Cytotoxicity of Selenium-Enriched Chinese Kale (Brassica oleracea var. alboglabra L.) Seedlings Against Caco-2, MCF-7 and HepG2 Cancer Cells

Background: The Selenium-enriched Chinese kale (Brassica oleracea var. alboglabra L.) seedlings (Se-KS) have been known for its antioxidant activities, however its cytotoxic effects on various cancer cells are yet to be reported. Objective: The objective of this work was to study the cytotoxic effects of Se-KS on Caco-2, MCF-7 and HepG2 cancer cells. Materials and Methods: Freeze-dried seedlings were ground and incubated in 0.1 M citrate phosphate buffer pH 7.0 for 1 h at 37°C and extracted with dichloromethane to obtain total isothiocyanate (ITC) content which was quantified using the 1,2-benzenedithiole (BDT)-based cyclocondensation assay. The extracts from fresh seedlings were used to determine the cytotoxic effect on Caco- 2, MCF-7 and HepG2 cancer cells. Results: Se-KS was found to contain total ITC content at 1.02 mmol/100 g dry weight (DW) which was significantly lower than that of 7-day old broccoli microgreens (1.60 mmol/100 g DW) as reference Cruciferous vegetables. In addition, Se-KS extract exhibited cytotoxic effects in a dose- and time-dependent manners. The lowest IC₅₀ value of 82.83 μg/mL at 72 h was derived from HepG2 cells and the highest IC₅₀ value of 164.00 μg/mL at 72 h was from MCF-7 cells suggesting that the Se-KS extract was most effective against HepG2 cells. Cancer cells showed signs of apoptotic bodies over 72 h and DNA fragmentations at 24 h indicating that the Se-KS extract was able to induce apoptosis in cancer cells in addition to cytotoxic effect. Conclusion: Thus, Se-KS could be a novel source of organo selenium with chemopreventive benefits for functional food development.