Antioxidant and anticancer activities of broccoli by-products from different cultivars and maturity stages at harvest

Abstract

Many studies on broccoli have analyzed the functional components and their functionality in terms of antioxidant and anticancer activities; however, these studies have focused on the florets of different varieties. Investigation of the functionality of broccoli by-products such as leaves, stems, and leaf stems from different cultivars and harvest dates might be valuable for utilizing waste materials as useful food components. Total phenolics and sulforaphane contents, and antioxidant and anticancer activities were measured in the leaves, leaf stems, and stems of early-maturing (Kyoyoshi), middle-maturing (Myeongil 96), and late-maturing broccoli (SK3-085) at different harvest dates. Total phenolics in the leaves of Kyoyoshi were about 1.8-fold to 12.1-fold higher than those in all of the other cultivars and parts. The sulforaphane content of Kyoyoshi was 2.8-fold higher in the stems than in the florets. Antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and oxygen radical absorbance capacity were highest in Kyoyoshi, followed by Myeongil 96 and SK3-085, most notably in the leaves harvested at the immature stage. Inhibition activity of cell growth against the NCI-H1299 cell lines was highest in the leaves of all cultivars in decreasing order of florets, leaf stems, and stems. The leaves harvested in October (nonflowering stage) had the highest inhibition activity, while those harvested in January (mature broccoli) showed the lowest. The results of this study demonstrate that broccoli leaves and stems contain high levels of total phenolics, and high antioxidant and anticancer activities and can provide opportunities for early-maturing broccoli as functional fresh raw vegetables.

Keywords: antioxidant and anticancer activities; broccoli by-products; sulforaphane; total phenolics.

Fig. 1

Antioxidant activities of 80% methanol extracts from the leaves of broccoli SK3-085 cultivar from different harvest dates. Results are expressed as DPPH radical scavenging activity (□) on the Y₁ axis and ORAC (■) on the Y₂ axis. The values within same property with different letters (a, b) are significantly different at P<0.05 by Duncan’s multiple range tests.

Fig. 2

Anticancer activity of 80% methanol extracts (2 mg/mL) from the leaves of broccoli K3-085 cultivar from different harvest dates. Results are expressed as inhibitory activities of cell growth against NCI-H1299 cell (□) and HT-29 (■) cell lines. The values with different letters in the same cell line are significantly different at P<0.05 by Duncan’s multiple range tests.