C: Food Chemistry Phytochemicals and Antioxidant Capacities in Rice Brans of Different Color Byungrok Min, Anna M. McClung, and Ming-Hsuan Chen Abstract: Rice bran, a byproduct of the rice milling process, contains most of the phytochemicals. This study aimed at determining the concentrations of lipophilic, solvent-extractable (free), and cell wall-bound (bound) phytochemicals and their antioxidant capacities from brans of white, light brown, brown, purple, and red colors, and broccoli and blueberry for comparison. The concentrations of lipophilic antioxidants of vitamin E (tocopherol and tocotrienols) and γ -oryzanols were 319.67 to 443.73 and 3861.93 to 5911.12 μg/g bran dry weight (DW), respectively, and were not associated with bran color. The total phenolic, total flavonoid, and antioxidant capacities of ORAC (oxygen radical absorbance capacity), DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging, and iron-chelating in the free fraction were correlated with the intensity of bran color, while variations of these in the bound fraction were less than those in the free fraction among brans. Compounds in the bound fraction had higher antioxidant capacity of ORAC than DPPH, relative to those in the free fraction. The bound fraction of light-color brans contributed as much to its total ORAC as the free fraction. Total proanthocyanidin concentration was the highest in red rice bran, while total anthocyanin was highest in purple brans. The predominant anthocyanin was cyanidin-3-glucoside. Red and purple brans had several fold higher total phenolics and flavonoids as well as ORAC and DPPH, from both free and bound fractions, than freeze-dried blueberry and broccoli. These results indicate that rice brans are natural sources of hydrophilic and lipophilic phytochemicals for use in quality control of various food systems as well as for nutraceutical and functional food application. Keywords: anthocyanins, DPPH radical scavenging capacity, iron-chelating capacity, Oryza sativa L., oxygen radical absorbance capacity (ORAC), pigmented rice, proanthocyanidins, rice Introduction Rice bran is an underutilized byproduct of the rice milling pro- cess that has potential as a rich source of valuable health-promoting compounds. It accounts for approximately 10% of the brown rice by weight and consists of the bran layers (pericarp, testa, nu- cellus, and aleurone layer) and embryo (Orthoefer and Eastman 2004). The health-promoting compounds of bran include phyto- chemicals that are in the lipophilic, hydrophilic, and the cell wall- bound fractions (Adom and Liu 2002; Godber and Juliano 2004; Goffman and Bergman 2004). These phytochemicals are antiox- idants and can account for the health benefits that are associated with the consumption of whole grain, such as the reduced inci- dence of chronic diseases and certain inflammatory diseases (Kris- Etherton and others 2002; Anderson 2003; Venn and Mann 2004; Jocobs and others 2007). The majority of rice varieties grown around the world have light-brown bran. Thus, phytochemical studies have primarily been focused on the bran of light-brown color, and specifically MS 20100777 Submitted 7/9/2010, Accepted 10/7/2010. Author Min is with Food Science and Technology Program, Dept. of Agriculture, Food, and Resource Sciences, Univ. of Maryland Eastern Shore, Princess Anne, MD 21853, U.S.A. Author McClung is with U.S. Dept. of Agriculture, Agricultural Research Service, Dale Bumpers National Rice Research Center, 2890 Hwy 130 E., Stuttgart, AR 72160, U.S.A. Author Chen is with U.S. Dept. of Agriculture, Agricultural Research Service, Rice Research Unit, 1509 Aggie Dr., Beaumont, TX 77713, U.S.A. Direct inquiries to author Chen (E-mail: ming.chen@ars.usda.gov). Mention of trade names or commercial products is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Dept. of Agriculture. on the lipophilic antioxidants, such as vitamin E (refers to any of the 8 naturally occurring forms, α, β , γ , and δ species of both tocotrienols and tocopherols) and γ -oryzanols (ferulic acid es- ter of phytosterols). These lipophilic phytochemicals are potent antioxidants and have shown various health-beneficial effects, in- cluding the prevention of cancer and cardiovascular disease, as well as reduction of oxidative damage in food (Packer 1995; Yasukawa and others 1998; Bramley and others 2000; Cicero and Gaddi 2001; Qureshi and others 2002). The vitamin E in rice bran, as in seeds of most monocots, is composed of a higher percentage of tocotrienols than tocopherols. Studies have demonstrated that tocotrienols have stronger antioxidant capacity than tocopherols and have specific neuroprotective effects, independent of their an- tioxidant activity (Packer 1995). Thus, the rice bran oil should be an attractive source for functional-food applications compared to plant-derived oil from most dicot species (Godber and Juliano 2004). Besides the lipophilic antioxidants, the simple phenols ex- tracted from light brown-colored rice have a potential chemopre- ventative effect (Hudson and others 2000). The cell-wall bound phenolic compounds, which accounts for the majority of the phe- nolic compounds in cereals, can be liberated by digestive enzymes and micro-flora in the colon providing their health-protective ef- fects on site and/or to other body parts after absorption (Adom and Liu 2002; P´ erez-Jim´ enez and Saura-Calixto 2005). Their health benefit has been demonstrated in an animal feeding study in which diet supplemented with the cell wall-bound fraction of rice bran resulted in the reduction of hypertension, hyperlipidemia, and hy- perglycemia (Ardiansyah and others 2006; Jung and others 2007). In addition, pigmented rice specifically from purple- and red- colored bran rice varieties contains abundances of anthocyanins Journal compilation C  2010 Institute of Food Technologists R  No claim to original government works doi: 10.1111/j.1750-3841.2010.01929.x Vol. 76, Nr. 1, 2011  Journal of Food Science C117 Further reproduction without permission is prohibited