Vpliv priprave vzorca na določanje antioksidativne učinkovitosti medu

Žlavs, Katarina (avtor), Korošec, Mojca (mentor)

Med je zaradi vsebnosti polifenolov ter drugih bioaktivnih spojin znan po svoji antioksidativni učinkovitosti in se v ljudski medicini uporablja zaradi ugodnih učinkov na zdravje. Antioksidativno učinkovitost medu in vitro določamo s spektrofotometričnimi metodami, vendar različna priprava vzorcev lahko vpliva tudi na razlike med rezultati. Namen diplomskega dela je ugotoviti vpliv priprave vzorca na določanje antioksidativne učinkovitosti medu. Cilj je bil določiti skupne fenolne spojine, flavonoide in antioksidativno učinkovitost v vzorcih medu različnega botaničnega izvora, različnih tudi v barvi, pripravljenih na tri različne načine. V analizo smo vključili akacijev, cvetlični in gozdni med, jim izmerili vsebnost vode (refraktometrično), električno prevodnost (konduktometrično) ter barvo s kromametrom. Za spektrofotometrične analize smo vzorce pripravili na tri načine; med smo raztopili v 1) vodi, 2) 70 % etanolu ali 3) nakisani vodi in zatem ekstrahirali na trdni fazi (SPE), fenolne spojine pa raztopili v mešanici metanol/acetonitril. Glede na rezultate analiz smo ugotovili pozitivno korelacijo med vsebnostjo fenolnih spojin in antioksidativno učinkovitostjo, vrednosti teh parametrov pa so povezane z botaničnim izvorom medu, njegovo barvo in električno prevodnostjo. Analize vsebnosti fenolnih spojin s Folin-Ciocalteujevim reagentom, flavonoidov z AlCl3 ter antioksidativne učinkovitosti po metodi DPPH so pokazale, da priprava vzorca vpliva na analizirane vrednosti. Vodni in etanolni ekstrakti so pri vseh analizah pokazali višje vrednosti kot vzorci ekstrahirani po SPE. Takšni rezultati so posledica prisotnih sladkorjev in drugih reducirajočih spojin v medu, ki motijo analizo. Ugotovili smo, da najbolj zanesljive rezultate dajejo vzorci, pripravljeni z ekstrakcijo na trdni fazi, še posebej pri določanju skupnih flavonoidov.

• Jezik: Slovenski jezik
• Ključne besede: med, antioksidativna učinkovitost, fenoli, flavonoidi, priprava vzorca
• Vrsta gradiva: Diplomsko delo/naloga
• Tipologija: 2.11 - Diplomsko delo
• Organizacija: BF - Biotehniška fakulteta
• Založnik: [K. Žlavs]
• Leto izida: 2018
• PID: 20.500.12556/RUL-103127
• UDK: 638.162:577.1:543.42.05
• COBISS.SI-ID: 4955256
• Datum objave v RUL: 14.09.2018

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: The effect of the sample preparation on honey antioxidant activity determination

Izvleček

Due to its richness in phenolic compounds and other bioactive substances, honey is well-known for its antioxidant ability and since it has beneficial effect od health, it is used in folk medicine. Antioxidant activity is determined with in vitro assays, using spectrophotometrics methods. However, the sample preparation can lead to different results of the analysis. Thus, in this bachelor thesis, we aim to research the effect of the sample preparation on honey antioxidant activity determination. Our aim was to determine total phenolic and total flavonoid content in the honey samples and their antioxidant activity. The samples that we analysed were of different botanical origin, and of different of colours, prepaired on three different ways. The analyses were carried on the samples od acacia, floral and forest types of honey. We measured their water content (refractometric assay), electric conductivity (conductometric assay) and colour (with chromameter). For the spectrophotometric assays we prepaired the honey samples in three different ways: by dissolving honey in 1) water, 2) 70% ethanol or 3) acidified water, then extracted on solid phase (SPE) and eluted phenolic fractions in methanol/acetonitrile solution. The results revealed positive correlation between phenolics content and antioxidative ability. The values of these parameters are linked to the botanical origin of honey, its colour and its electric contuctivity. The analyses od the total phenolic content, using Folin-Ciocalteu reagent, of the total flavonoids content using aluminium chloride reagent as well as the analysis of the antioxidant activity using the DPPH reagent, revealed the effect of the sample preparation on measured values. Water and ethanol extracts resulted in higher values than the samples, extracted on SPE. This is due to the presence of sugar and other reducing compounds in honey, which hamper analysis. Thus, we discovered that the samples, that were prepaired by using the solid-phase extraction method produce the most reliable results, especially when the determination of the total flavonoid content is concerned.

• Ključne besede: honeys, antioxidant activity, phenolics, flavonoids, sample preparation