Winter, KM 2008, 'Identification of bioactive compounds in wheat', PhD thesis, Southern Cross University, Lismore, NSW.
Copyright KM Winter 2008
Wholegrains have been linked with significant health benefits such as management of cardiovascular disease, diabetes and some cancers. This study aimed to add value to the grain industry by exploring new nutraceutical targets. This was achieved using bioassay guided fractionation. Wheat extracts including wholegrain, endosperm, pericarp and aleurone from different commercial varieties were investigated for in vitro bioactivity in antioxidant, glycosidic enzyme inhibition, anti-inflammatory, anti-cancer, immune function and cholesterol lowering assays. This study found wheat to have antioxidant activity as measured by oxygen radical absorbance capacity (ORAC) assays with higher values reported for the wheat bran extracts. Amino acid trytophan was identified as the most dominant antioxidant compound in the hard wheat variety durum with a TE value of 24217 ± 3158 µmol/g compound. The unsaturated fatty acids oleic, linoleic and linolenic acids proved to be responsible for the majority of the antioxidant activity in the hard wheat bran H2 with TE values of 2424 ± 274, 5220 ± 523 and 5542 ± 102 µmol/g compound, respectively. Wheat bran and germ but not wholegrain or endosperm displayed α-glucosidase and α-amylase inhibiting properties. Through bioassay guided fractionation, phosphoglycerides, 1,2-linoleoylglycero-3-phosphate and 1-palmitoyl-2-linoleoylglycero-3-phosphate were deemed responsible for the α-glucosidase inhibition. Crude wheat extracts were not cytotoxic to a number of human cancerous cell lines. However, some specific fractions showed selective cytotoxicity to the PC3 human prostate tumour cell line. These fractions contained a number of alkylresorcinols with comparative IC50 values (µg/mL) 5-(2-oxotricosanyl)resorcinol (10.9), trans 5-(14-nonadecenyl)resorcinol (13.7), 5-heptadecylresorcinol (22.5) and trans 5-(16-heneicosyl)resorcinol (42.2) to the known anti-cancer agent Chlorambucil (58.7). In this study, wheat bran extracts have not shown any anti-inflammatory inhibition, estrogen binding inhibition, cholesterol lowering or immune function activity. Wheat bran has proved to be a highly nutritious by-product of the wheat milling industry with a number of protective health effects.