Kinetika reakcija kvercetina i DPPH radikala

master's thesis

• Title (english): Kinetics of quercetin and DPPH radical reaction
• Author: Dorotea Murković
• Mentor: Cvijeta Jakobušić Brala (mentor)
• Committee member: Cvijeta Jakobušić Brala (predsjednik povjerenstva)
• Committee member: Monika Barbarić (član povjerenstva)
• Committee member: Viktor Pilepić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Pharmacy and Biochemistry; (Department of physical chemistry); Zagreb
• Defense date and country: 2022-05-24, Croatia
• Scientific / art field, discipline and subdiscipline: BIOMEDICINE AND HEALTHCARE; Pharmacy; Pharmacy

Abstract

Kvercetin spada u podskupinu flavonola te mu se pripisuje niz bioloških učinaka: antioksidativni, antikarcinogeni,
antialergijski, protuupalni i drugi. Reakcije flavonoida i DPPH• uobičajeno se prate tako što se mjeri smanjenje
apsorbancije na valnoj duljini koja odgovara maksimumu DPPH•. Prema novijoj literaturi (Foti i sur., 2011) smanjenje
apsorbancije u vidljivom području spektra nije povezano izravno s redukcijom DPPH•, te reakcijska otopina, osim
početno, ne sadrži DPPH•. U ovom je diplomskom radu ispitana kinetika reakcije kvercetina i DPPH• radikala u smjesi
otapala dioksan-voda (0,99:0,01 v/v) te u metanolu. Na temelju izmjerene ovisnosti konstante brzine reakcije pseudoprvog reda o koncentraciji kvercetina određena je konstanta brzine reakcije kvercetina i DPPH• u dioksanu, koja iznosi
4,38 mol-1dm3 s -1. Konstante brzine određene na 525 nm i 620 nm su približno iste, iako su odstupanja u izmjerenim
vrijednostima na 525 nm znatno veća u odnosu na 620 nm. Određena je konstanta brzine reakcije kvercetina i DPPH• u
metanolu čija vrijednost iznosi 469 mol-1dm3 s -1. U metanolu nisu utvrđena odstupanja u izmjerenim vrijednostima kao
u dioksanu. Na temelju izmjerene ovisnosti konstante brzine reakcije pseudo-prvog reda o koncentraciji kvercetina u
otapalu dioksan-D2O određena je konstanta brzine reakcije kD koja iznosi 0,568 mol-1dm3 s -1 te kinetički izotopni efekt
koji iznosi 7,71. Ovi podaci nisu prethodno pronađeni u literaturi te su po prvi puta određeni u ovom diplomskom radu.
Za usporedbu su provedena i kinetička i HPLC mjerenja reakcije katehina i DPPH•. Određena je konstanta brzine
reakcije katehina i DPPH• u metanolu koja iznosi 2,70 mol-1dm3 s -1. HPLC analizom je potvrđeno da je tijekom cijelog
perioda u kojemu se prati smanjenje apsorbancije u vidljivom dijelu spektra u reakcijskoj otopini prisutan DPPH• (u
reakciji kvercetina i DPPH• te u reakciji katehina i DPPH•).

Abstract (english)

Quercetin is a flavonol, a subclass of flavonoids that has numerous pharmacological uses due to its antioxidant,
anticarcinogenic, antiallergic and anti-inflammatory properties. The reaction of flavonoids and DPPH• are commonly
monitored by measuring the decrease in absorption at the wavelength corresponding to the maximum DPPH•. According
to new literature (Foti et al., 2011), the decrease in absorption in the visible region of the spectrum is not directly related
to the reduction of DPPH • and the reaction solution, except initially, does not contain the DPPH radical. In this thesis,
the reaction kinetics of quercetin and DPPH• in a solvent mixture of dioxane-water (0,99:0,01 v/v) and methanol were
investigated. Based on the measured dependence of the pseudo-first order reaction rate constant on the quercetin
concentration, the reaction rate constant of quercetin and DPPH • in dioxane was determined to be 4,38 mol-1dm3s-1.
The rate constants determined at 525 nm and 620 nm are approximately the same, although the deviations in the
measured values at 525 nm are significantly larger compared to 620 nm. The reaction rate constant of quercetin and
DPPH• in methanol with a value of 469 mol-1dm3s-1 was determined. No deviations in the measured values were found
in methanol as in dioxane. Based on the measured dependence of the pseudo-first order reaction rate constant on the
quercetin concentration in the solvent dioxane-D2O, a reaction rate constant kD of 0,568 mol-1dm3s-1 and a kinetic
isotopic effect of 7,71 were determined. These data were not previously found in the literature and were determined for
the first time in this thesis. Both kinetic and HPLC measurements of catechin and DPPH • reactions were performed for
comparison. The rate constant of the reaction of catechins and DPPH• in methanol was determined to be 2,70 mol1dm3s-1. HPLC analysis confirmed that DPPH• (in the reaction of quercetin and DPPH • and the reaction catechin and
DPPH •) was present in the reaction solution during the whole period in which the decrease in absorption was monitored
in the visible part of the spectrum.

• Keywords: antioksidansi; antioksidativna aktivnost; DPPH; kvercetin; konstanta brzine reakcije; kinetički izotopni efekt; HPLC; UV-VIS
• Keywords (english): antioxidants; antioxidant activity; DPPH; quercetin; rate constant; kinetic isotope effect; HPLC; UV-VIS
• Language: croatian
• URN:NBN: urn:nbn:hr:163:707067
• Study programme: Title: Pharmacy; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: magistar/magistra farmacije (magistar/magistra farmacije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2022-05-31 10:09:31