Asian diets include rice as a staple grain, which contributes to almost 90% of world rice consumption. Brown rice, in particular, is known to have several health benefits. As a regular addition to the diet, it can help reduce body weight, lower cholesterol, and suppress inflammation. Brown rice’s ability to neutralize reactive oxygen species and prevent cell damage is vital to many of its health-promoting effects. Although previous studies have shown that the antioxidant compounds in brown rice can protect cells against oxidative stress, knowledge about which main compound contributes to these beneficial properties has long remained a mystery.
In a recent study led by Professor Yoshimasa Nakamura of Okayama University’s Graduate School of Environmental and Life Sciences, researchers in Japan identified cycloartenyl ferulate (CAF) as the main “cytoprotective” or cell-protecting compound in brown rice. CAF is a unique compound due to its hybrid structure. As Professor Nakamura explains, “CAF is a hybrid compound of polyphenol and phytosterol and is expected to be a potent bioactive substance with various pharmacological properties, such as antioxidant effect and blood fat-reducing effect.”
The study, published in the International Journal of Molecular Sciences Volume 24, Issue 1, Jan. 3, 2023, was co-authored by Hongyan Wu of Dalian Polytechnic University and Toshiyuki Nakamura of the Graduate School of Environmental Sciences and of Life of Okayama University. In it, the researchers provide evidence for the antioxidant properties of CAF by showing that it can protect cells from stress caused by hydrogen peroxide. Although hydrogen peroxide is a byproduct of a cell’s metabolic processes, abnormal amounts of the compound can be toxic to cells, causing irreversible damage. Treatment of cells with CAF increased their resistance to toxic stress induced by hydrogen peroxide. Furthermore, CAF provided greater protection against hydrogen peroxide-induced stress compared to alpha-tocopherol and gamma-tocopherol, two other prominent antioxidant compounds previously speculated to be major contributors to the antioxidant capacity of brown rice.
According to study estimates, the amount of CAF in the whole grain of brown rice is five times that of other antioxidant compounds found in brown rice. Additionally, CAF increases the concentration of heme oxygenase-1 or HO-1, an enzyme that facilitates the production of antioxidants. “We show here that CAF significantly increased the mRNA level of HO-1, the small molecular weight antioxidant-producing enzyme, at concentrations similar to those required for cytoprotective effects on resistance to oxidative damage,” explains Professor Nakamura.
The researchers further explored this mechanism of action through experiments in which blocking HO-1 activity by inhibitors significantly reduced the antioxidant effect of CAF. The high abundance and unique mechanism of action are evidence that CAF is the major contributing antioxidant in brown rice.
Through this study, researchers have not only unlocked the secret to brown rice’s health benefits, but have also blocked the component that is primarily responsible for these benefits. This will allow the use of CAF in the development of better novel supplements and food products focused on the health of the consumer. As an optimistic Professor Nakamura observes, “Our study may aid in the development of novel functional foods and supplements based on the functionality of CAFs, such as CAF-based nutraceuticals.“