Document Type

Thesis

Publication details

Liu, L 2009, 'Phytochemical and pharmacological perspectives of wheat grain and lupin seed', PhD thesis, Southern Cross University, Lismore, NSW.

Copyright L Liu 2009

Abstract

Wheat and lupin are important crops grown in Australia with massive production every year. Traditionally, both wheat and lupin have been consumed as human foods for their health benefits, which may be due in part to the biologically active phytochemicals they contain. This thesis describes the phytochemical and pharmacological investigations of wheat bran, different wheat bran layers, wheat germ, lupin seed and germinating lupin seed. Three biological activities were investigated including antioxidant, glycaemic index lowering and anticancer activities. The antioxidant activity was assessed using the Oxygen Radical Absorbance Capacity (ORAC) assay, the glycaemic index lowering activity was determined using an α-glucosidase inhibitory assay and the anticancer activity was investigated through cytotoxicity of several cancer cell lines.

Wheat bran was identified to have ORAC, α-glucosidase inhibitory and cytotoxic activities. The investigation of ORAC activity of wheat bran was extended to different wheat bran layers. L-tryptophan was isolated and identified as a potent antioxidant in wheat bran with an ORAC value of 8424 μmol TE/g. Unsaturated free fatty acids including linolenic (5542 μmol TE/g), linoleic (5520 μmol TE/g) and oleic (2424 μmol TE/g) acids were identified as major ORAC contributors of wheat bran. The investigation of cytotoxicity of wheat bran against PC3 human prostate cancer cell line identified four cytotoxic resorcinols including 5-heptadecylresorcinol (IC50 = 64.7 μM), 5-(14-nonadecenyl) resorcinol (trans) (IC50 = 36.6 μM), 5-(16-heneicosenyl) resorcinol (trans) (IC50 = 105.0 μM) and 5-(2-oxotricosanyl) resorcinol (IC50 = 24.4 μM). The investigation of α-glucosidase inhibitory activity was extended to wheat germ. Two compounds, 1,2-dilinoleoylglycero-3-phosphate (IC50 = 38.9 μM) and 1-palmitoyl-2-linoleoyl-glycero-3-phosphate (IC50 = 47.9 μM), were isolated and identified to have α-glucosidase inhibitory activity.

The investigation of cytotoxicity was further extended to Australian grown narrow leaf lupins. Two lupin alkaloids, angustifoline and lupanine, were isolated. It was found that not only the lupin extracts but also the alkaloids had only mild cytotoxicity (average IC50 > 500 μg/mL). Two isoflavonoids, genistin and 6"-malonylgenistin, were identified and quantified in germinating narrow leaf lupin seeds. The levels of these two compounds increased more than 50-fold after 5 days germination. The genistin level of the lupin seed after 48~120 hours germination (0.055 ~ 0.627 mg/g) increased to the same level found in soybean and soybean products (0.072 ~ 0.968 mg/g).

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