A joint US-Japanese study has identified the compounds in pre-germinated brown rice responsible for the potential health benefits of this emerging health food.
According to a study published in Journal of Lipid Research, the bioactive components are a related set of sterol-like molecules known as acylated steryl-beta-glucosides (ASGs).
Pre-germinated brown rice is an emerging health food and it is already commercially available in Japan. The rice is soaked in warm water to induce germination, and this stimulates rice enzymes to produce more nutrients.
Preliminary studies with animals reported that a PR-rich diet may improve cognitive function, while other studies reported a potential anti-diabetic effect.
In order to identify the bioactive compounds in the rice, researchers from the Medical College of Georgia, Tokyo Medical and Dental University, and FANCL Research Institute at the FANCL Corporation in Yokohama used by silica gel column chromatography, mass spectrometry (MS) and nuclear magnetic resonance (NMR) techniques.
This enabled the researchers, led by Robert Yu, to identify the bioactives as ASGs, a diverse family of molecules that consists of a glucose derivative, fatty acids, and sterols. The compounds were concentrated in the rice bran (outer layer) and not the seed, so they would not be found in white rice, they reported.
To further explore the role of these compounds, Yu and his co-workers examined the effects of ASGs from pre-germinated brown rice and ASGs from soybean on the activity of two enzymes related to diabetes, homocysteine-thiolactonase (HTase) and Na+/K+ ATPase.
Steryl glucosides (SGs) that were not acylated had no effect of the activity of these enzymes, said the researchers. This result indicated that the chemical structure of the compounds is important, and that activation of the enzymes required the acyl chemical group.
Moreover, the ASGs from soybean did not affect enzyme activity, they added. This suggested that sourcing from the brown rice was important for the anti-diabetic effects.
“Our findings suggest that the molecular species of ASG may play an important contributing role in the anti-diabetic properties of a pre-germinated brown rice diet,” stated the researchers.
“We emphasize that a certain novel ASG is probably involved in PR bran and functions as an enzyme activator,” they concluded.
The study was supported by FANCL, a Japanese supplement company.
Source: Journal of Lipid Research
October 2008, Volume 49, Pages 2188-2196, doi: 10.1194/jlr.M800257-JLR200
"Structural analysis of novel bioactive acylated steryl glucosdies (ASGs) in pre-germinated brown rice bran"
Authors: Seigo Usuki, T. Ariga, S. Dasgupta, T. Kasama, K. Morikawa, S. Nonaka, Y. Okuhara, M. Kise, R.K. Yu