Oat Bioactives: Types, Mechanisms, and Functions
J. B. BLUMBERG (1). (1) Tufts University, Boston, MA, U.S.A.
In addition to their content of fiber, minerals, and vitamins, the phytochemical profile of oats (<i>Avena sativa</i> L.) contribute importantly to the health benefits associated with consumption of this whole grain, including support of digestive and cardiovascular health. The principal bioactives in oats include avenanthramides (AVA), carotenoids, flavonoids, lignans, phytosterols, and tocotrienols. Unique to oats, AVA are a group of 20 soluble alkaloids as hydroxycinnamic acids conjugated to anthranilic acid. The potent antioxidant capacity of AVA was likely the basis for the early use of oat flour as an anti-rancidity ingredient in other foods. The AVA content of oat varies from 74-142 mg/kg depending on cultivar and processing. In vitro experiments have shown that AVA inhibits IL-1ß-stimulated vascular endothelial cell adhesion molecules (ICAM-1, VCAM-1, E-selectin) and proinflammatory cytokines/chemokines (IL-6, IL-8, MCP-1). These actions appear to be mediated via attenuation of IkB kinase phosphorylation to suppress redox-sensitive signal transduction by NFkB. The anti-inflammatory and anti-itch properties of oats have been known for many years with oatmeal as a remedy for poison ivy, sunburn, eczema, and psoriasis. In a randomized clinical trial of 16 older women, 9.2 mg AVA daily for 8 wk was found to reduce inflammation (CRP, IL-1ß, NFkB) and increase antioxidant defenses (SOD) induced by a downhill walking exercise. Another clinical trial found 3.12 mg AVA daily for 4 wk in 120 healthy adults increased serum SOD and glutathione, reduced lipid peroxidation, and improved lipid profiles. The unique presence and characterized bioavailability of AVA in oats suggests its status may serve as a biomarker of oat consumption. Further research on the bioavailability and metabolism of AVA and their role in health promotion and disease prevention is ongoing.
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