title: Free radical scavenging activities of guava extract in vitro.
abstract: BACKGROUND
  Psidium guajava (guava) is used in folk medicine in treating diverse human ailments. The therapeutic benefit of medicinal plants is often attributed to their antioxidant properties.
  
  
  OBJECTIVE
  This study evaluated the radical scavenging potentials of ethanolic extract of Psidium guajava (EEPG) in vitro.
  
  
  METHODS
  Radical scavenging potential of EEPG was determined by assessing its reducing power, extent of LPO, NO, H2O2, DPPH inhibition and TEAC.
  
  
  RESULTS
  AAPH-induced LPO was significantly (P < 0.05) inhibited by 56.5%, 65.3%, 55.1%, 54.4%, 53.1%, at 25-400 micro/g of EEPG. The reference drug, catechin at 50 microg, produced 39.5% inhibition of LPO induced by AAPH respectively with respect to control. EEPG produced significant (p < 0.05) inhibition of deoxyribose degradation at 100-800 microg concentrations by 30.9% (p < 0.01), 42.5%, 55.7%, 72.8% (p < 0.001) respectively with respect to control. Catechin also show potency, producing 55.5% at 25 microg (p < 0.001). Furthermore, the antioxidant activity of EEPG ranged from 763.08 to 1206.2 micromol trolox equivalent in the TEAC assay at 50-200 microg (p < 0.001) and 24.62 to 14.77 micromol trolox equivalent at 800-2000 microg (p < 0.001). Catechin exhibited a TEAC value of 2338.5 micromol trolox equivalent (p < 0.001). EEPG exhibited maximum radical scavenging activities of 30.1% on NO radical (p < 0.01), 98.72% on H2O2 (p < 0.001), at 50 microg and 70.45% on DPPH radical (p < 0.001) at 100 microg. EEPG also demonstrated marked reducing power, increasing absorbance values from 0.24 +/- 0.01 to 1.86 +/- 0.20 at 25-160 microg. The reducing power of EEPG at 200 microg (0.41 +/- 0.07) almost compares with that of catechin at 50 microg (0.45 +/- 0.028).
  
  
  CONCLUSIONS
  These results demonstrate that the ethanolic extract of Psidium guajava (EEPG) exhibited significant free radical scavenging and antioxidant activities in vitro.
authors.affiliation: Drug Metabolism and Toxicology Unit, Department of Biochemistry, Faculty of Basic Medical Sciences, College of Medicine, University of Ibadan, Ibadan, Nigeria.
authors.forename: A
authors.initials: A
authors.lastname: Adesida
authors.forename: E O
authors.initials: EO
authors.lastname: Farombi
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D002392:Catechin / Q000494:pharmacology; D002839:Chromans / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000032:analysis / Q000494:pharmacology; D006801:Humans; D010084:Oxidation-Reduction / Q000187:drug effects*; D018384:Oxidative Stress / Q000187:drug effects; D010851:Picrates / Q000494:pharmacology; D010936:Plant Extracts / Q000032:analysis / Q000494:pharmacology; D031647:Psidium
chemical_list: D000975:Antioxidants; D002839:Chromans; D016166:Free Radical Scavengers; D010851:Picrates; D010936:Plant Extracts; D002392:Catechin; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid