http://www.dietcan.net/docs/Polifenoles%20en%20alimentos%20y%20biodisponibilidad.pdf

Polyphenols: food sources and bioavailability

Bioavailability and bioefficacy of polyphenols in humans. I. Review of 97 bioavailability studies

Phenolic acids are aromatic secondary plant metabolites, widely spread throughout the plant kingdom. Existing analytical methods for phenolic acids originated from interest in their biological roles as secondary metabolites and from their roles in food quality and their organoleptic properties. Recent interest in phenolic acids stems from their potential protective role, through ingestion of fruits and vegetables, against oxidative damage diseases (coronary heart disease, stroke, and cancers). High performance liquid chromatography (HPLC) as well as gas chromatography (GC) are the two separation techniques reviewed. Extraction from plant matrixes and cleavage reactions through hydrolysis (acidic, basic, and enzymatic) are discussed as are the derivatization reagents used in sample preparation for GC. Detection systems discussed include UV-Vis spectroscopy, mass spectrometry, electrochemical, and fluorometric detection. The most common tandem techniques are HPLC/UV and GC/MS, yet LC/MS is becoming more common. The masses and MS fragmentation patterns of phenolic acids are discussed and tabulated as are the UV absorption maxima.

Phenolic Acids in Foods: An Overview of Analytical Methodology

Dietary antioxidants, such as water-soluble vitamin C and phenolic compounds, as well as lipid-soluble vitamin E and carotenoids, present in vegetables contribute both to the first and second defense lines against oxidative stress. As a result, they protect cells against oxidative damage, and may therefore prevent chronic diseases, such as cancer, cardiovascular disease, and diabetes. Brassica vegetables, which include different genus of cabbage, broccoli, cauliflower, Brussels sprouts, and kale, are consumed all over the world. This review focuses on the content, composition, and antioxidant capacity both lipid- and water-soluble antioxidants in raw Brassica vegetables. The effects of post-harvest storage, industrial processing, and different cooking methods on stability of bioactive components and antioxidant activity also are discussed.

Natural antioxidants and antioxidant capacity of Brassica vegetables : A review

Absorption and metabolism of polyphenols in the gut and impact on health

Absorption of orally administered chlorogenic acid (5-caffeoylquinic acid) and caffeic acid in rats was studied to obtain plasma pharmacokinetic profiles of their metabolites. Rats were administered 700 micromol/kg body weight of chlorogenic or caffeic acid, and blood was collected from the tail for 6 h after administration. Ingested caffeic acid was absorbed from the alimentary tract and was present in the rat blood circulation in the form of various metabolites. On the other hand, only traces of metabolites, supposedly caffeic and ferulic acids conjugates, were detected in rat plasma for 6 h after chlorogenic acid administration. Chlorogenic acid and small amounts of caffeic acid were found in the small intestine for 6 h after chlorogenic acid administration. These results suggest that chlorogenic acid is not well absorbed from the digestive tract, unlike caffeic acid, and subject to almost no structural changes to the easily absorbed forms.

Absorption of Chlorogenic Acid and Caffeic Acid in Rats after Oral Administration

Six phenolic antioxidative compounds [5-caffeoylquinic acid (chlorogenic acid), 3,5-dicaffeoylquinic acid, quercetin 3-galactoside, quercetin 3-glucoside, quercetin 3-(6-malonylglucoside), and quercetin 3-(6-malonylgalactoside) (tentative)] were identified from the leaves of Corchorus olitorius L. (moroheiya) by NMR and FAB-MS. The contents of these phenolic compounds, ascorbic acid, and α-tocopherol in C. olitorius leaves were determined, and their antioxidative activities were measured using the radical generator-initiated peroxidation of linoleic acid. The results obtained showed that 5-caffeoylquinic acid was a predominant phenolic antioxidant in C. olitorius leaves. Keywords: Corchorus olitorius; antioxidants; phenolics; caffeoylquinic acid; quercetin glycosides

Phenolic antioxidants from the leaves of Corchorus olitorius L.

The antioxidative effects of vegetable extracts were evaluated using linoleic acid emulsion and liposomal phospholipid suspension systems. First, the antioxidative activities of water, ethanol and 2% metaphosphoric acid extracts of the vegetables were investigated by measuring the rate of oxygen consumption in the peroxidation of linoleic acid initiated by a radical generator, 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH), with a Clark electrode in the absence of metal chelators. Ethanol extracts of moroheiya and perilla exhibited the highest antioxidative activities. Without metal chelators, 12 ethanol extracts and one water extract acted as prooxidants, and this phenomenon could be attributed to the prooxidant action of ascorbic acid in the presence of free transition metal ions. Next, peroxyl radical-scavenging activities of vegetable extracts were examined by adding a metal chelator, diethylenetriaminepentaacetic acid (DTPA), to the linoleic acid emulsion system. The results were compared with their antioxidative activities in phospholipid bilayers by measuring the inhibition of lipid peroxidation in large unilamellar vesicles composed of egg yolk phosphatidylcholine (PC). A good correlation was observed between the antioxidative activities obtained from these two systems. The antioxidative activities in the liposomal phospholipid suspension system correlated with total contents of ascorbic acid and polyphenols in vegetable extracts.



© 1999 Society of Chemical Industry

Evaluation of antioxidative activity of vegetable extracts in linoleic acid emulsion and phospholipid bilayers

[6]-Gingerol potently inhibits peroxynitrite-induced oxidation and nitration reactions, but its mechanism of action is unclear. In order to discover the mechanism of inhibition, [6]-gingerol was reacted with peroxynitrite and the reaction mixture was analyzed using HPLC. The HPLC chromatogram showed one novel peak, indicative of the formation of a reaction product between [6]-gingerol and peroxynitrite. This compound was purified and identified as a symmetrical dimer of [6]-gingerol covalently linked at the aromatic ring. It has been assumed that this dimer is generated from a phenoxyl radical intermediate produced from [6]-gingerol via one-electron oxidation by peroxynitrite-derived radicals. We propose a mechanism in which [6]-gingerol scavenges peroxynitrite-derived radicals and consequently inhibits peroxynitrite-induced oxidation and nitration reactions.

Mechanism of inhibition of peroxynitrite-induced oxidation and nitration by [6]-gingerol.

Cucumber plants contain a bitter substance, cucurbitacin C. The compound was isolated from cucumber leaves using preparatory HPLC (high performance liquid chromatography) to investigate the relationship between its content and bitterness of the plant parts. An analytical method for cucurbitacin C using HPLC was also established. A Japanese popular cultivar, 'Sharp 1' contained the compound in the leaves but not in the fruits, while a unique cultivar with white skin 'Shinsyo Hakuhi' contained it both in leaves and fruits. The stem end of 'Shinsyo Hakuhi' fruit contained higher amounts of it than other fruit parts. Cucurbitacin C is a strongly bitter component and its threshold level was less than 0.1 mg/L. The bitter sensation felt when biting the plant parts could be interpreted as corresponding to the content of cucurbitacin C.

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Katsunari Ippoushi

Papers

Absorption of Chlorogenic Acid and Caffeic Acid in Rats after Oral Administration

Phenolic antioxidants from the leaves of Corchorus olitorius L.

Evaluation of antioxidative activity of vegetable extracts in linoleic acid emulsion and phospholipid bilayers

Mechanism of inhibition of peroxynitrite-induced oxidation and nitration by [6]-gingerol.

Cucurbitacin C—Bitter Principle in Cucumber Plants