Chemopreventive properties of dietary rice bran: current status and future prospects

Abstract

Emerging evidence suggests that dietary rice bran may exert beneficial effects against several types of cancer, such as breast, lung, liver, and colorectal cancer. The chemopreventive potential has been related to the bioactive phytochemicals present in the bran portion of the rice such as ferulic acid, tricin, β-sitosterol, γ-oryzanol, tocotrienols/tocopherols, and phytic acid. Studies have shown that the anticancer effects of the rice bran-derived bioactive components are mediated through their ability to induce apoptosis, inhibit cell proliferation, and alter cell cycle progression in malignant cells. Rice bran bioactive components protect against tissue damage through the scavenging of free radicals and the blocking of chronic inflammatory responses. Rice bran phytochemicals have also been shown to activate anticancer immune responses as well as affecting the colonic tumor microenvironment in favor of enhanced colorectal cancer chemoprevention. This is accomplished through the modulation of gut microflora communities and the regulation of carcinogen-metabolizing enzymes. In addition, the low cost of rice production and the accessibility of rice bran make it an appealing candidate for global dietary chemoprevention. Therefore, the establishment of dietary rice bran as a practical food-derived chemopreventive agent has the potential to have a significant impact on cancer prevention for the global population.

Figure 1.

A breakdown of the components found in dietary rice bran. Green boxes represent components with literature-supported cancer chemopreventive activity.

Figure 2.

Diagram depicting chemopreventive mechanisms of action associated with dietary rice bran and brown rice bioactive components. COX-2, cyclooxygenase-2; DC, dendritic cells; IDO, indoleamine 2,3-dioxygenase; iNOS, inducible nitric oxide synthase; NF-κB, nuclear factor-κB; NK, natural killer; NO, nitric oxide; PGE₂, prostaglandin E₂.

Figure 3.

Visual examples of bran polished from distinct rice varieties that contain unique pigments and bioactive components with cancer chemopreventive potential.