Health-promoting antioxidants from pigmented rice
2009
Romero, M.V. | Panajon, N.M. | Manaoes, R.V. | Mamucod, H.F., Philippine Rice Research Inst., Maligaya, Science City of Muñoz, 3119 Nueva Ecija (Philippines). Rice Chemistry and Food Science Div.
Chronic diseases such as cancer, cardiovascular disease, and diabetes account for almost half of deaths in the Philippines. Reactive cell-damaging free radicals are implicated in these diseases. This is a major reason for the heightened interest in antioxidants which are commonly found in foods. Pigmented rice such as black, purple, or red rice is a good source of antioxidants because it contains anthocyanins which are effective free radical scavengers with anti-inflamatory and anti-cancer activities. In this study, the anthocyanin content and antioxidant activity of some popular pigmented rice varieties in the Philippines were determined using abdel-aal and 2,2-diphenyl-1-picrylhydrazyl (DPPH) methods, respectively. For comparison, non-pigmented rice varieties (IR64 and IMS2) were also evaluated. The results showed significantly higher amount of anthocyanin for Tapul (3445 mg/kg) and Ballatino (3358 mg/kg) than NSIC Rc19 (12 mg/kg) and almost nothing for IR64 and IMS2. The drastic reduction of anthocyanin content upon polishing clearly indicated its significant presence in the bran. To elucidate the relative amount of anthocyanin in the different parts of the grain Ballatino was separated into hull, bran, and endosperm and each portion was analyzed for anthocyanin content using high-performance liquid chromatography. Rice hull, bran, and endosperm had 129, 4605 and 86 mg/kg of anthocyanin, respectively. It is obvious that anthocyanin was concentrated in the bran. The antioxidant activity assay revealed that the pigmented varieties, Tapul and NSIC Rc19, exhibited significantly higher activity against the free-radical DPPH than IR64. Therefore, local pigmented rice varieties can serve as excellent source of antioxidants which are effective in preventing the harmful effects of oxidative stress. Moreover, maximum health-promoting benefits can be harnessed if pigmented rice is consumed in its unpolished form. This study is a step towards addressing the major challenge of impending the high incidence of chronic diseases in our country.
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