Narasimhan Ramarathnam

THE CONTRIBUTION OF PLANT FOOD ANTIOXIDANTS TO HUMAN HEALTH

Abstract We have been actively involved in the isolation and characterization of endogenous plant antioxidants that are believed to inhibit lipid peroxidation and offer protection against oxidative damage to membrane functions. Antioxidants have been isolated from conventional food sources, such as tea (green and black), sesame and wild rice, and also from other plant sources, such as rice hulls, and crude plant drugs. Data on new types of water-soluble and lipid-soluble plant antioxidants are provided, and the biological activity and functionality of these antioxidants are discussed.

Studies on changes in fatty acid composition and content of endogenous antioxidants during γ irradiation of rice seeds

Accelerated aging effects, induced by y irradiation, were investigated on the fatty acid composition of lipids and on the content of endogenous antioxidants of four Indica and four Japonica rice seeds with and without intact hull. While the linoleic acid content of the phospholipids decreased gradually with the increase in irradiation doses, there was a corresponding increase in the linoleic acid content of the free fatty acids. Such changes were drastic, especially in the case of Japonica rice seeds irradiated without intact hull. However, the neutral lipids were found to be resistant to γ irradiation.The α-tocopherol content was found to decrease (markedly) in rice seeds irradiated with or without hull, especially in the Japonica rice seeds. At a dose of 15 kGy only traces of a-tocopherol could be detected in Japonica and Indica rice seeds irradiated with and without intact hull. Oryzanol, a relatively weaker anti-oxidant, was found to be more resistant to oxidative damage than a-tocopherol. At 15 kGy, the oryzanol content ranged from 59 μg to 170 μg/g lipid in rice seeds irradiated with intact hull, while the corresponding value for rice seeds irradiated without hull was 52 μg to 153 μg/g lipid.The overall susceptibility to oxidative damage was less in Indica rice seeds, indicating that the antioxidative defense system offered better protection in overcoming oxidative stress in Indica rice hull than in Japonica rice hull.

Determination of HEL (Hexanoyl-Lysine Adduct): A Novel Biomarker for Omega-6 PUFA Oxidation

Published evidences indicate that reactive oxygen species (ROS) can induce lipid peroxidation, which plays important role in the pathophysiology of numerous diseases including atherosclerosis, diabetes, cancer and aging process. Monitoring of oxidative modification or oxidative damages of biomolecules may therefore be essential for the understanding of aging, and age-related diseases. N-epsilon-Hexanoyl-lysine (HEL) is a novel lipid peroxidation biomarker which is derived from the oxidation of omega-6 unsaturated fatty acid. In this chapter, development of HEL ELISA and its applications are reported. Assay range of HEL ELISA was 2-700 nmol/L, and showed good linearity and reproducibility. Accuracy of this assay was validated by recovery test and absorption test. HEL concentration in human urine was 22.9 ± 15.4 nmol/L and it was suggested that HEL exists as low molecular substances, in a free or in the peptide-attached form. In contrast with the urine sample, serum HEL was suggested to exist in the protein-attached form, and hydrolysis by protease might be essential for the accurate measurement of HEL in protein containing samples such as serum and cultured cells. By sample pretreatment with proteases, HEL was successfully detected in oxidized LDL, oxidized serum, and rat serum. In conclusion, HEL ELISA can be applied to measure urine, serum, and other biological samples independent of the animal species, and may be useful for the assessment of omega-6 PUFA oxidation in the living bodies.

Superoxide Radical Scavenging Activities of Wines, and Antioxidative Properties of Fractions Recovered from Merlot Wine Pomace

Wine samples (n = 43) differing in origin, grape variety, and vintage were analyzed for total phenolic content, sulfur dioxide content, color (OD520), and superoxide radical scavenging activities (SOSA). A direct correlation between the wine color (r = 0.7517), its phenolic content (r = 0.9686), and the ability of the wine constituents to scavenge superoxide radicals was established using a simple regression analysis. Distribution of the SOSA in wines was further examined by fractionating 12 wines into three fractions with a C18 Sep-pak cartridge. The correlation coefficient between SOSA and total phenol content in the fractions was r = 0.2705 in fraction A (containing phenolic acids, sugars, organic acids, amino acids, and salts) r = 0.9575 in fraction B (containing procyanidins, flavonols, and catechin) and r = 0.9785 in fraction C (containing anthocyanins and tannins), respectively. As the phenolic content of fraction C was about twofold higher than that of fraction B, fraction C contributed most to the SOSA value in wine. Phenolic compounds were extracted with 50% ethanol from Merlot wine pomace. The extract showed high antioxidant activities, and also scavenged the superoxide and hy-droxyl radicals quite efficiently.

Antioxidative Defense System and Free Radical Scavenging Potentials of Cereals

Cereals occupy an important place in the human diet. In addition to being the primary source of carbohydrates, cereals also provide us with vitamins, trace minerals, and dietary fibers. With the recent increase in interest in the intake of dietary antioxidants, cereals have also been investigated for their antioxidant defense potentials. This review focuses on the description of a phenolic antioxidant defense system in the rice hull that has been demonstrated to offer chemical protection to the rice grain from undergoing oxidative damage. In addition, data are presented to demonstrate the free radical scavenging potentials of the hot aqueous extracts of some of the selected cereal grains. Information is also provided on the newly identified antioxidants in wild rice, and in the green leaves of young barley plants.