The investigation of diferulates in barley (Hordeum vulgare L.) hull extract & bio-assay of hull extract fractions against colon cancer cells.

摘要

Epidemiological studies have shown that diets high in plant fiber and phytoestrogens coincide with lower incidences of gastrointestinal disease and colorectal cancer. Phytoestrogens are plant secondary metabolites which have effects similar to those of mammalian estrogen, but are somewhat weaker in their activity. Diphenolic phytoestrogens, such as lignans, neolignans, and isoflavonoids, are predominantly found in fruits, vegetables, and whole-grain cereals. Once ingested these compounds exhibit activity directly, or are converted to biologically active analogs. Lignans are converted by intestinal microbiota to the weaker mammalian estrogenic analogs, entrerolactone and enterodiol. These weaker estrogenic diphenolic analogs influence a wide range of biological activities (e.g. sex-hormone production, metabolism, intracellular enzymes, malignant cell proliferation, differentiation, cell adhesion and angiogenesis). Hence, these analogs are strong candidates as natural cancer-protective compounds.;Plant fiber is composed mainly of complex carbohydrates (i.e. cellulose and hemicelluloses) and lesser amounts of phenylpropanoids, suberin, cutin, lignin polymers, and lignan oligomers. The cross-linkers of these polymers, oligomers, and polysaccharides are a class of neolignans called dehydrodimers. The focus of the research proposed is the identification of known and possibly novel diferulate dehydrodimers in barley fiber, and assessment of their cytotoxicity to model SW-480 colon cancer cells. In a model study dioxane: methanol extracts of flax (Linum usitatissimum L.), ethyl acetate: methanol extracts of brown rice (Oryza sativa L.), and aqueous methanol extracts of wheat (Triticum aestivum L.) exhibited cytotoxicity against a SW-480 colon cancer cell line. Rice, wheat, and flaxseed extracts exhibiting greatest colon cell cytotoxicity came from those of the whole grain (i.e. grains that are un-milled complete with husk). This result illustrates the importance of identifying the cytotoxic constituents sequestered within the high fiber portions or tissues (i.e. hull/husk, pericarp, aleurone and testa) of grains. For these reasons the whole extract of barley hull and the diferulate dehydrodimer fraction isolated from barley hull extract will be the main focus for the biological assay of plant fiber constituents cytotoxic to colon cancer cells.;A thorough literature search has revealed that some dehydrodimers have been isolated and characterized from barley. Correspondence with those researchers has revealed that no biological assay data for the cytotoxicity of those dehydrodimers towards colon cancer cells exists, and that all possible dehydrodimers have not been isolated and characterized.;This study revealed that the whole base hydrolyzed ethyl acetate extract of barley hull and the isolated diferulate dehydrodimer fraction also exhibited cytotoxicity to SW-480 colon cancer cells. We have also identified the 8-8' open form diferulate and 8-6' decarboxylated diferulate in BHE. Additionally, we have shown that the 8-8' open form diferulate and 8-6' decarboxylated diferulate are also synthesized following the synthesis protocol for the 8-5' benzofuran form diferulate dehydrodimer.