysis / Q000187:drug effects*; D006801:Humans; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D011174:Portugal; D011429:Propolis / Q000737:chemistry*
chemical_list: D010936:Plant Extracts; D011429:Propolis