Abstract
Barley is long-identified as a functional food due to its content of micronutrients, β-glucans and vitamins. However, there is scant literature on a number of other nutritionally important biomolecules in the barley grain. This study determined the contents of four biomolecules, each with multiple known human and/or other animal health benefits, in the grains of 27 commercial barley cultivars and 7 landraces of barley from diverse countries of origin. These included the antioxidants, comprised of various vitamin E isomers and polyphenols, the osmoprotectant glycine betaine (GB) that protects cellular cytoplasm from osmotic shock, and the ‘plant stress hormone’ abscisic acid (ABA) which is endogenously expressed in humans and has multiple roles in physiology. All grains exhibited the presence of all biomolecules, suggesting they could potentially make some contribution to the health benefits of barley. The total vitamin E content varied between 19.20 - 54.56 μg/g DW, with α-tocotrienol being the major component (33.9 - 60.7%). The phenolics made up 3.21 - 9.73 mg gallic acid equivalent (GAE)/g DW, exceeding the amounts in the two major cereals, rice and wheat. GB ranged between 0.41-1.40 mg/g DW. The total vitamin E contents and GB typically exceeded those in corn. ABA ranged as 8.50 - 235.46 ng/g dry weight (DW), with the highest inter-variety variability. The data confirm barley to be an excellent source of these nutraceuticals, generally better than other major cereals. Our results thus offer more detailed insights into the potential of barley as a functional food and suggests the need to investigate in depth the health effects of this grain as well as the contribution of genetic and environmental factors.
Highlights
Barley (Hordeum vulgare L.) is a member of the family Poacea
The total phenolic content (TPC) in the cultivars ranged between 3.21 mg gallic acid equivalent (GAE)/g dry weight (DW) (Dhow) and 4.80 mg GAE/g DW (Sloop), while in the landraces, it was higher and ranged between 5.38 (403130, from Kyrgyzstan) to 9.73 mg GAE/g DW (411822, from Turkey)
The range of TPC is in agreement with the Kruma et al, 6 study of various hulled and hull-less barley varieties, wherein the TPC was reported to be in the range of 3.51- 4.60 mg GAE/g DW, and it was suggested that the key determining factor was the variety
Summary
In terms of production and area of harvest, it is the fourth major cereal crop in the world (http://faostat.fao.org). Barley is used either for malting as a precursor in the production of beer or as a feed-stock for animals.[1] over the last decade, there is an increasing interest in barley due to significant amounts of soluble dietary fibre such as β-glucans, arabinoxylans and pectins in its grains.[1,2] The main component of barley grain is starch (70-80%), followed by proteins (10-15%) and non-starch polysaccharides including β-glucans, arabinoxylans and pectins (3-8%)[2]. The polyphenolics, vitamin E isomers and arabinoxylans impart antioxidant properties on barley foods.[1,2] barley foods have ‘nutraceutical’ (nutritional and pharmaceutical) value and are considered ‘functional foods’[7], defined as ‘foods and food components that provide a health benefit beyond basic nutrition’.8
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