Original research articleAssessment of glucosinolates, antioxidative and antiproliferative activity of broccoli and collard extracts

•Collard leaves contain more phenolics than broccoli florets.•Total content of glucosinolates was higher in broccoli extracts.•Collard extracts exhibited higher antioxidant capacity than broccoli extracts.•Extracts obtained from blanched vegetables possess the highest antitumour activity.•Protective effect of vegetable extracts on oxidative-stressed cells was observed.

Natural compounds isolated from vegetables have protective and disease-preventing potential for the development of functional food. This study investigates the in vitro antioxidant capacity, total polyphenol and total flavonoid content, glucosinolate and glucosinolate degradation products of broccoli and collard extracts. In vitro antitumor activities on two human tumour cell lines (MCF-7 and HeLa) were studied. Broccoli and collard extracts were extracted from fresh, blanched and boiled broccoli florets and collard leaves. The Oxygen Radical Absorbance Capacity (ORAC) assay revealed that collard extracts exhibited higher antioxidant capacity than broccoli extracts. Total polyphenol and total flavonoid contents were also higher in collard extracts. The extracts were compared for the contents of total glucosinolates, indol glucosinolates and aliphatic glucosinolates. Glucoraphanin was the predominant compound in total glucosinolate content, followed by glucobrassicin and neoglucobrassicin (95.97 μmol 100 g−1 fresh weight (fw), 85.42 μmol 100 g−1 fw and 82.12 μmol 100 g−1 fw, respectively) in broccoli extracts; while in collard extracts, the major glucosinolate was glucobrassicin (80.33 μmol 100 g−1 fw), followed by glucoiberin (67.50) μmol 100 g−1 fw and sinigrin (21.91 μmol 100 g−1 fw). The strongest antiproliferative effect was observed in extracts obtained by blanching. The present study established that the extracts that were examined possess antioxidant and promising antitumour activities.