Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2000
Publication Date: N/A
Interpretive Summary: Rice bran is a low-value by-product from milling rice kernels. If it is stabilized by a heat treatment, it can be a source of food-grade oil. Previously, it was shown that rice-bran oil was a source of antioxidants, chemicals which can prevent disease by removing free radicals. We have further examined the antioxidant chemicals in rice bran. We found that through a further heating process, two new compounds were obtained. These compounds are members of a group called tocotrienols. These novel tocotrienols were shown to lower cholesterol in chickens, inhibit the proliferation of cancer cells, and had potent antioxidant characteristics. In all these effects, the novel tocotrienols were superior to the previously known ones. This research could lead to a new process that will enhance the value of rice bran oil and benefit consumers by providing a health promoting vegetable oil.
Technical Abstract: Two novel tocotrienols were isolated from stabilized and heated rice bran, apart from the known alpha-, beta-, gamma-, and delta-tocopherols and tocotrienols. These new tocotrienols were separated by HPLC, using a normal phase silica column. Their structures were determined by ultraviolet, infrared, nuclear magnetic resonance, circular dichroism and high resolution mass spectroscopy's and established as desmethyl tocotrienol [3,4-dihydro-2-methyl-2-(4,8,12-trimethyltrideca-3'(E),7'(E),- 11'-trienyl)-2H-1-benzopyran-6-ol] and didesmethy tocotrienol [3,4- dihydro-2-(4,8,12-trimethyltrideca-3'(E),7'(E),11'-trienyl)-2H-1- benzopyran-6-ol]. These tocotrienols significantly lowered serum total- and LDL-cholesterol levels and inhibited HMG-CoA reductase activity in chickens. They had much greater in vitro antioxidant activities and greater suppression of B16 melanoma cell proliferation than a-tocopherol and known tocotrienols. Results indicated that the number and position of methyl substituents in tocotrienols affect their hypocholesterolemic, antioxidant and antitumor properties.