Table 2.
Phytochemicals present in barley and oats, methods used for extracting them and their reported bioactivities.
| Phytochemical | Source | Extraction Solvent/Technique Used | Bioactivity | Commercial Availability |
|---|---|---|---|---|
| β-glucan | Barley | 4% 1 M NaOH [27]; Water at 55 °C and pH 7.0 [32]; Pressurized hot water extraction at 155 °C, 18 min and 50 bar [91] | Lowers cholesterol [92] reducing the chances of coronary and ischemic heart disease. Lowers glycaemic index and postprandial glucose levels [93]. | Barley β-glucan is available as Glucagel®, PromOat®, Glucan 300® |
| Oat | Ethanol reflux followed by extraction with a sodium carbonate solution at pH 10 [26]. | |||
| Phenolic acids (PA) | Barley | Free phenolics—Acetone/water (4/1) [51,94]; ethanol/water (4/1) [51]; pressurized liquid extraction [61]. Bound phenolics—20 h prolonged alkaline hydrolysis [51]; Acid hydrolysis [53]; Sequential acid, α amylase and cellulose hydrolysis [55] | PA act as antioxidants and protect against the destructive activity of free radicals. They reduce the risk of chronic age-related diseases such as cardiovascular diseases, diabetes and ageing, by reducing oxidative stress [95]. PA bound to dietary fiber may prevent cancer of the colon [96]. | Green tea extracts rich in phenolic acids are available as Bulk Powders® and Super Green Tea Diet® |
| Oat | Free phenolics—Methanol [97], Methanol/water (4/1) [52]; Acetone/water (1/1) [95]; 80% ethanol [46,57]; Bound phenolics—Alkaline hydrolysis [52], acid hydrolysis [52,53] | |||
| Avenanthramides (AV) | Oat | 80% methanol [56,98]; 80% ethanol [57,58]. | AV are bioavailable and act as antioxidants by inhibiting LDL oxidation in synergy with Vitamin C [99]. They demonstrate anti-allergic activities. | |
| Flavonoid | Barley | 40% ethanol [100] | Proanthocyanidins have ferrous chelating activity and influence the bioavailability of iron in the body [101]. Tricin shows chemopreventive effects against breast and colon cancer cells [102]. | Citrus flavonoids are available as Citrus Bioflavonoid Caps® and a similar product from soy is available as Phytosoya®, SoyChoice® |
| Oat | Free flavonoids—80% ethanol [103]; Bound flavonoids—Digestion using NaOH, followed by acidification, removal of lipids using hexane and further extraction using ethyl acetate [103]. | |||
| Tocols | Barley | Extraction with methanol, followed by drying and extraction using hexane [79]; Saponification using KOH, ethanol, NaCl and pyrogallol at 70 °C for 25 min. This is followed by cooling on ice bath and extraction using hexane:ethyl acetate (9:1) [76,77]. | Tocols are generically known as Vitamin E and exhibit antioxidant activity. Tocotrienols demonstrate reduction in serum total cholesterol and LDL cholesterol levels in vivo [104]. | |
| Oat | Extraction techniques used are same as those for barley [76,79,81]. | |||
| Proteins | Barley | Alkaline extraction using NaOH and addition of HCl at pH 4.6 for precipitation of protein [105]; A peptide lunasin has been isolated from barley with phosphate-buffered saline supplemented with protease inhibitor cocktail, followed by column and immunoaffinity chromatography [89]. | Hydrolyzed peptides from barley proteins have demonstrated anti-oxidant, antihypertensive and anti-diabetic effects in vitro [105]. The peptide lunasin is a cancer preventive agent and is bioavailable [89]. Hydrolysates from oat proteins demonstrate ACE-I enzyme inhibitory activity in vitro [88]. | Milk derived peptides is available as Calpis® and a sardine fish derived peptide product is available as Valtyron®, (Source—Fish) Valtyron® |
| Oat | Alkaline extraction followed by isoelectric precipitation [88]. |