title: Inhibitory effect of Clitoria ternatea flower petal extract on fructose-induced protein glycation and oxidation-dependent damages to albumin in vitro.
abstract: BACKGROUND
  The accumulation of advanced glycation end products (AGEs) in body tissue has been implicated in the progression of age-related diseases. Inhibition of AGE formation is the imperative approach for alleviating diabetic complications. Clitoria ternatea extract (CTE) has been demonstrated to possess anti-diabetic activity. However, there is no scientific evidence supporting its anti-glycation activity. The objective of this study was to determine the inhibitory effect of CTE on fructose-induced formation of AGEs and protein oxidation. Antioxidant activity of CTE was also assessed by various methods.
  
  
  METHODS
  The aqueous extract of CTE (0.25-1.00 mg/ml) was measured for the content of total phenolic compounds, flavonoid, and anthocyanin by Folin-Ciocalteu assay, AlCl3 colorimetric method, and pH differential method, respectively. The various concentrations of CTE were incubated with BSA and fructose at 37°C for 28 days. The formation of fluorescent AGEs, the level of fructosamine, protein carbonyl content, and thiol group were measured. The in vitro antioxidant activity was measured by the 1,1-diphenyl 2-picrylhydrazyl (DPPH) scavenging activity, trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant power (FRAP), hydroxyl radical scavenging activity (HRSA), superoxide radical scavenging activity (SRSA), and ferrous ion chelating power (FICP).
  
  
  RESULTS
  The results demonstrated that the content of total phenolics, flavonoids and total anthocyanins in CTE was 53 ± 0.34 mg gallic acid equivalents/g dried extract, 11.2 ± 0.33 mg catechin equivalents/g dried extract, and 1.46 ± 0.04 mg cyanidin-3-glucoside equivalents/g dried extract, respectively. Moreover, CTE (0.25-1.00 mg/ml) significantly inhibited the formation of AGEs in a concentration-dependent manner. CTE also markedly reduced the levels of fructosamine and the oxidation of protein by decreasing protein carbonyl content and preventing free thiol depletion. In the DPPH radical scavenging activity and SRSA, CTE had the IC50 values of 0.47 ± 0.01 mg/ml and 0.58 ± 0.04 mg/ml. Furthermore, the FRAP and TEAC values of CTE were 0.38 ± 0.01 mmol FeSO4 equivalents/mg dried extract and 0.17 ± 0.01 mg trolox equivalents/mg dried extract. However, CTE showed weak scavenging activity on hydroxyl radical and a weak antioxidant iron chelator.
  
  
  CONCLUSIONS
  The results showed that CTE has strong antiglycation and antioxidant properties and might have therapeutic potentials in the prevention of AGE-mediated diabetic complications.
authors.affiliation: Department of Pharmacology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, 10330, Thailand. poraminshayarat@gmail.com.|Program in Veterinary Biosciences, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, 10330, Thailand. poraminshayarat@gmail.com.|Research Group of Herbal Medicine for Prevention and Therapeutic of Metabolic Diseases, Chulalongkorn University, Bangkok, 10330, Thailand. poraminshayarat@gmail.com.
authors.forename: Poramin
authors.initials: P
authors.lastname: Chayaratanasin
authors.affiliation: Department of Biological Sciences, Florida International University, Miami, FL, 33199, USA. barbieri@fiu.edu.|Biomolecular Sciences Institute, Florida International University, Miami, FL, 33199, USA. barbieri@fiu.edu.|Fairchild Tropical Botanic Garden, 10901 Old Cutler Road, Coral Gables, FL, 33156, USA. barbieri@fiu.edu.
authors.forename: Manuel Alejandro
authors.initials: MA
authors.lastname: Barbieri
authors.affiliation: Department of Pharmacology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, 10330, Thailand. nipattra@gmail.com.
authors.forename: Nipattra
authors.initials: N
authors.lastname: Suanpairintr
authors.affiliation: Research Group of Herbal Medicine for Prevention and Therapeutic of Metabolic Diseases, Chulalongkorn University, Bangkok, 10330, Thailand. Sirichai.a@chula.ac.th.|Department of Nutrition and Dietetics, Faculty of Allied Health Sciences, Chulalongkorn University, Bangkok, 10330, Thailand. Sirichai.a@chula.ac.th.
authors.forename: Sirichai
authors.initials: S
authors.lastname: Adisakwattana
mesh_terms: D000418:Albumins / Q000378:metabolism*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D031292:Clitoria / Q000737:chemistry*; D005419:Flavonoids / Q000032:analysis / Q000494:pharmacology; D035264:Flowers / Q000737:chemistry; D005632:Fructose / Q000009:adverse effects*; D017127:Glycation End Products, Advanced / Q000037:antagonists & inhibitors*; D006031:Glycosylation; D066298:In Vitro Techniques; D010084:Oxidation-Reduction; D010636:Phenols / Q000032:analysis / Q000494:pharmacology; D008517:Phytotherapy; D010936:Plant Extracts / Q000494:pharmacology*; D050050:Protein Carbonylation / Q000187:drug effects*; D012710:Serum Albumin, Bovine / Q000378:metabolism
chemical_list: D000418:Albumins; D000975:Antioxidants; D005419:Flavonoids; D017127:Glycation End Products, Advanced; D010636:Phenols; D010936:Plant Extracts; D012710:Serum Albumin, Bovine; D005632:Fructose