Different cultivars of four Vaccinium species [Vaccinium corymbosum L (Highbush), Vaccinium ashei Reade (Rabbiteye), Vaccinium angustifolium (Lowbush), and Vaccinium myrtillus L (Bilberry)] were analyzed for total phenolics, total anthocyanins, and antioxidant capacity (oxygen radical absorbance capacity, ORAC). The total antioxidant capacity of different berries studied ranged from a low of 13.9 to 45.9 μmol Trolox equivalents (TE)/g of fresh berry (63.2−282.3 μmol TE/g of dry matter) in different species and cultivars of Vaccinium. Brightwell and Tifblue cultivars of rabbiteye blueberries were harvested at 2 times, 49 days apart. Increased maturity at harvest increased the ORAC, the anthocyanin, and the total phenolic content. The growing location (Oregon vs Michigan vs New Jersey) did not affect ORAC, anthocyanin or total phenolic content of the cv. Jersey of highbush blueberries. A linear relationship existed between ORAC and anthocyanin (rxy = 0.77) or total phenolic (rxy = 0.92) content. In general,...

Antioxidant capacity as influenced by total phenolic and anthocyanin content, maturity, and variety of Vaccinium species

Humans are unable to synthesise L-ascorbic acid (L-AA, ascorbate, vitamin C), and are thus entirely dependent upon dietary sources to meet needs. In both plant and animal metabolism, the biological functions of L-ascorbic acid are centred around the antioxidant properties of this molecule. Considerable evidence has been accruing in the last two decades of the importance of L-AA in protecting not only the plant from oxidative stress, but also mammals from various chronic diseases that have their origins in oxidative stress. Evidence suggests that the plasma levels of L-AA in large sections of the population are sub-optimal for the health protective effects of this vitamin. Until quite recently, little focus has been given to improving the L-AA content of plant foods, either in terms of the amounts present in commercial crop varieties, or in minimising losses prior to ingestion. Further, while L-AA biosynthesis in animals was elucidated in the 1960s, 1 it is only very recently that a distinct biosynthetic route for plants has been proposed. 2 The characterisation of this new pathway will undoubtedly provide the necessary focus and impetus to enable fundamental questions on plant L-AA metabolism to be resolved. This review focuses on the role of L-AA in metabolism and the latest studies regarding its bio- synthesis, tissue compartmentalisation, turnover and catabolism. These inter-relationships are considered in relation to the potential to improve the L-AA content of crops. Methodology for the reliable analysis of L-AA in plant foods is briefly reviewed. The concentrations found in common food sources and the effects of processing, or storage prior to consumption are discussed. Finally the factors that determine the bioavailability of L-AA and how it may be improved are considered, as well as the most important future research needs. # 2000 Society of Chemical Industry

Plant L‐ascorbic acid: chemistry, function, metabolism, bioavailability and effects of processing

Three assays were compared for the determination of total antioxidant capacity in human serum: the oxygen radical absorbance capacity (ORAC) assay, the Randox Trolox-equivalent antioxidant capacity (Randox-TEAC) assay, and the ferric reducing ability (FRAP) assay. There was a weak but significant linear correlation between serum ORAC and serum FRAP. There was no correlation either between serum ORAC and serum TEAC or between serum FRAP and serum TEAC. The effect of dilution on the serum TEAC value and the use of inhibition percentage at a fixed time, without considering the length of inhibition time in the quantitation of results, adversely affected the Randox-TEAC assay. The FRAP assay is simple and inexpensive but does not measure the SH-group-containing antioxidants. The ORAC assay has high specificity and responds to numerous antioxidants. By utilizing different extraction techniques in the ORAC assay, one can remove serum proteins and also make some gross differentiation between aqueous and lipid-soluble antioxidants. However, the ORAC assay requires ∼60 min more than the FRAP or Randox-TEAC assay to quantitate results.

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Comparison of different analytical methods for assessing total antioxidant capacity of human serum

A comparative evaluation of thiobarbituric acid methods for the determination of malondialdehyde in biological materials

gamma-tocopherol, the major form of vitamin E in the US diet, deserves more attention.

A highly sensitive high-performance liquid chromatography method for the estimation of ascorbic and dehydroascorbic acid in tissues, biological fluids, and foods.

The metabolism of alpha- and gamma-tocopherol was studied in three groups of rats that were fed a modified AIN-76 diet containing normal (NE, 0.2 g alpha-tocopherol/kg), high (HE, 1.0 g alpha-tocopherol/kg) or low (LE, less than 0.02 alpha-tocopherol/kg) vitamin E for 3 mo. After 1, 2 and 3 d of an oral dose of 20 mg of alpha-tocopherol, gamma-tocopherol or both, the levels of the two vitamers were measured in plasma and tissues and in some cases in isolated microsomal and mitochondrial fractions from liver. Twenty-four hours after an oral dose of 20 mg gamma-tocopherol the levels of alpha-tocopherol in plasma and tissues remained constant and higher levels of gamma-tocopherol were found in tissues in which low alpha-tocopherol levels could be found such as in the LE group. In spite of this, it was enabled to remain there, after 2 and 3 d gamma-tocopherol had decreased levels in all tissues. When given in combination with alpha-tocopherol, the levels of gamma-tocopherol were lower than when gamma-tocopherol was given alone. Microsomes and mitochondria from livers of LE group bound five and nine times more alpha-tocopherol than gamma-tocopherol in rats dosed with equal amount of alpha- or gamma-tocopherol, respectively. These data indicate that the mechanisms that regulate the metabolism of vitamin E are highly specific for alpha-tocopherol. Moreover, the relative amount of alpha-tocopherol determined the levels of gamma-tocopherol in tissues. However, the retention of gamma-tocopherol in tissues did not depend on the presence of alpha-tocopherol.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of Absorption, Transport and Tissue Uptake of RRR-α-Tocopherol and d-γ-Tocopherol in the White Rat

A method for the analysis of malonaldehyde by ion pairing high-performance liquid chromatography is described. The method is direct; no thiobarbiturate chromogen formation is required, and sample preparation is simple. After deproteinization with 50% ethanol and removal of particulate by centrifugation samples were passed through a small silica amino column to remove contaminants. Diluted samples (20 μL) were injected onto an octadecylsilane column (25 cm×4.6 mm ID, 5 μm) which is eluted with 30 mM sodium phosphate buffer, pH 6.5 containing 30% ethanol and 1 mM tetradecyltrimethylammonium bromide. Detection was accomplished by monitoring absorbance at 267 nm. The lower limit for reliable quantification was 5 pmol per injection. The method has been successfully applied to the quantification of malonaldehyde present in plasma, urine and tissues of rats kept under different dietary conditions as well as afterin vivo treatment with CCl4 and iron-dextran. The method was also applied to the quantification of malonaldehyde during liver microsomal lipid peroxidation and was compared to the thiobarbituric acid test.

René Madère

Papers

A highly sensitive high-performance liquid chromatography method for the estimation of ascorbic and dehydroascorbic acid in tissues, biological fluids, and foods.

Mechanisms of Absorption, Transport and Tissue Uptake of RRR-α-Tocopherol and d-γ-Tocopherol in the White Rat

Malonaldehyde determination in tissues and biological fluids by ion-pairing high-performance liquid chromatography

Transport of α-and γ-tocopherol in human plasma lipoproteins

Interrelationship and competition of α- and λ-tocopherol at the level of intestinal absorption, plasma transport and liver uptake