Betalain and Betaine Composition of Greenhouse- or Field-Produced Beetroot (Beta vulgaris L.) and Inhibition of HepG2 Cell Proliferation

The composition of betalain, red or yellow pigments, and betaine (trimethylglycine or glycinebetaine) of nine beetroot ( Beta vulgaris L.) cultivars produced in the greenhouse or field was studied. Inhibition of HepG2 cell proliferation by betanin and betaine was also tested. Four predominant betalains, two betacyanins (betanin and isobetanin) and two betaxanthins (vulgaxanthin I and miraxanthin V), were isolated and quantified. Betanin and vulgaxanthin I were the major compounds in red and yellow beetroot extracts, respectively, and they comprised >90% of the betalain content in the tested cultivars. The total betalain content of beetroots produced from the field was between 650 and 800 μg/g fresh weight, approximately 25% higher than those from the greenhouse. The betaine content of the beetroot grown in the field was between 3.0 and 4.8 mg/g fresh weight, approximately 20% higher than in plants from the greenhouse. There was great variation among the cultivars with respect to their contents of betalains and betaine. In vitro cancer cell cytotoxicity was evaluated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay on HepG2 cells after exposure to betanin and betaine at concentrations ranging from 0 to 400 μg/mL and from 0 to 800 μg/mL for 48 h, respectively. Betanin resulted in a 49% inhibition of HepG2 cell proliferation at 200 μg/mL, and betaine yielded a 25% inhibition at 800 μg/mL, implying a higher cytotoxicity of betanin compared with betaine. The results indicated that the contents of health-beneficial compounds in beetroots, betalains and betaine, could be increased by modifying the growing conditions and that betanin and betaine extracted from beetroots had some anticancer effects against HepG2 cells.