Identification and Quantitation of Flavanols and Proanthocyanidins in Foods: How Good are the Datas?

Evidence suggesting that dietary polyphenols, flavanols, and proanthocyanidins in particular offer significant cardiovascular health benefits is rapidly increasing. Accordingly, reliable and accurate methods are needed to provide qualitative and quantitative food composition data necessary for high quality epidemiological and clinical research. Measurements for flavonoids and proanthocyanidins have employed a range of analytical techniques, with various colorimetric assays still being popular for estimating total polyphenolic content in foods and other biological samples despite advances made with more sophisticated analyses. More crudely, estimations of polyphenol content as well as antioxidant activity are also reported with values relating to radical scavenging activity. High-performance liquid chromatography (HPLC) is the method of choice for quantitative analysis of individual polyphenols such as flavanols and proanthocyanidins. Qualitative information regarding proanthocyanidin structure has been determined by chemical methods such as thiolysis and by HPLC-mass spectrometry (MS) techniques at present. The lack of appropriate standards is the single most important factor that limits the aforementioned analyses. However, with ever expanding research in the arena of flavanols, proanthocyanidins, and health and the importance of their future inclusion in food composition databases, the need for standards becomes more critical. At present, sufficiently well-characterized standard material is available for selective flavanols and proanthocyanidins, and construction of at least a limited food composition database is feasible

An industry consensus study on an HPLC fluorescence method for the determination of (±)-catechin and (±)-epicatechin in cocoa and chocolate products

<p>Abstract</p> <p>Background</p> <p>This manuscript describes the results of an HPLC study for the determination of the flavan-3-ol monomers, (±)-catechin and (±)-epicatechin, in cocoa and plain dark and milk chocolate products. The study was performed under the auspices of the National Confectioners Association (NCA) and involved the analysis of a series of samples by laboratories of five member companies using a common method.</p> <p>Methodology</p> <p>The method reported in this paper uses reversed phase HPLC with fluorescence detection to analyze (±)-epicatechin and (±)-catechin extracted with an acidic solvent from defatted cocoa and chocolate. In addition to a variety of cocoa and chocolate products, the sample set included a blind duplicate used to assess method reproducibility. All data were subjected to statistical analysis with outliers eliminated from the data set.</p> <p>Results</p> <p>The percent coefficient of variation (%CV) of the sample set ranged from approximately 7 to 15%.</p> <p>Conclusions</p> <p>Further experimental details are described in the body of the manuscript and the results indicate the method is suitable for the determination of (±)-catechin and (±)-epicatechin in cocoa and chocolate products and represents the first collaborative study of this HPLC method for these compounds in these matrices.</p

Antioxidant Activities of Fractions of Polymeric Procyanidins from Stem Bark of Acacia confusa

The polymeric procyanidins extracted from Acacia confusa stem bark were fractionated with a step gradient of water, methanol and acetone on a Sephadex LH-20 column. The antioxidant activity of the collected fractions was investigated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging and ferric reducing/antioxidant power (FRAP) assays. All fractions possessed potent antioxidant activity with the highest activity observed for fraction F9. The matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and reversed-phase high performance liquid chromatography (RP-HPLC) analyses suggested that the collected fractions consisted primarily of oligomeric and polymeric procyanidins, with different polymer ranges and most abundant polymer size. For each fraction, catechin and epicatechin were present as both terminal and extension units, and epicatechin was the major component in the extended chain. The mean degree of polymerization (mDP) of each fraction differed, ranging from 1.68 (fraction F2) to 17.31 (fraction F11). There was a relationship between antioxidant activity (IC50/DPPH and FRAP) and mDP (R2DPPH = 0.861, P = 0.006 and R2FRAP = 0.608, P = 0.038), respectively. However, the highest antioxidant activity of fraction (F9) was not coincident with the maximum mDP of fraction (F11)

Introduction of apple ANR genes into tobacco inhibits expression of both CHI and DFR genes in flowers, leading to loss of anthocyanin

Three genes encoding anthocyanidin reductase (ANR) in apple (Malus×domestica Borkh.), designated MdANR1, MdANR2a, and MdANR2b, have been cloned and characterized. MdANR1 shows 91% identity in coding DNA sequences with MdANR2a and MdANR2b, while MdANR2a and MdANR2b are allelic and share 99% nucleotide sequence identity in the coding region. MdANR1 and MdANR2 genes are located on linkage groups 10 and 5, respectively. Expression levels of both MdANR1 and MdANR2 genes are generally higher in yellow-skinned cv. Golden Delicious than in red-skinned cv. Red Delicious. Transcript accumulation of MdANR1 and MdANR2 genes in fruits gradually decreased throughout fruit development. Ectopic expression of apple MdANR genes in tobacco positively and negatively regulates the biosynthesis of proanthocyanidins (PAs) and anthocyanin, respectively, resulting in white, pale pink-coloured, and white/red variegated flowers. The accumulation of anthocyanin is significantly reduced in all tobacco transgenic flowers, while catechin and epicatechin contents in transgenic flowers are significantly higher than those in flowers of wild-type plants. The inhibition of anthocyanin synthesis in tobacco transgenic flowers overexpressing MdANR genes is probably attributed to down-regulation of CHALCONE ISOMERASE (CHI) and DIHYDROFLAVONOL-4-REDUCTASE (DFR) genes involved in the anthocyanin pathway. Interestingly, several transgenic lines show no detectable transcripts of the gene encoding leucoanthocyanidin reductase (LAR) in flowers, but accumulate higher levels of catechin in flowers of transgenic plants than those of wild-type plants. This finding suggests that the ANR gene may be capable of generating catechin via an alternative route, although this mechanism is yet to be further elucidated

Apple phytochemicals and their health benefits

Evidence suggests that a diet high in fruits and vegetables may decrease the risk of chronic diseases, such as cardiovascular disease and cancer, and phytochemicals including phenolics, flavonoids and carotenoids from fruits and vegetables may play a key role in reducing chronic disease risk. Apples are a widely consumed, rich source of phytochemicals, and epidemiological studies have linked the consumption of apples with reduced risk of some cancers, cardiovascular disease, asthma, and diabetes. In the laboratory, apples have been found to have very strong antioxidant activity, inhibit cancer cell proliferation, decrease lipid oxidation, and lower cholesterol. Apples contain a variety of phytochemicals, including quercetin, catechin, phloridzin and chlorogenic acid, all of which are strong antioxidants. The phytochemical composition of apples varies greatly between different varieties of apples, and there are also small changes in phytochemicals during the maturation and ripening of the fruit. Storage has little to no effect on apple phytochemicals, but processing can greatly affect apple phytochemicals. While extensive research exists, a literature review of the health benefits of apples and their phytochemicals has not been compiled to summarize this work. The purpose of this paper is to review the most recent literature regarding the health benefits of apples and their phytochemicals, phytochemical bioavailability and antioxidant behavior, and the effects of variety, ripening, storage and processing on apple phytochemicals

Effect of Polyphenols on Oxidative Stress and Mitochondrial Dysfunction in Neuronal Death and Brain Edema in Cerebral Ischemia

Polyphenols are natural substances with variable phenolic structures and are elevated in vegetables, fruits, grains, bark, roots, tea, and wine. There are over 8000 polyphenolic structures identified in plants, but edible plants contain only several hundred polyphenolic structures. In addition to their well-known antioxidant effects, select polyphenols also have insulin-potentiating, anti-inflammatory, anti-carcinogenic, anti-viral, anti-ulcer, and anti-apoptotic properties. One important consequence of ischemia is neuronal death and oxidative stress plays a key role in neuronal viability. In addition, neuronal death may be initiated by the activation of mitochondria-associated cell death pathways. Another consequence of ischemia that is possibly mediated by oxidative stress and mitochondrial dysfunction is glial swelling, a component of cytotoxic brain edema. The purpose of this article is to review the current literature on the contribution of oxidative stress and mitochondrial dysfunction to neuronal death, cell swelling, and brain edema in ischemia. A review of currently known mechanisms underlying neuronal death and edema/cell swelling will be undertaken and the potential of dietary polyphenols to reduce such neural damage will be critically reviewed

Design and test of a dynamic balancing machine for small rotors.

http://www.archive.org/details/designtestofdyna00hammU.S. Navy (U.S.N.) author