Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2013
Publication Date: 4/17/2013
Publication URL: http://handle.nal.usda.gov/10113/58001
Citation: Forster, G., Raina, K., Kumar, A., Kumar, S., Agarwal, R., Chen, M., Bauer, J., McClung, A.M., Ryan, E. 2013. Rice varietal differences in bioactive bran components for inhibition of colorectal cancer cell growth. Food Chemistry. 141(2):1545-1552. Interpretive Summary: Most people consume white milled rice where the bran layer of the grain has been removed as part of the milling process. Over 70 million tons of rice bran is produced annually and most of this is used as low value animal feed. However the bran layer is known to contain various compounds like fatty acids, Vitamin E, and phenolics that have been shown to have health beneficial properties. This study was conducted to determine if different rice cultivars vary in the chemical components of the bran and if these components impact growth of human colon cancer cells. Seven rice varieties were evaluated that had brown, purple or red bran. The bran was removed and characterized for lipid, total phenolics, and lipid-soluble antioxidants including vitamin E sub-components. The varieties were found to differ in bran chemical composition. Extracts from the bran were used to test proliferation of three lines of human colon cancer cells in a laboratory study. The two red, one purple, and one of the brown bran cultivars had the most significant inhibitory activity on the cancer cells with the inhibition being positively correlated with the amount of bran in the cell culture media. The concentration of total phenolic compounds was found to be most highly correlated with reduction in cancer cell growth. These results demonstrate that the chemical composition of bran differs among rice varieties and that some of these compounds show promise in reducing human colon cancer cell growth.
Technical Abstract: Studies support that the bran fraction of rice contains bioactive compounds capable of inhibiting the formation of colonic tumors. Screening bran extracts from diverse rice varieties represents a novel approach to assessing the colon cancer chemopreventive properties of rice bran. We analyzed a panel of rice varieties for differences in their total percent lipid contents and found a range from 5-16 percent. Next, we analyzed concentration profiles of fatty acids, vitamin E isoforms (alpha, gamma, and delta - tocotrienols and tocopherols), gamma oryzanol, and total phenolics. The panel of rice bran extracts displayed a variety dependent 0-70 percent range in growth inhibition of human colorectal cancer (CRC) cells across the Caco-2, HT-29, and SW-480 cell lines. Spearman correlation analysis was performed to identify the significance of bioactive compounds for CRC cell growth inhibitory activity. Total phenolics and gamma tocotrienol were positively correlated with reduced CRC cell growth across all varieties examined (p<0.05). Significant variation in the ratios and stoichiometry of rice bran components and their differential effects on CRC viability suggests that not all rice brans exhibit dietary CRC chemoprevention activity. Specific rice varieties possessing these bioactive compounds are traits to encourage for agricultural production and for dietary prevention of CRC formation in humans.