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The aim of this study was to assess the bioactive compounds of apple and pear peel and pulp in vitro and their influence on plasma lipids and antioxidant potentials in vivo. The antioxidant potentials measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH), beta-carotene bleaching (beta-carotene), and nitric oxide inhibition radical scavenging (NO) tests in apple peel and pulp were significantly higher than in pear peel and pulp, respectively. The ethanol extract of apple peels showed the strongest inhibition of lipid peroxidation as a function of its concentration and was comparable to the antioxidant activity of butylated hydroxyanisole. The pear pulp extract had the weakest antioxidant ability, whereas other extracts such as apple pulp and pear peel were nearly equal. The antioxidant activities comprised contributions from polyphenols, phenolic acids, and flavonoids and correlated well with polyphenols and flavonoids. The correlation coefficients between polyphenols and antioxidant activities by DPPH, beta-carotene, and NO were as follows: 0.9207, 0.9350, and 0.9453. Contrarily, the correlation coefficient between the content of dietary fiber and the antioxidant activities test was low. The content of all studied indices in apple and pear peel was significantly higher than in peeled fruits (p < 0.05). Diets supplemented with fruit peels exercised a significantly higher positive influence on plasma lipid levels and on plasma antioxidant capacity of rats than diets with fruit pulps.

Maize, wheat, amaranth, rice and soybean were screened for protein content. Alcoholsoluble (A1 and A2) and glutelin (G1 and G2) fractions were isolated and compared in terms of their amino acid and protein compositions. The average proportions of nitrogen content between total alcohol-soluble proteins (TASP) and total glutelins (TGlu) in the pseudocereals amaranth and soybean were about 1.8:26.9 and 14.9:12.3 respectively. In the cereals maize and wheat these proportions were 47.8:33.2 and 44.7:31.2 respectively. The sum of essential amino acids was 47.6 and 60.3 g per 100 g protein in amaranth and soybean respectively. The highest contents of methionine, lysine and arginine were found in the pseudocereals. The relatively high content of essential amino acids shows that pseudocereals could be used as a nutrient substitute for cereals.

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