Antioxidant activity of volatile isolates from broccoli and broccoflower obitaned by microwave extraction : bachelor thesis

Abstract

Povrće iz porodice kupusnjača (Brassicaceae) karakterizira prisutnost glukozinolata, skupine sekundarnih biljnih metabolita, čiji razgradni produkti pokazuju izrazito dobru biološku aktivnost. Cilj ovo rada bila izolacija hlapljivih sastojaka iz brokule (Calabrese broccoli) i kineske brokule (Romanesco broccoli). Frakcije su izolirane iz svježeg biljnog materijala korištenjem uređaja za mikrovalnu ekstrakciju (400 W, 98°C, 35 min), a analizirane primjenom tehnike plinske kromatografije s masenom spektrometrijom (GC- MS). Frakcijama je testirana antioksidacijska aktivnost korištenjem različitih metoda: sposobnost hvatanja molekula slobodnog radikala DPPH (2,2-difenil-1-pikrilhidrazil), Briggs-Rauscher oscilacijskom metodom i metodom određivanja redukcijske aktivnosti FRAP (engl. Ferric Reducing Antioxidant Power). GC-MS tehnika je pokazala da je dominantan sumporov spoj koji je produkt degradacije u svim izolatima bio dimetil trisulfid (nastaje raspadom S-metilcistein sulfoksida). Najveća koncentracija ovog spoja određena je u frakciji brokule (0,74%) koja je ujedno pokazala i najbolju antioksidacijsku aktivnost primjenom svih korištenih metoda.The vegetable from the Brassicaceae plant family is characterized by the presence of glucosinolates, a group of secondary plant metabolites, whose degradation products show significant biological activity. The aim of this study was the isolation of the volatiles from two Brassica oleracea species: broccoli (Calabrese broccoli) and broccoflower (Romanesco broccoli). The flavour and fragrance fractions were collected from fresh plant material using microwave-assisted extraction (400 W, 98°C, 35 min) and analysed by gas chromatography-mass spectrometry (GC-MS). The fractions were tested for antioxidant activity by multiple method approach using free DPPH (2,2-diphenyl-1-picrilhydrazil) scavenging activity, Briggs-Rauscher oscillating reaction and reducing activity determination by FRAP assay (Ferric Reducing Antioxidant Power). The dominant sulfur-containing degradation product in all isolates was dimethyl trisulfide (from degradation of S-methylcysteine sulfoxide). This compound was detected in flavour fraction of broccoli (0.74%) in highest concentration, and that fraction also provided the best antioxidant activity using all applied methods