Phenol Consumption Research Articles

Influence of MoS2 catalyst morphology on the hydrodeoxygenation of phenols

The hydrodeoxygenation (HDO) activity of several unsupported MoS2 catalysts, each with different morphology, has been determined using the reactants phenol, 4-methylphenol and 4-methoxyphenol. Exfoliated MoS2 catalyst was compared to crystalline MoS2, MoS2 prepared by in situ decomposition of ammonium heptamolybdate (AHM) and MoS2 prepared by in situ decomposition of molybdenum naphthenate (MoNaph). Exfoliated MoS2 had the highest first-order rate constant per Mo edge site for the consumption of phenol and 4-methylphenol. Hydrogenolysis of the C–OH bond of 4-methylphenol was favored over MoS2 with a lower degree of stacking (MoS2 derived from AHM) whereas aromatic ring hydrogenation of phenol was favored over MoS2 with a higher degree of stacking (exfoliated MoS2).

Radiolysis of phenol in aqueous solution at elevated temperatures

γ-Radiolysis and pulse radiolysis of phenol in aqueous solution up to supercritical condition have been carried out. G-values of phenol consumption and product formation have been determined. While dihydroxybenzenes were major products at room temperature, multi-ring compounds and benzene were formed above 300 °C. This indicates reaction mechanism was changed above 300 °C, where phenoxyl radical plays a predominant role. This is supported by the observation of phenoxyl radical in pulse radiolysis. In supercritical water, the G-values increased with decrease of density.

Purple grape juice inhibits 7,12-dimethylbenz[a]anthracene (DMBA)-induced rat mammary tumorigenesis and in vivo DMBA-DNA adduct formation

There has been considerable interest in identifying specific foods and phytochemicals that may have breast cancer preventive properties. Concord grapes are rich in polyphenolic chemicals and anthocyanin pigments that may have biological properties which could suppress cancer such as having antioxidant, antiproliferative, and proapoptotic actions. To determine the potential breast cancer protective action of purple grape juice, we examined the effect of grape juice consumption on the initiation stage of 7,12-dimethylbenz[a]anthracene (DMBA)-induced rat mammary tumorigenesis and on the in vivo formation of rat mammary DNA adducts in female Sprague–Dawley rats. Consumption of grape juice significantly inhibited mammary tumor mass at termination and the growth of tumors for the first 5 weeks of detectable tumor development. Consumption of grape juice phenolics by rats also significantly inhibited in vivo mammary DMBA-DNA adduct formation by 34 and 56% for animals fed phenolics at 346 and 692 mg/dL, respectively, compared to controls. Mammary 8-oxo-deoxyguanosine (8-oxo-dG) levels decreased by 25 and 37%, respectively, but the differences were not statistically significant. Liver DMBA-DNA adducts decreased by 10–30%, while 8-oxo-dG adducts remained unchanged, following grape juice intake. Liver glutathione S-transferase activity was significantly increased following grape juice consumption, but only at the highest level of intake. In addition, liver activities of catalase increased and xanthine oxidase decreased significantly, but only at the highest grape juice dose. Thus, these studies indicate that specific constituents or combinations of phytochemicals in purple grape juice can block the initiation stage of DMBA-induced rat mammary tumorigenesis. This tumor inhibitory effect was associated with a suppression of mammary DMBA-DNA adduct formation, which in part may be explained by increased liver activity of the phase II metabolizing enzyme, glutathione S-transferase. Mammary and liver 8-oxo-dG levels were not significantly altered by grape juice consumption. Thus, grape juice constituents appear to have benefit in decreasing susceptibility of the rat mammary gland to the tumor-initiating action of DMBA.

The biodegradation of phenol at high initial concentration by the yeast Candida tropicalis

Strain Candida tropicalis was isolated from acclimated activated sludge, and was identified as a member of the genus Candida. Phenol biodegradation using a pure culture of C. tropicalis was studied. The results showed that C. tropicalis has pretty high phenol degradation potential, which could thoroughly degrade the phenol of 2000 mg l −1 in the mineral salt medium within 66 h. High inoculum volume lessened phenol toxic property for the cells and increased phenol biodegradation velocity. However, for a certain starting inoculum, with the step increase of phenol concentration, substrate inhibition was obviously enhanced, and more phenol consumption was not assimilated by cell for growth, but was used to counteract strong substrate inhibition. In addition, the cell growth and phenol degradation intrinsic kinetics of C. tropicalis in batch cultures were also investigated over a wide range of initial phenol concentrations (0–2000 mg l −1) using Haldane model. The results received in these experiments demonstrated that the Haldane kinetic model adequately described the dynamic behavior of the phenol biodegradation by the strain of C. tropicalis.

Daily consumption of phenolics and total antioxidant capacity from fruit and vegetables in the American diet

AbstractThe daily intake of total phenolics, total flavonoids and antioxidants in the American diet was estimated from the most common 34 fresh fruit and vegetables and their daily consumption data. Among 14 fruit and 20 vegetables, orange contributed the highest amount of total phenolics [117.1 mg gallic acid equivalent (GAE) person−1day−1] and antioxidants [146.6 mg vitamin C equivalents (VCE) person−1day−1]. Orange contributed about 26 and 25% of total phenolics and antioxidant, respectively, in the daily consumption of fruit and vegetables. Apples showed relatively high levels of total phenolics and antioxidant capacity comparable to those of oranges and their phenolics and antioxidants contribution is the second highest. Even though potatoes had lower levels of phenolics and antioxidant capacity, they were third due to the fact that their consumption is the highest (137.9 lb person−1year−1) in the American diet. Although plums and strawberries were ranked as the group with the highest total phenolics and antioxidant capacity among 34 tested fruit and vegetables, their contributions were relatively low due to their lower daily consumption. Generally, the levels of total phenolics, total flavonoids and antioxidant capacity of fruits were higher than those of vegetables. American daily intake of phenolics, flavonoids and antioxidants from fruits and vegetables was estimated to be 450 mg GAE, 103 mg catechin equivalents and 591 mg VCE, respectively. Although we do not yet know the required minimum daily amounts of antioxidants, when we estimate the daily requirement of antioxidants, we must consider not only the antioxidant concentrations of the particular food, but also the daily intakes of the food. Copyright © 2005 Society of Chemical Industry

Pilot scale application of the Membrane Aromatic Recovery System (MARS) for recovery of phenol from resin production condensates

This paper describes the application of the Membrane Aromatic Recovery System (MARS) to the recovery of phenol from wastewater streams arising from a phenolic resins production plant. These wastewater streams typically contain between 2 and 8 wt.% phenol, and their detoxification has a significant economical and environmental impact, since about 30% of the global phenol consumption is intended for phenolic resins synthesis (annual production of approximately 3 million metric tons resin). A MARS pilot plant unit operating in batch mode was installed at a United Kingdom resin manufacturing site, and average efficiencies of 94 and 84%, for the phenol extraction and the phenol recovery stages, respectively, were achieved. The final MARS product, an organic phase, composed of 77–80 wt.% phenol and 20–23 wt.% water, was recycled back to the original manufacturing process and successfully used as a reagent for resin production. The phenol content in the discharged wastewater stream was successfully reduced to 0.1–0.3 wt.%, sufficiently low to allow further detoxification by a destructive process, such as biotreatment or chemical oxidation. The influence of different parameters, such as stripping solution pH and neutralizing HCl solution concentration on the process performance was evaluated. Scale up effects on the mass transfer at the extraction stage were also analysed on the basis of the liquid film theory and the resistances in series approach.

Density functional theory applied to thermochemical calculations for phenol reactions

Phenol recovery from wastewaters is a crucial task in the chemical process area, for both economical and environmental reasons, since phenol is a high added value product but, also, highly toxic. Reactive distillation is being proposed as an alternative process for eliminating phenol from water. However, before studying the process, it is necessary to derive a suitable phenol reaction and, also, to calculate its equilibrium constants, since no such values are reported in the open literature. In this work, Benson's method and molecular modeling are applied to calculate thermochemical values for phenol reactions with acetic acid (phenol acylation) and with acetic anhydride (phenol esterification). However, Benson's method presented limitation for calculation of the thermochemical values for the proposed reactions, because some of the additivity groups are not found in published tables. Using molecular modeling, calculations were carried out at several temperatures. Results from density functional theory (DFT) indicate that the equilibrium constant for phenol esterification is greater than the one for phenol acylation and, thus, the former reaction is more suitable in terms of consumption of phenol. Moreover, it was observed that the acylation reaction reaches high conversions only at high temperatures.

Bioavailability and antioxidant effects of olive oil phenols in humans: a review.

We reviewed the bioavailability and antioxidant effects of phenols from extra virgin olive oil. We searched the MEDLINE database for the years 1966-2002. To review the bioavailability of olive oil phenols, we selected animal and human studies that studied the absorption, metabolism, and urinary excretion of olive oil phenols. We also estimated the intake of the various phenols in the Mediterranean area. To review the antioxidant effects of olive oil phenols, we included human and animal studies on the effect of olive oil phenols on markers of oxidative processes in the body. We excluded studies without a proper control treatment and studies in which the antioxidant effects of phenols could not be disentangled from those of the fatty acid composition of olive oil. Bioavailability studies in humans show that the absorption of olive oil phenols is probably larger than 55-66 mol%, and that at least 5% is excreted in urine as tyrosol and hydroxytyrosol. Animal studies suggest that phenol-rich olive oil lowers oxidisability of ex vivo low-density lipoprotein (LDL) particles or lowers markers in urine of oxidative processes in the body. In five out of seven human studies, however, these effects of phenols were not found. There are no data on the phenol concentrations in plasma that are attainable by intake of olive oil. We estimated that 50 g of olive oil per day provides about 2 mg or approximately 13 micromol of hydroxytyrosol-equivalents per day, and that the plasma concentration of olive oil phenols with antioxidant potential resulting from such an intake can be at most 0.06 micromol/l. This is much lower than the minimum concentrations of these phenols (50-100 micromol) required to show antioxidant activity in vitro. Although phenols from olive oil seem to be well absorbed, the content of olive oil phenols with antioxidant potential in the Mediterranean diet is probably too low to produce a measurable effect on LDL oxidisability or other oxidation markers in humans. The available evidence does not suggest that consumption of phenols in the amounts provided by dietary olive oil will protect LDL against oxidative modification to any important extent.

Quercetin Protects Against Linoleic Acid-Induced Porcine Endothelial Cell Dysfunction

Consumption of plant phenolics, such as quercetin, may be associated with decreased risk of cardiovascular disease by stabilizing and protecting vascular endothelial cells against oxidative and proinflammatory insults. The present study focused on the effect of quercetin on linoleic acid-induced oxidative stress and the inflammatory pathways of nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1). Because the transcription factor peroxisome proliferator activated receptor gamma (PPARgamma) was reported to downregulate inflammatory pathways, we further investigated the effect of quercetin on PPARgamma. Porcine pulmonary-arterial endothelial cells were activated with linoleic acid in the presence or absence of quercetin. Oxidative stress was markedly induced by endothelial cell exposure to linoleic acid and diminished by treatment with quercetin as measured via the oxidation of 2',7'-dichlorofluorescin. Quercetin reduced linoleic acid-mediated binding activity of NF-kappaB and AP-1 and mRNA levels of inflammatory genes such as interleukin-6 (IL-6) and vascular cell adhesion molecule-1 (VCAM-1). Cotreatment of linoleic acid plus quercetin or vitamin E also decreased linoleic acid-induced binding activity of PPARgamma. These data suggest that quercetin has potent antioxidative and anti-inflammatory properties and protects endothelial cells against linoleic acid-mediated cell dysfunction.

Growth on Phenol at Chemostress Levels Amplifies the Expression of the Phenol Degradation Pathway in Acinetobacter calcoaceticus

AbstractBacteria often use pollutants as sole carbon and energy sources. However, if they are toxic and the concentrations are high these compounds inhibit growth, and eventually poison the biocatalysts. In order to identify mechanisms contributing to stability, the protein patterns of Acinetobacter calcoaceticus during growth on potentially toxic phenol were analysed using two‐dimensional gel electrophoresis. Enzymes involved in the catabolism or assimilation of phenol, such as phenol monooxygenase and catechol 1,2‐dioxygenase, were induced at a more than twofold level in response to long‐term exposure to high concentrations of the compound serving as the sole carbon and energy source. This would have clear adaptive benefits, since increased rates of consumption of phenol would reduce the susceptibility of Acinetobacter calcoaceticus to phenol poisoning. In contrast, transient induction of only one heat shock protein and one oxidative stress protein was detected during long‐term exposure to high concentrations of phenol.

Effect of phenol and derivatives on atom transfer radical polymerization in the presence of air

AbstractThe various phenolic compounds in conjunction with Cu(II) or Cu(I)‐N,N,N′,N″,N″‐pentamethyl diethylenetriamine (PMDETA) complexes are used to initiate atom transfer radical polymerization (ATRP) of methyl methacrylate, styrene, and methyl acrylate in the presence of a limited amount of air at temperatures in the range of 80–110 °C. Meanwhile, an effort is directed toward the elucidation of the role of phenol and derivatives in ATRP catalyzed by Cu(II)/PMDETA. The catalytic sequence involves the formation of Cu(I) by electron transfer from phenol to Cu(II); Cu(I) so formed can then react in two distinctly different ways: with organic halide to form a propagating radical or with oxygen to form copper salt in its higher oxidation state; and regeneration of Cu(I) by excess phenol. Such regeneration of Cu(I) would be expected to lead to polymerization as a result of the consumption of oxygen and phenol as well. The phenols with electron releasing groups tended to increase the conversion of the polymerization. In this respect, sodium phenoxide, a more effective additive was found, whereas p‐nitro phenol was the least effective. The obtained polymers displayed the common features of a controlled polymerization such as molecular weight control and low polydispersity index value (Mw/Mn < 1.5). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 351–359, 2004

Phenol degradation by a Graphium sp. FIB4 isolated from industrial effluents.

In this work, we show that the fungal strain Graphium sp. FIB4 was able to use phenol as the sole carbon source. Higher degradation of phenol was accomplished by alginate-immobilized mycelial mass than by mycelial suspensions of Graphium sp. FIB4. Free mycelium exhibited higher degradation rates when compared with the alginate-immobilized mycelium in the presence of 14 mM of phenol or less. Above this concentration, degradation rates by free mycelium decreased and the immobilized mycelium showed higher values. The maximum degradation rate for 8 mM phenol was found to be 20.13 mg/l x h by free mycelia and 16.24 mg/l x h by immobilized mycelial mass in the presence of 18 mM phenol. When the fungus was grown on medium without phenol, catechol 1,2-dioxygenase activity was not detected. This enzyme activity was induced at phenol concentrations as low as 0.05 mM and up to 6 mM at 24 h incubation at 30 degrees C, suggesting that catechol was oxidized by the ortho type of ring fission. Addition of glucose reduced phenol consumption rate, and both substrates were used simultaneously. Glucose concentrations higher than 0.075% repressed the induction of phenol oxidation by Graphium sp. FIB4 grown on glucose. But glucose did not fully repress utilization of phenol by phenol-pre-induced cells. Immobilization and addition of calcium and barium ions were detrimental to the stability of catechol 1,2-dioxygenase activity and phenol degradation by Graphium sp. FIB4.

Nickel particle size effects in catalytic hydrogenation and hydrodechlorination: phenolic transformations over nickel/silica

The gas phase hydrodechlorination of 2,4-dichlorophenol (2,4-DCP) and 2-chlorophenol (2-CP) has been studied over three series of Ni/SiO2 catalysts prepared by three different methods, i.e. (i) impregnation with nickel nitrate, (ii) impregnation with nickel ethanediamine and (iii) deposition-precipitation. This has led to catalysts with a wide range of Ni loadings (0.7–20.9% w/w Ni) and an average Ni particle size from 1.4 to 16.8 nm. The chloroarene was continuously fed to the reactor as a methanolic or aqueous solution (with subsequent vaporisation) where consistently higher hydrodechlorination activities were associated with the aqueous feed due to methanol/support interactions that served to inhibit the surface hydrogenolytic reaction. Hydrodechlorination of 2-CP yielded the fully dechlorinated aromatic product (phenol) and HCl while 2,4-DCP also yielded the partially dechlorinated (2-CP) aromatic product. There was no detectable aromatic ring reduction and the hydrodechlorination kinetics can be represented by a pseudo-first order approximation. Structure sensitivity has been conclusively established where the specific Cl removal was consistently greater with an increase in the average Ni particle diameter. The specific hydrodechlorination rate for 2,4-DCP was lower than that for 2-CP, diagnostic of a deactivating electronic effect associated with the Cl substituent(s) and this was manifested by higher apparent activation energies (ΔEa) for the 2,4-DCP reaction; the ΔEa values were unaffected by catalyst preparation/activation/Ni loading. The direct hydrogenation of phenol (as feed) was largely insensitive to Ni particle size albeit there was a discernible decrease in specific phenol consumption over average Ni diameters less than ca. 3 nm. Hydrogenation selectivity remained unchanged and cyclohexanol was the predominant product irrespective of Ni loading or synthesis route.

Some features of phenolic inhibitor consumption in oxidized polypropylene in the presence of synergists–hydroperoxide decomposers

AbstractThe influence of sulfur and phosphors containing substances, hydroperoxide decomposers, on the kinetics of the consumption of two phenolic antioxidants in polypropylene (PP) was studied. The induction periods of PP autoxidation at 130°C were measured in the presence of inhibiting compositions that consisted of phenolic inhibitors and decomposers of hydroperoxide. The obtained results indicated that the influence of the hydroperoxide decomposer became significant when the concentration of the phenolic antioxidant became close to a critical value. It was shown also that the influence of the hydroperoxide decomposer significantly depended on the mechanism of the phenolic inhibitor transformation: first of all, on the nature of its transformation products. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2226–2229, 2003

Ozonolysis of phenols in aqueous solution.

In the ozonolysis of phenol in aqueous solution at pH 3, 7 and 10 the following products were quantified: catechol, hydroquinone, 1,4-benzoquinone, cis,cis-muconic acid, H2O2, 2,4-dihydroxybiphenyl and 4,4-dihydroxybiphenyl. At pH 10, material balance (products vs. phenol consumption) is obtained. Singlet dioxygen, O2(1 delta g), and .OH are formed as short-lived intermediates. The precursor of the latter, O3.-, and a phenoxyl radical is suggested to arise from electron transfer from phenol/phenolate to ozone. Addition of .OH to phenol gives rise to dihydroxycyclohexadienyl radicals which add dioxygen and eliminate HO2. thereby forming catechol/hydroquinone. In competition and catalysed by H+ and OH-, the dihydroxycyclohexadienyl radical eliminates water yielding a phenoxyl radical. At pH 10, they readily oxidize catechol and hydroquinone. This reforms phenol (accounting for the low phenol consumption) and yields higher-oxidised products, eventually 1,4-benzoquinone. cis,cis-Muconic acid can be accounted for by the Criegee mechanism, while O2(1 delta g) is released on the way to (some of the) catechol and hydroquinone. Similar reactions proceed with hydroquinone (products: 1,4-benzoquinone, 2-hydroxy-1,4-benzoquinone and H2O2, with high yields of O2(1 delta g) and .OH) and with catechol (products: 2-hydroxy-1,4-benzoquinone, cis,cis-muconic acid, H2O2 with high yields of O2(1 delta g) and .OH). Material balance is not obtained for these two systems. Pentachlorophenolate, pentabromophenolate and 2,4,6-triiodophenolate ions give rise to halide ions, O2(1 delta g) (58%/48%/10%) and .OH (27%/2%/0%). It is suggested that together with O2(1 delta g) the corresponding ortho- and para-quinones plus a halide ion are formed. Further halide ion is released upon the hydrolysis of these and other products. For pentachlorophenolate the material balance with respect to the short-lived intermediates is 85%. With the bromo- and iodophenolates the O2(1 delta g) yields are substantially lowered, most likely due to release of triplet (ground state) dioxygen induced by the heavy atom effect.

Predicting the hydroxymethylation rate of phenols with formaldehyde by molecular orbital calculation

The rates (k) of hydroxymethylation of phenol, resorcinol, phloroglucinol, and several methylphenols in diluted 10% dimethylformamide aqueous alkaline solution were calculated based on the consumption of phenols and formaldehyde. Thek values of phloroglucinol and resorcinol relative to that of phenol were about 62000 and 1200 times, respectively. The phenols that have methyl or hydroxyl groups at the C-3 or C-5 position (or both) have larger rate constants than phenols with substituents at other positions. Several kinds of atomic charge of the carbons on the aromatic ring of phenols were calculated using the semiempirical orab initio method. The correlations between the averagek (Ave.k) and average electrostatic charges (Ave.q) at the carbons were fairly good. Highest occupied molecular orbitals (HOMO) were observed. The best correlation between Ave.k and Ave.q was obtained when diphenols and triphenols were assumed to exist in solution as their respective di-anion.

Biodegradation of dimethylphenols by bacteria with different ring-cleavage pathways of phenolic compounds.

The biodegradation of 3,4, 2,4, 2,3, 2,6 and 3,5-dimethylphenol in combination with phenol and p-cresol by axenic and mixed cultures of bacteria was investigated. The strains, which degrade phenol and p-cresol through different catabolic pathways, were isolated from river water continuously polluted with phenolic compounds of leachate of oil shale semicoke ash heaps. The proper research of degradation of 2,4 and 3,4-dimethylphenol in multinutrient environments was performed. The degradation of phenolic compounds from mixtures indicated a flux of substrates into different catabolic pathways. Catechol 2,3-dioxygenase activity was induced by dimethylphenols in Pseudomonas mendocina PC1, where meta cleavage pathway was functional during the degradation of p-cresol. In the case of strains PC18 and PC24 of P. fluorescens, the degradation of p-cresol occurred via the protocatechuate ortho pathway and the key enzyme of this pathway, p-cresol methylhydroxylase, was also induced by dimethylphenols. 2,4 and 3,4-dimethylphenols were converted into the dead-end products 4-hydroxy-3-methylbenzoic acid and 4-hydroxy-2-methylbenzoic acid. In the degradation of 3,4-dimethylphenol, the transient accumulation of 4-hydroxy-2-methylbenzaldehyde repressed the consumption of phenol from substrate mixtures. A mixed culture of strains with different catabolic types made it possible to overcome the incompatibilities at degradation of studied substrate mixtures.

Expanded Application of a Two‐Phase Partitioning Bioreactor through Strain Development and New Feeding Strategies

This research demonstrated the microbial treatment of concentrated phenol wastes using a two-phase partitioning bioreactor (TPPB). TPPBs are characterized by a cell-containing aqueous phase and an immiscible and biocompatible organic phase that partitions toxic substrates to the cells on the basis of their metabolic demand and the thermodynamic equilibrium of the system. Process limitations imposed by the capability of wild-type Pseudomonas putida ATCC 11172 to utilize long chain alcohols were addressed by strain modification (transposon mutagenesis) to eliminate this undesirable biochemical characteristic, enabling use of a range of previously bioavailable organics as delivery solvents. Degradation of phenol in a system with the modified strain as catalyst and industrial grade Adol 85 NF (primarily oleyl alcohol) as the solvent was demonstrated, with the system ultimately degrading 36 g of phenol within 38 h. Volumetric phenol consumption rates by wild type P. putida ATCC 11172 and the genetically modified derivative revealed equivalent phenol degrading capabilities (0.49 g/L x h vs 0.47 g/L x h respectively, in paired fermentations), with the latter presenting a more efficient remediation option due to decreased solvent losses arising from the modified strain's forced inability to consume the delivery solvent as a substrate. Two feeding strategies and system configurations were evaluated to expand practical applications of TPPB technology. The ability to operate with a lower solvent ratio over extended periods revealed potential for long-term application of TPPB to the treatment of large masses of phenol while minimizing solvent costs. Repeated recovery of 99% of phenol from concentrated phenol solutions and subsequent treatment within a TPPB scheme demonstrated applicability of the approach to the remediation of highly contaminated "effluents" as well as large masses of bulk phenol. Operation of the TPPB system in a dispersed manner, rather than as two distinct phases, resulted in volumetric consumption rates similar to those previously achieved only in systems operated with enriched air.

Phenol antioxidant quantity and quality in foods: fruits.

The free and bound phenols have been measured in 20 fruits commonly consumed in the American diet. Phenols were measured colorimetrically using the Folin-Ciocalteu reagent with catechin as the standard after correction for ascorbic acid contribution. On a fresh weight basis, cranberry had the highest total phenols, and was distantly followed by red grape. Free and total phenol quality in the fruits was analyzed by using the inhibition of lower density lipoprotein oxidation promoted by cupric ion. Ascorbate had only a minor contribution to the antioxidants in fruits with the exception of melon, nectarine, orange, white grape, and strawberry. The fruit extracts' antioxidant quality was better than the vitamin antioxidants and most pure phenols, suggesting synergism among the antioxidants in the mixture. Using our assay, fruits had significantly better quantity and quality of phenol antioxidants than vegetables. Fruits, specifically apples and cranberries, have phenol antioxidants that can enrich lower density lipoproteins and protect them from oxidation. The average per capita consumption of fruit phenols in the U.S. is estimated to be 255 mg/day of catechin equivalents.

Fate of apple peel phenolics during cool storage.

Consumption of certain phenolics in the diet is considered beneficial to human health. In this study, individual phenolics were measured by diode-array HPLC at monthly intervals in the peel of Granny Smith, Lady Williams, and Crofton apple cultivars stored in air at 0 degrees C for 9 months. The concentrations of total phenolics significantly differed among the cultivars examined, with Lady Williams peel having significantly more phenolics (over 4000 microg x g(-1) peel fresh weight) than Crofton (2668 microg x g(-1) peel fresh weight) and Granny Smith, which had the lowest concentration of total phenolics (1275 microg x g(-1) peel fresh weight). There were also significant differences in individual phenolics among cultivars and during storage. Quercetin glycosides were the only flavonols identified, with quercetin rhamnoglucoside being the most abundant phenolic in the peel. Chlorogenic acid was the major cinnamic acid derivative, with high concentrations, up to 412 microg x g(-1)) peel fresh weight, in Crofton peel. A pre-storage diphenylamine (DPA) treatment had few significant effects on peel phenolic metabolism. Where differences did occur, fruit treated with DPA retained higher concentrations of total peel phenolics during storage than fruit not treated with DPA. Storage of all cultivars for up to 9 months in air at 0 degrees C induced few significant changes in the peel phenolic concentrations. This indicates that phenolic metabolism in apple peel is relatively stable, and the health benefits of phenolics in apple peel should be maintained during long-term storage.