Crude aqueous and ethanolic extracts of root tissue of red (Rd) and high-pigment (HP) beet (Beta vulgaris L.) strains exhibited antioxidant and phase II enzyme-inducing activities, and these extracts were fractionated using Sephadex LH-20 chromatography. These bioactivities tended to become co-enriched in early and late eluting fractions, comprising 5-25% of the material recovered from the column. Liquid chromatography-mass spectrometry (MS) was used to resolve and identify multiple betalain components in the most potent quinone reductase (QR)-inducing fractions. Active fractions were found to contain vulgaxanthins I and II, and (iso)betanin, but other components remained unidentified. Two of the isolated active fractions were incorporated into rodent diets at 10-150 ppm over a 2-mo period to assess bioavailability and in vivo efficacy for phase II enzyme induction in various organs. No statistically significant effect of diet was obtained, and wide ranges of tissue enzyme levels among individual animals were observed. This lack of effect and diversity in response to diet may be related to the wide range in absorptive capacity of and/or insufficient level or enrichment of the active agents or to difficulties in assessing such activity in vivo. Subsequent to the animal studies, betanin was isolated in pure form, identified by MS analysis, and confirmed to be QR inducers in the bioassay.
Bibliographical noteFunding Information:
This work was supported by the College of Agricultural and Life Sciences and School of Education of the University of Wisconsin–Madison and by a grant from the Robert Draper Technology Innovation Fund from the Wisconsin Alumni Research Foundation. We acknowledge the contributions of University of Wisconsin–Madison units of Department of Horticulture for their generous supply of beetroots and the Analytical Instrumentation Center of the School of Pharmacy for support in obtaining mass spectrometric data. The authors are also grateful for the assistance provided by Mr. Hang Xiao and Ms. Lei Liu during the conduct of the animal studies. C.-H. Lee and M. Wettasinghe contributed equally to this work. M. Wettasinghe is currently affiliated with the Alberta Research Council, Edmonton, Alberta, Canada, T6N 1E4. Address correspondence to K. L. Parkin, Department of Food Science, University of Wisconsin, 1605 Linden Drive, Babcock Hall, Madison, Wisconsin 53706. Phone: 608–263–2011. FAX: 608–262–6872. E-mail: email@example.com.