Biopotency of vitamin E in barley

Abstract

I . Investigations were carried out to establish the total biopotency of the natural vitamin E isomers in barley compared with that of DL-a-tocopheryl acetate.2. The chick was used as an experimental animal. Prevention of nutritional encephalomalacia (NE) and chick liver-storage and plasma-storage assays of vitamin E were the methods used in the study. The individual tocopherols and tocotrienols, both in the tissue samples and in the grain and barley oil, were analysed using high-pressure liquid chromatography (HPLC) with fluorescence detection. The diagnosis of NE was based on careful clinical and histopathological observations.3. It can be concluded from the results that full protection against NE in the chicks was obtained with a supplementation level of 7.5 mg DL-a-tocopheryl acetate/kg diet (i.e. a total vitamin E content of 11.20 mg/kg diet) or with a supplement of 8.7 g barley oil/kg diet (i.e. a total vitamin E content of 22.99 mg from barley oil/kg diet). This gave a biopotency factor of 0.49 for barley for prevention of NE of the chicks, as compared to that of DL-a-tocopheryl acetate.4. Using regression analysis a statistically linear relationship could be observed between the total dietary vitamin E level and the response, as measured by the total vitamin E content in the liver and plasma, both in the groups supplemented with DL-a-tocopheryl acetate and in the groups supplemented with corresponding amounts of vitamin E in barley oil. The liver and plasma responses to the total vitamin E in the barley-oil diet compared with those of the DL-a-tocopheryl acetate reference diet gave identical values for the regression coefficients, i.e. in both liver-storage and plasma-storage assays the value for slopes of dose-response lines was 0.37. This means that the biopotency of the total vitamin E in barley was 37% of that of dietary DL-a-tocopheryl acetate. Thus, barley is not as rich a source of vitamin E as could be supposed on the basis of the chemical determination of its total vitamin E content.5. It was possible to verify this experimentally established biopotency of 0.37 for the total vitamin E in barley by converting the chemically determined amounts of the vitamin E isomers in barley into DL-a-tocopheryl acetate equivalents by multiplying them with internationally accepted potency factors for the individual natural isomers (DL-a-tocopheryl acetate 1.00, D-a-tocopherol 1.49, D-8-tocopherol 0.60, D-y-tocopherol 0.1 5, D-a-tOCOtrienOl 0.37).6. In spite of the high proportion of a-and p-tocotrienols in the barley-oil diets (about 60% of the total vitamin E content), only traces of these isomers could be detected in the plasma and none could be detected in the liver. On the other hand, calculation of the individual hiopotencies for the different isomers in the barley-oil diet by comparing the dose responses, diet: liver, separately for each isomer with those of DL-a-tocopheryl acetate, resulted in biopotency values for a-and 8-tocopherol which were twice as high as the internationally accepted conversion fac...

Monitoring of vitamin E status of dry, early and mid-late lactating organic dairy cows fed conserved roughages during the indoor period and factors influencing forage vitamin E levels

“…Cereals, e.g. barley and oats, were reported to be vital sources of vitamin E for domestic animals (Hakkarainen et al., 1984). However, in this study vitamin E content of dry cereals was low.…”

“…This could be explained by the fact that only α‐tocopherols were determined, as the scope of this monitoring study was limited to a general screening, whereas cereal grains such as barley, oats, wheat and rye are suggested to contain significant amounts of natural non‐α‐tocopherols, e.g. α‐tocotrienol (Hakkarainen et al., 1984). Although this (partially) might explain the difference between our vitamin E results of grains and values reported in literature, grains will not be a major vitamin E supplier in the monitored farms due to their limited proportions in the diet.…”

Morphological Studies on Nutritional Encephalomalacia in Chicks, with Special Reference to Mineralized Deposits in the Cerebellum

“…In earlier experimental work we have used the prevention of N E under standardized conditions as a means for evaluating the biological activity of vitamin E and its isomers in experimental diets ( HAKKARAINEN et al, 1983;HAKKARAINEN et al, 1984). The finding of calcified or mineralized deposits, besides the histopathognomonic alterations, in the cerebelli of not only encephalomalacic but also clinically healthy chicks was the ultimate reason for the present study.…”

Physicochemical and pharmacological characterization of α-tocopherol-loaded nano-emulsion system

“…Vitamin E is an essential nutrient derived from various crops, such as barley, wheat, and soybean (Hakkarainen et al, 1984;Hall and Laidman, 1968;Ito et al, 2007). Vitamin E has several isomers, including ␣-, ␤-, ␥-, and ␦-tocopherols (Leth and Sondergaard, 1977), the activity and bioavailability of which vary depending on their structures and physicochemical properties.…”