Analysis and Antioxidant Activity of Extracts from Broccoli (Brassica oleracea L.) Sprouts

Samples prepared from fresh broccoli (Brassica oleracea L.) sprouts by water distillation or freeze-drying were examined for antioxidant activity using three assays. All samples exhibited dose-dependent antioxidant activity. The antioxidant activity ranged from 74.48 ± 0.46% (less volatile sample) to 93.2 ± 0.2% (dichloromethane extract sample) at the level of 500 μg/mL. Both dichloromethane extract samples from a water distillate of broccoli sprouts and freeze-dried broccoli sprouts showed potent antioxidant activity, which was comparable to that of BHT. Among the 43 compounds positively identified by gas chromatography-mass spectrometry, 5-methylthiopentylnitrile (31.64 μg/g) was found in the greatest concentration, followed by 4-methylthiobutylisothiocyanate (14.55 μg/g), 4-methylthiobutylnitrile (10.63 μg/g), 3-methylthiopropylisothiocyanate (3.00 μg/g), and 4-methylpentylisothiocyanate (2.48 μg/g). These isothiocyanates are known to possess antioxidant properties. Possible phenolic antioxidants found are 4-(1-methylpropyl)phenol (0.012 μg/g), 4-methylphenol (0.159 μg/g), and 2-methoxy-4-vinylphenol (0.009 μg/g). The present study demonstrates that broccoli sprouts are a good source of natural antioxidants.