Phenolics and polyphenolics in foods, beverages and spices: Antioxidant activity and health effects – A review

Phenolics in Food and Nutraceuticals is the first single-source compendium of essential information concerning food phenolics. This unique book reports the classification and nomenclature of phenolics, their occurrence in food and nutraceuticals, chemistry and applications, and nutritional and health effects. In addition, it describes antioxidant activity of phenolics in food and nutraceuticals as well as methods for analysis and quantification. Each chapter concludes with an extensive bibliography for further reading. Food scientists, nutritionists, chemists, biochemists, and health professionals will find this book valuable.

Phenolics in food and nutraceuticals

The effect of modified atmosphere packaging (MAP) and cooking on the flavonoids and vitamin C content (ascorbic + dehydroascorbic acid; AA + DHAA) of fresh-cut spinach was evaluated. The total flavonoid content (approximately 1000 mg kg(-)(1) f.w.) remained quite constant during storage in both air and MAP atmospheres, while vitamin C (750 mg kg(-)(1)f.w.) was better preserved in MAP-stored spinach. AA was transformed to DHAA during storage, and its concentration was higher in MAP-stored tissues. The free-radical scavenging activity of the isolated flavonoids was tested, and only those flavonoids with either a dihydroxyl grouping or acylated with ferulic acid showed significant activity. A decrease in the total antioxidant activity was observed during storage, particularly important in MAP-stored spinach. The higher content of DHAA and lower content of both AA and antioxidant flavonoids in the MAP-stored samples could explain this antioxidant activity decrease. Boiling extracted 50% of total flavonoids and 60% vitamin C in the cooking water. However, flavonoid glucuronides were extracted more in the cooking water than the other glycosides. The vitamin C content of the cooked tissue was higher in those samples stored in MAP.

Effect of postharvest storage and processing on the antioxidant constituents (flavonoids and vitamin C) of fresh-cut spinach.

Publisher Summary This chapter discusses the important reactions of the hydroxyl group. Knowledge of the relative reactivities of hydroxyl groups in carbohydrates is fundamental to a thorough understanding of carbohydrate chemistry. The chapter explains esterification, which forms the largest part of the literature since 1953 on selective reactions of carbohydrates. The common methods of esterification utilize an acid chloride or an acid anhydride as the reagent, but other acid derivatives often show different selectivities. An investigation pertinent to the subject of favored reactivity concerned the reactions of certain acyl halides with ethanol, in acetone or chloroform solution. The mixed-order nature of some of these reactions suggested that every rate-determining transition-state contained the substrate, the nucleophile (ethanol), and an acceptor— X—for hydrogen bonding, suitable acceptors being an acetone molecule, a chloride ion, or another ethanol molecule. The possibility that intramolecular hydrogen-bonding does not persist in pyridine and that the advantage of a bonded hydroxyl group would be lost, invalidates the explanation of favored reactivity. But if the hydrogen-bonding to pyridine is hindered in the transition state, intramolecular hydrogen-bonding could conceivably assume importance.

Relative Reactivities of Hydroxyl Groups in Carbohydrates

In this study a method was designed to assess non-destructively the type of UV-screening compounds present in the leaf epidermis. The method is based on the recording and calculation of the ratio of UV-excitation spectra of chlorophyll fluorescence (FER) from the adaxial and abaxial sides of bifacial leaves, or from older and younger segments of monocotyledonous leaves. The logarithm of this ratio (logFER) matched the absorption spectrum of the UV-absorbers present in the leaf, as confirmed by its overlap with the absorption spectrum of the methanolic extract of the leaf or of the isolated epidermis. By using the logFER approach, it was possible to demonstrate that the concentration but not the classes of compounds present in the epidermis that are responsible for UV-screening is affected by the side and the age of the leaves. In contrast, measurements from the leaves of seven dicots and one monocot indicated large difference in the classes of these compounds between species. Finally, it was shown that the logFER in the UV is independent of the emission wavelength, and that the method can be used for quantitative measurements. This method expands to the spectral domain the use of ChlF for the estimation of the leaf epidermal transmittance.

http://max2.ese.u-psud.fr/publications/CerovicZG2002PCE.pdf

The use of chlorophyll fluorescence excitation spectra for the non‐destructive in situ assessment of UV‐absorbing compounds in leaves

Flavonol glycosides in leaves of Spinacia oleracea

Three highly oxygenated flavone glucuronides in leaves of Spinacia oleracea

Cyanogenic glycosides in leaves of Perilla frutescens var. acuta

A new xanthone C-glucoside, position isomer of mangiferin, from Anemarrhena asphodeloides Bunge.

On treatment of some C-and O-D-glucopyranosides with diazomethane in methanol or in methanol-dimethylformamide mixture, a partial methylation of the sugar moiety took place, though to a slight extent, to give a mixture of methyl ethers, in which 3-methyl ether is the major. The reaction is much favored in the presence of a small amount of stannous chloride. A O-α-D-glucopyranoside gave almost exclusively the corresponding 3-methyl ether of the glucose residue, while the β-anomer provided, beside 3-methyl ether, 2, 3-dimethyl ether nearly in equal amount. The benzylidene derivatives of O-α-and β-D-glucosides gave also the corresponding 3-methyl ether but 2, 3-dimethyl ether was formed only in trace and, instead, 2-methyl ether was provided.

Masakazu Aritomi

Papers

Flavonol glycosides in leaves of Spinacia oleracea

Three highly oxygenated flavone glucuronides in leaves of Spinacia oleracea

Cyanogenic glycosides in leaves of Perilla frutescens var. acuta

A new xanthone C-glucoside, position isomer of mangiferin, from Anemarrhena asphodeloides Bunge.

Partial Methylation with Diazomethane of the Sugar Moiety of Some C- and O-D-Glucopyranosides