title: Application of crude extract of kohlrabi (Brassica oleracea gongylodes) as a rich source of peroxidase in the spectrofluorometric determination of hydrogen peroxide in honey samples.
abstract: Crude extract of kohlrabi (Brassica oleracea gongylodes) was prepared by a simple procedure and its enzymatic activity and total protein concentration were determined. It was found that this crude extract is a rich source of peroxidase (POx) and has high specific activity. Cross-linked polyvinylpyrrolidone was used as a stabilizer in the preparation of the crude extract. The POx activity of kohlrabi crude extract did not vary for at least 2 months when deoxygenated and stored at 4 degrees C. This extract was applied for the spectrofluorometric determination of hydrogen peroxide using homovanillic acid as a fluorogenic substrate. POx catalyzes the hydrogen peroxide oxidation of homovanillic acid to produce a dimer which shows strong fluorescence at 420 nm with excitation at 312 nm. In the optimum conditions, the calibration graph for hydrogen peroxide was linear up to 190 ng mL(-1), with a detection limit of 4.4 ng mL(-1). The relative standard deviation (RSD) was 1.48% for 50 ng mL(-1) hydrogen peroxide. The proposed method was successfully applied to the determination of hydrogen peroxide in honey. The concentration-time profile of H2O2 produced upon dilution of honey was studied and H2O2 contents of some different honeys from various areas of Iran were determined.
authors.affiliation: Department of Analytical Chemistry, Faculty of Chemistry, University of Tabriz, Iran. manzoori@tabrizu.ac.ir
authors.forename: Jamshid L
authors.initials: JL
authors.lastname: Manzoori
authors.forename: Mohammad
authors.initials: M
authors.lastname: Amjadi
authors.forename: Maghsood
authors.initials: M
authors.lastname: Orooji
mesh_terms: D001937:Brassica / Q000378:metabolism*; D002021:Buffers; D002384:Catalysis; D006719:Homovanillic Acid / Q000032:analysis; D006722:Honey; D006861:Hydrogen Peroxide / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007492:Iran; D007700:Kinetics; D009195:Peroxidase / Q000032:analysis / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D002021:Buffers; D010936:Plant Extracts; D014867:Water; D006861:Hydrogen Peroxide; D009195:Peroxidase; D006719:Homovanillic Acid