Other Health Promoting Compounds

Avenanthramides


Avenanthramides are low-molecular weight, soluble phenolic compounds which are unique to only oat grain. An avenanthramide molecule is a conjugate of phenylpropanoid acid with anhtranilic or 5-hydroxy anthranilic acid. In oats there are more than 20 distinct forms of avenanthramides differing in the substituents of the acid rings, but the three major forms are A, B and C.


Avenanthramides are antipathogens (phytoalexins) and they play a role in the oat grain's defense against attack by the fungal pathogens. They are produced in oat grain in response to pathogen exposure but also cultivation and environmental conditions affect avenanthramide concentration. The concentration in oat grains vary between 2 mg/kg - 53 mg/kg.


Avenanthramides have been shown to exhibit potent antioxidant properties both in vitro and in vivo studies. In human and animal tests avenanthramides have demonstrated anti-inflammatory, antiproliferative, vasodilation, anti-itch and cytoprotection effects. Thus, in addition to β-glucan's well-established cholesterol-lowering properties, oats' avenanthramides are also believed to contribute to the reduction of CHD in oat-rich diet.


Tocols


Tocols (tocopherols and tocotrienols) are natural antioxidants in grains that may benefit human and animal health. They exist as lipid-soluble compounds and are unevenly distributed within the grain (α-tocotrienol primarily in the endosperm, whereas α-tocopherol in the germ). Tocols are known as vitamin E. Their biological activity results from their ability to donate phenolic hydrogen atoms to free radicals, thus breaking destructive chain reactions. Other beneficial therapeutic properties of tocols include the ability to reduce serum cholesterol concentration and to inhibit the growth of certain cancer cells.

 

The tocotrienols are stronger free radical scavengers than tocopherols. α-tocotrienol is the major homologue of the tocols in oats, followed by α-tocopherol. Various other homologues are found in minor or trace amounts. A survey of 12 genotypes grown in three locations in the USA found a range of 9 - 19 mg/kg for the concentration of α-tocotrienol, and 7 - 10 mg/kg for α-tocopherol. Mannerstedt-Fogelfors et al. (2004) examined the effect of N fertiliser on the concentrations of avenanthramides and tocols. The cultivar x N-level interaction was significant for content of α-tocopherol, α-tocotrienol and total tocols.


Compounds occurring in trace amounts


Phenolic compounds, flavonoids, saponins, lignans and sterols are found in oat grain, but in minor quantities. Their concentrations are very low compared to tocols. These compounds have antioxidant and other bioactivities.The most common phenolic compounds in whole grain oat are ferulic acid, diferulic acids, sinapic acid and avenanthramides (274, 121, 60, and 30 µg/g of dry weight, respectively).

 

 

Meydani, M. (2009). Potential health benefits of avenanthramides of oats. Nutrition Reviews 67, pp. 731-735.

 

Peterson, D.M., Dimberg, L.H. (2008). Avenanthramide concentrations and hydroxycinnamoyl-CoA: hydroxyanthranilate N-hydroxycinnamoyltransferase activities in developing oats. J Cereal Sci 47, pp. 101-108.

 

Peterson, D.M., Jensen, C.M., Hoffman, D.L., Mannerstedt-Fogelforsl, B. (2007). Oat tocols: saponification vs. direct extraction and analysis in high-oil genotypes. Cereal Chem 84, pp. 56-60.


Skoglund, M., Peterson, D.M., Andersson, R., Nilsson, J., Dimberg, L.H. (2007). Avenanthramide content and related enzyme activities in oats as affected by steeping and germination. J Cereal Sci, in Press.

 

Mannerstedt-Fogelfors, B., Sohl, J., Alström, S., Peterson, D.M. (2004). Antioxidant and β-glucan content in oats as affected by soil type and N-level. In: Proceedings of the 7th International Oat Conference. Helsinki, Finland. Peltonen-Sainio, P., Topi-Hulmi, M. (eds.) Jokioinen: MTT Agrifood Research Finland, Agrifood Research Reports 51, p. 220.

 

Pihlava, J.-M., Eurola, M., Hietaniemi, V., Kontturi, M., Vuorinen, M. (2004). Factors affecting the concentration of avenanthramides in oats. In: Proceedings of the 7th International Oat Conference. Helsinki, Finland. Peltonen-Sainio, P., Topi-Hulmi, M. (eds.) Jokioinen: MTT Agrifood Research Finland, Agrifood Research Reports 51, p. 119.

 

Peterson, D.M. (2004). Oat - a multifunctional grain. In: Proceedings of the 7th International Oat Conference. Helsinki, Finland. Peltonen-Sainio, P., Topi-Hulmi, M. (eds.) Jokioinen: MTT Agrifood Research Finland, Agrifood Research Reports 51, pp. 21-25.

 

Bryngelsson, S., Mannerstedt-Fogelfors, B., Kamal-Eldin, A., Andersson, R., Dimberg, L.H. (2002) Lipids and antioxidants in groats and hulls of Swedish oats (Avena sativa L). J Sci Food Agric 82, pp. 606-614.

 

Peterson, D. M., Hahn. M.J., Emmons, C.L. (2002). Oat avenanthramides exhibit antioxidant activities in vitro. Food Chem 79, pp. 473-478.

 

Peterson, D. M. (2001). Oat antioxidants. J Cereal Sci 33, pp. 115-129.

 

Kamal-Eldin, A., Appelqvist, L.-Å. (1996) The chemistry and antioxidant properties of tocopherols and tocotrienols. Lipids 31, pp. 671-701.

 

Peterson, D. M., Qureshi, A. (1993). Genotype and environmental effects on tocols of barley and oats. Cereal Chem 70, pp. 157-162.