title: Analytical methodology optimization to estimate the content of non-flavonoid phenolic compounds in Argentine propolis extracts.
abstract: BACKGROUND
  Traditionally, the content of total phenolics (flavonoid phenolics (FP) and non-flavonoid phenolics (NFP)) and flavonoids (flavone/flavonol and flavonone/dihydroflavonol) in propolis has been determined by different methodologies. Until now, the percentage of total phenolic (TP) compounds that corresponds to FP and NFP, expressed in the same units by a spectrophotometric method, has not been determined.
  
  
  OBJECTIVE
  The current study proposes a quick and simple methodology that separates FP and NFP in propolis samples and determines TP, FP, and NFP by the same method.
  
  
  METHODS
  Propolis samples from five Argentine provinces (Tucumán, Santiago del Estero, Salta, Misiones, and Jujuy) were used. Extraction of TP from the propolis samples was carried out by maceration with 80% ethanol and quantified by Folin-Ciocalteu reagent (FC-R). Then, FP was precipitated with formaldehyde in acid medium. After centrifugation, NFP were determined in the supernatant using FC-R. FP content was calculated as the difference between the content of TP and NFP. The method was also validated using commercial flavonoids and chalcones.
  
  
  RESULTS
  FP recovery in all experiments was between 85.95% and 98.29%. Propolis from Tucumán had significantly higher amounts of total phenols than propolis from other provinces. SE5 showed higher content of FP (81.52%) followed by SA1 (74.75%). The propolis from TUC4, SA4, SE3, and MI showed the lowest FP content and highest content of NFP.
  
  
  CONCLUSIONS
  This method provides a simple, reliable, and specific spectrophotometric assay to estimate the content of NFP, FP, and TP in propolis samples.
authors.affiliation: Instituto de Química del Noroeste Argentino (INQUINOA) , CONICET, Tucumán , Argentina .
authors.forename: María Inés
authors.initials: MI
authors.lastname: Isla
authors.forename: Ana
authors.initials: A
authors.lastname: Salas
authors.forename: Fatima C
authors.initials: FC
authors.lastname: Danert
authors.forename: Iris Catiana
authors.initials: IC
authors.lastname: Zampini
authors.forename: Roxana Mabel
authors.initials: RM
authors.lastname: Ordoñez
mesh_terms: D002855:Chromatography, Thin Layer; D005419:Flavonoids / Q000032:analysis* / Q000302:isolation & purification; D007202:Indicators and Reagents / Q000737:chemistry; D008982:Molybdenum / Q000737:chemistry; D010636:Phenols / Q000032:analysis* / Q000302:isolation & purification; D011429:Propolis / Q000737:chemistry*; D013053:Spectrophotometry; D017973:Tungsten Compounds / Q000737:chemistry
chemical_list: D005419:Flavonoids; C029556:Folin's phenol reagent; D007202:Indicators and Reagents; D010636:Phenols; D017973:Tungsten Compounds; D008982:Molybdenum; D011429:Propolis
keywords: Bee glue; flavonoid phenolic precipitation; total phenolic compounds content