(P26-005-25) Human Metabolism of Sorghum bicolor Extracts in Colon Cancer Cells

Objectives: Epidemiological studies support the consumption of whole grains as part of a balanced diet, partly because it may prevent the development of colorectal cancer. Some Sorghum bicolor varietals contain high levels of phytochemicals known to protect plants from oxidative damage. The bioavailability of these phytochemicals and their metabolites ultimately influences their chemopreventive potential. Using colorectal cancer cells grown in transwells as an in vitro model of human digestion, we will identify metabolites generated after treatment with sorghum extracts and investigate potential changes in the expression of genes involved in antioxidant pathways.

Methods: Two ethanol-based extracts of S. bicolor used in this study were supplied by the USDA and are derived from a brown sorghum varietal containing high levels of polyphenols. Red Leaf Biologics™ provided us with their proprietary powdered red leaf sorghum supplement that we dissolved in cell culture media for our studies (25mg/mL). Cytotoxicity of these three extracts was determined in Caco-2 cells using the MTT assay. For the metabolite analysis, Caco-2 cells were seeded in a transwell insert with a permeable membrane. After ~21 days, these cells typically form a tight monolayer. Cells were exposed to 1.25μl/ml of S. bicolor extracts or Redaxin™ for 24h. Medium was collected and frozen for HPLC analysis. Cells were harvested, RNA was isolated, and cDNA synthesized. mRNA expression of antioxidant genes was assessed with gene-specific primers using qPCR.

Results: Extracts from SC Leaf and Redaxin™ showed limited cytotoxicity up to 20 μl/ml. However, sorghum bran extract was cytotoxic at concentrations > 1.25µl/ml. Furthermore, Redaxin™ upregulated mRNA expression of glutathione peroxidase 1 and 2 (31.25 µg/mL final concentration). Treatment with SC leaf or bran extracts (1.25<µl/ml) did not result in any significant changes in gene expression.

Conclusions: Gene expression studies suggest that Redaxin™ may increase the expression of key antioxidant enzymes, potentially explaining a mechanism by which Redaxin™ may act as an antioxidant and chemopreventative.

Funding Sources: USDA-ARS and Towson University