Sastav polifenola i metilksantina u vodenim i metanolnim ekstraktima različitih kakao-proizvoda

master's thesis

• Title (english): The composition of polyphenols and methylxantines in qqueous and methanolic extracts of various cocoa products
• Author: Ana Belščak
• Mentor: Draženka Komes (mentor)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Food Engineering); (Laboratory for Chemistry and Technology of Carbohydrates and Confectionery Products); Zagreb
• Defense date and country: 2007-07-12, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Food Technology

Abstract

Posljednjih nekoliko godina veliko zanimanje znanstvenih istraživanja usmjereno je na kakao-proizvode, kao bogate izvore različitih biološki aktivnih spojeva, posebno polifenola i metilksantina, koji zbog izražene antioksidacijske aktivnosti imaju pozitivan utjecaj na ljudsko zdravlje. Cilj ovog rada bio je analizirati sastav polifenola i metilksantina u različitim kakaoproizvodima te odrediti njihovu antioksidacijsku aktivnost. Uspoređena je učinkovitost otapala za ekstrakciju (70%-tni metanol i voda) te je ispitan utjecaj kiselinske hidrolize ekstrakata na udjel polifenola i metilksantina. Udjeli ukupnih fenola, ukupnih neflavonoida i flavonoida, ukupnih flavan- 3-ola i ukupnih procijanidina određeni su spektrofotometrijskim metodama, dok je primjenom tekućinske kromatografije visoke djelotvornosti (HPLC-PDA) određen udjel pojedinačnih polifenola i metilksantina. Primjenom NMR tehnike određen je udjel čvrste faze kakao-proizvoda. Najveći udjel ukupnih fenola, flavonoida, flavan-3-ola i procijanidina određen je u kakao-masi i kakao-prahu, dok se u ostalim kakao-proizvodima udjeli navedenih fenolnih spojeva smanjuju proporcionalno smanjenju udjela kakao-dijelova. Veći udjeli fenolnih spojeva određeni su u metanolnim, u odnosu na vodene ekstrakte, dok su u hidroliziranim ekstraktima ti udjeli najmanji. Iz skupine flavan-3-ola najzastupljeniji spojevi su (−)-epikatehin (EC) i (−)-galokatehin (GC), iz skupine fenolnih kiselina galna kiselina, dok je teobromin najznačajniji metilksantin. Antioksidacijska aktivnost ispitana je primjenom tri metode: reakcijom s 1,1-difenil-2-pikrilhidrazil radikalom (DPPH metoda) i 2,2`-azinobis( 3-etilbenzotiazolin-6-sulfonska kiselina) radikalom (ABTS metoda) te reakcijom s željezo(III)- tripiridiltirazin (Fe3+-TPTZ) kompleksom (FRAP metoda).

Abstract (english)

In recent years, cocoa products have been extensively investigated, due to their high content of biologically active compounds, such as polyphenols and methylxantines, which have been shown to posses beneficial effects on human health, owing to their strong antioxidant activity. The aim of this study was to determine the phenolic and methylxantine composition, as well as the antioxidant activity of different cocoa products. In order to compare the effectiveness of extraction solvent, and to determine the effect of acidic hydrolisis on polyphenol and methylxantine contents, 70% aqueous methanol and water were used for the extraction and the obtained extracts were then hydrolized. The content of total phenols, total flavonoids, total flavan-3-ols and total procyanidins was determined by using spectrophotometric methods, while the composition of individual phenolic compounds and methylxantines was determined by using high performance liquid chromatography (HPLC-PDA). The highest content of total phenols as well as total flavonoids, flavan-3-ols and procyanidins was determined in cocoa liquor and cocoa powder, while in other cocoa products the total content of these phenolic compounds decreased proportionally with the decrease in the amount of cocoa solids. Higher results were obtained when methanol was used for the extraction (instead of water), while the hydrolisis procedure resulted with lower contents of phenolic compounds and methylxantines. The most abundant flavan-3-ols were (−)-epicatechin (EC) and (−)-gallocatechin (GC), whereas gallic acid was the most abundant phenolic acid. Theobromine is the predominant methylxantine in cocoa products. The extracts were screened for their potential antioxidant activities using three different radical scavenging methods: reactions with 1,1-diphenyl-2-picrylhydrazyl radical (DPPH assay), with 2,2`-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical (ABTS assay) and Ferric reducing antioxidant power (FRAP assay).

• Keywords: antioksidacijska aktivnost; HPLC; kakao-proizvodi; metilksantini; polifenoli
• Keywords (english): antioxidant activity; cocoa products; HPLC; methylxantines; polyphenols
• Language: croatian
• URN:NBN: urn:nbn:hr:159:155394
• Study programme: Title: Food Technology; specializations in: Food Engineering; Course: Food Engineering; Study programme type: university; Study level: graduate; Academic / professional title: diplomirani inženjer prehrambene tehnologije; smjer prehrambeno inženjerstvo (diplomirani inženjer prehrambene tehnologije; smjer prehrambeno inženjerstvo)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2017-09-06 08:52:11