engleski

Bioactive volatile sulfur compounds from broccoli and broccoflower obtained by microwave assisted extraction

The Brassicaceae plant family is characterized by the presence of glucosinolates (GLs), a group of secondary plant metabolites, whose degradation products, are of interest because of their biological activities. 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 (MAE) (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. The dominant sulfur-containing degradation product in all isolates was dimethyl trisulfide (from degradation of S-methylcysteine sulfoxide). Its highest content was detected in flavour fraction of broccoli (0.74%) which also provided the best antioxidant activity using all applied methods. Furthermore, the effect of more aggressive MAE treatment (500 W) on broccoli degradation products in comparison to the conventional organic solvent extraction with dichloromethane after maceration for 24 h was also studied. This resulted with detection of few sulfur containing volatiles originating from GL degradation among which erucin nitrile (from glucoerucin) and benzenepropanenitrile (from gluconasturtiin) were detected in the highest amounts, 49.5 and 23.8%, respectively.

Brassica oleracea, glucosinolates, degradation products, MAE, GC-MS.

This research has been fully supported by the Croatian Science Foundation under the project HRZZ-IP-06-2016-1316.