BIOCHEMICAL STUDIES ON SOME ANTIOXIDANT COMPOUNDS IN WHEAT AND BUCKWHEAT

Abstract

This experiment was designed to investigate the effect of different types of bread, wheat bran extract and buckwheat hull extract on lipid profile and oxidative stress of normal and hypercholesterolemic rats. Buckwheat grains had high contents of protein, fat, crude fiber and ash compared to that found in wheat grains. The predominate fatty acid in buckwheat was linoleic acid 38.81% while palmitic acid was the major fatty acid found in wheat. The predominate amino acid in buckwheat glutamic acid 14.951 g/100g protein. Also, glutamic acid was the major amino acid (24.827 g/100g protein) in wheat followed by proline (9.165 g/100g protein). Balady bread which prepared by substitute 20% from wheat flour by buckwheat whole meal flour was acceptable. Buckwheat bread (100% buckwheat flour) contain the highest amount of protein 15.33% and crude fiber 8.20% while high fiber bread recorded the highest amount of fat 3.80% and ash 2.35% compared to other types of bread. Buckwheat hull contained the highest amounts from total phenol, total flavonoid and tannins (1250.06, 1168.09 and 85.05 mg/100g sample, respectively). It is also clear that, buckwheat bread (100% buckwheat flour contain the highest amounts from total phenol, total flavonoid and tannins compared to other types of bread. Ferulic acid was predominate (80.45%) in wheat bran but protocatechuic acid was the highest phenolic acid (66.31%) found in buckwheat hull. Regarding to flavonoids derivatives, rutin was the major flavonoid found in buckwheat hull (1255.7μg/g). On the other hand, apigenin was found to be the only flavonoid detected in wheat bran. The highest antioxidant activity effect was recorded by buckwheat hull followed by buckwheat grains compared with other samples. Between all types of bread (buckwheat bread 100% buckwheat flour, balady bread 20% buckwheat flour, high fiber bread and balady bread 100% wheat flour) and buckwheat hull extract and wheat bran extract buckwheat bread 100% buckwheat flour showed the highest reduction in the values of plasma total cholesterol (TC), triglyceride (TG), low density lipoprotein (LDL-C), aspartate aminotransferase (AST), alanine aminotransferase (ALT), glucose, urea and creatinine and significant increase in high density lipoprotein (HDL-C) in rats fed on hypercholesterolemic diet supplemented with buckwheat bread 100% buckwheat flour compared to hypercholesterolemic control. Regarding to oxidative stress rats fed on hypercholesterolemic diet supplemented with buckwheat bread 100% buckwheat flour showed the highest decrease in plasma malondialdehyde (MDA) level and the highest increase in total antioxidant capacity (TAC) and activities of glutathione reductase (GR) and glutathione-S-transferase (GST) compared with other hypercholesterolemic treated groups. Therfore buckwheat bread (100% buckwheat flour) and balady bread supplemented with 20% buckwheat whole flour have the ability to protecting experimental animals fed hypercholesterolemic diet of oxidative stress and hypercholesterolemia. Key words: wheat, buckwheat, chemical composition, antioxidant compounds, hypercholesterolemia