Avenanthramide

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Avenanthramides are a type of oat phytoalexins that exist predominantly in the groats of oat seeds.[1]

Among a group of at least 25 avenanthramides[2] that differ in the substituents on the cinnamic acid and anthranilic acid rings, three are predominant in oat grain: Bc (also called avenanthramide C), Bf (also called avenanthramide B) and Bp (also called avenanthramide A).

In vitro experiments indicate they have significant antioxidant activities, with Bc > Bf > Bp.[3] In human and animal tests, this antioxidant capacity provides health benefits ranging from reduced rate of LDL oxidation[4] to protecting against cancers and heart disease.[5] Because of its antioxidant properties, high levels of avenanthramide are desirable in oat grain. Researchers at the Agricultural Research Service (ARS) currently are trying to understand what environmental factors regulate the amount of avenanthramide produced in oat grain. [1] Past studies have found an increase in avenanthramide production in plants that are infected by a fungus, leading researchers to believe that avenanthramide is used as a chemical defense in helping the oat grain fight off the fungus. ARS researchers found that cultivars with the strongest resistance to crown rust, a fungus that affects oat grains, had the highest concentration of avenanthramide. However, because not all cultivars with high crown rust resistance had high levels of avenanthramide, researchers suspect other environmental factors play a role in avenanthramide production. Nevertheless, scientists suggest farmers can still select for highly resistant cultivars to increase the production of avenanthramide in their grain.[6]

They are tranilast analogues and have anti-inflammatory and antifibrotic properties, probably due to TGF-beta inhibitory effects.

Anti-inflammatory and anti-itch properties[edit]

Ancient literature describes the anti-inflammatory and antipruritic properties of oatmeal. In 1978 the U.S. Food and Drug Administration (FDA) external review panel noted that colloidal oatmeal was safe and effective for the symptomatic relief of dry skin and itching.

Recent studies were conducted to verify whether avenanthramides are also responsible for the antipruritic activity of oat extracts. The results of human in vivo skin prick tests combined with an in vitro model, investigating the inhibitory activity of avenanthramides on the histamine net release from rat peritoneal mast cells stimulated by substance P showed a clear indication that avenanthramides found in oat extract play a major role in the reduction of itching and redness in skin. Because of the fundamental role of histamine in itch sensation, these results can be considered as a clear indication that oat extracts with a standardized content of avenanthramides are useful materials to reduce histamine related itch sensation and redness in skin.[7]

Most recently, extracts containing avenanthramides have been used in veterinary medicine in various topical forms, such as shampoos, sprays and ear cleansing solutions for the relief of adverse skin conditions, including atopic dermatitis.

Notes[edit]

  1. ^ Emmons, C. L. & Peterson, D. M. (1999) Antioxidant activity and phenolic contents of oat groats and hulls. Cereal Chem. 76:902-906.
  2. ^ 2. Collins, F. W. (1989) Oat phenolics: avenanthramides, novel substituted N-cinnamoylanthranilate alkaloids from oat groats and hulls. J. Agric. Food Chem. 37:60-66.
  3. ^ Peterson D.M.1; Hahn M.J.; Emmons C.L.(2002) Oat Avenanthramides Exhibit Antioxidant Activities In Vitro. Food Chem. 79:4:473-478
  4. ^ Chen, C.Y & Blumberg , J. B. (2004) Vitamin C to Enhance Hamster and Human LDL Resistance to Oxidation J. Nutr. 134:1459-1466
  5. ^ Bailey, G.S. & Williams, D.E.(1993) Potential Mechanisms for Food-Related Carcinogens and Anticarcinogens. Food Technol. 47:105-118
  6. ^ "Studies Provide Insight into Key Oat Chemical". USDA Agricultural Research Service. February 1, 2010. 
  7. ^ J. Vollhardt, D.A. Fielder and M. Redmond (2000) Identification and Cosmetic Application of Powerful Anti-irritant Constituents of Oat Grain; Proceedings of the 21st IFSCC International Congress. 395