Antioxidant activity of pomegranate juice and its relationship with phenolic composition and processing

The antioxidant activity of pomegranate juices was evaluated by four different methods (ABTS, DPPH, DMPD, and FRAP) and compared to those of red wine and a green tea infusion. Commercial pomegranate juices showed an antioxidant activity (18-20 TEAC) three times higher than those of red wine and green tea (6-8 TEAC). The activity was higher in commercial juices extracted from whole pomegranates than in experimental juices obtained from the arils only (12-14 TEAC). HPLC-DAD and HPLC-MS analyses of the juices revealed that commercial juices contained the pomegranate tannin punicalagin (1500-1900 mg/L) while only traces of this compound were detected in the experimental juice obtained from arils in the laboratory. This shows that pomegranate industrial processing extracts some of the hydrolyzable tannins present in the fruit rind. This could account for the higher antioxidant activity of commercial juices compared to the experimental ones. In addition, anthocyanins, ellagic acid derivatives, and hydrolyzable tannins were detected and quantified in the pomegranate juices.     

In vitro metabolism of plant lignans: new precursors of mammalian lignans enterolactone and enterodiol.

The metabolism of the plant lignans matairesinol, secoisolariciresinol, pinoresinol, syringaresinol, arctigenin, 7-hydroxymatairesinol, isolariciresinol, and lariciresinol by human fecal microflora was investigated to study their properties as mammalian lignan precursors. The quantitative analyses of lignan precursors and the mammalian lignans enterolactone and enterodiol were performed by HPLC with coulometric electrode array detector. The metabolic products, including mammalian lignans, were characterized as trimethylsilyl derivatives by gas chromatography-mass spectrometry. Matairesinol, secoisolariciresinol, lariciresinol, and pinoresinol were converted to mammalian lignans only. Several metabolites were isolated and tentatively identified as for syringaresinol and arctigenin in addition to the mammalian lignans. Metabolites of 7-hydroxymatairesinol were characterized as enterolactone and 7-hydroxyenterolactone by comparison with authentic reference compounds. A metabolic scheme describing the conversion of the most abundant new mammalian lignan precursors, pinoresinol and lariciresinol, is presented.     

Nondestructive determination of lignans and lignan glycosides in sesame seeds by near infrared reflectance spectroscopy

Sesame (Sesamum indicum L.) contains abundant lignans including lipid-soluble lignans (sesamin and sesamolin) and water-soluble lignan glycosides (sesaminol triglucoside and sesaminol diglucoside) related to antioxidative activity. In this study, near infrared reflectance spectroscopy (NIRS) was used to develop a rapid and nondestructive method for the determination of lignan contents on intact sesame seeds. Ninety-three intact seeds were scanned in the reflectance mode of a scanning monochromator. This scanning procedure did not require the pulverization of samples, allowing each analysis to be completed within minutes. Reference values for lignan contents were obtained by high-performance liquid chromatography analysis. Calibration equations for lignans (sesamin and sesamolin) and lignan glycosides (sesaminol triglucoside and sesaminol diglucoside) contents were developed using modified partial least squares regression with internal cross-validation (n = 63). The equations obtained had low standard errors of cross-validation and moderate R2 (coefficient of determination in calibration). The prediction of an external validation set (n = 30) showed significant correlation between reference values and NIRS predicted values based on the SEP (standard error of prediction), bias, and r2 (coefficient of determination in prediction). The models developed in this study had relatively higher values (more than 2.0) of SD/SEP(C) for all lignans and lignan glycosides except for sesaminol diglucoside, which had a minor amount, indicating good correlation between the reference and the NIRS estimate. The results showed that NIRS, a nondestructive screening method, could be used to rapidly determine lignan and lignan glycoside contents in the breeding programs for high quality sesame.     

六种果皮原料果胶的理化及凝胶特性比较

为了解不同品种水果的果皮(柚子皮、西番莲皮、脐橙皮、石榴皮、榴莲皮)以及向日葵盘所提取果胶的理化和质构特性,研究了不同原料果胶的得率、色泽、果胶酸含量、甲氧基含量、酯化度、黏度及质构特性,特别是采用高效液相色谱准确测定了各类果胶的分子量。结果表明:柚子皮、向日葵盘和脐橙皮果胶质量分数较高,分别为18.06%、14.61%和14.43%;西番莲皮果胶质量分数为8.76%;而石榴皮及榴莲皮果胶质量分数较低(均<3%)。从分子量看,石榴皮、脐橙皮果胶分子量较大(>1000kDa),向日葵盘果胶分子量最小(483kDa)。此外,几种果胶的溶胶均属低黏度值果胶(<25厘泊),且在pH值为7.0时黏度最大、在pH值为5.0时黏度最小。结合凝胶质构分析表明:石榴皮果胶分子量最大,凝胶强度最大,但为高甲氧基果胶,且得率较低;而向日葵盘果胶分子量最小,但得率较高,且为低甲基果胶,在非糖及含糖体系中均可形成性能优良的凝胶,因此是生产果胶的良好原料。该文为果胶的生产及应用提供参考。     

Comparative analysis of polyphenolic profiles and antioxidant and antimicrobial activities of tunisian pome fruit pulp and peel aqueous acetone extracts

Pome trees, apple, pear, and quince, are classified into the subfamily Pomoideae, belonging to the Rosaceae family. Their autumnal fruits are consumed worldwide in different forms, that is, fresh or transformed into jams, jelly, juices, etc. Their well-established beneficial properties to human health were found mainly related to their phenolic content. Pulp and peel aqueous acetone extracts obtained from Tunisian fruits at commercial maturity were comparatively evaluated for their phenolic profiles and antioxidant and antimicrobial potentials. The phenolic compounds present in the extracts were identified and quantified using RP-HPLC-DAD and ESI-MS techniques. Significant differences in the chromatographic profiles among these fruits, as well as between pulp and peel extracts of each fruit, were observed. Quince, followed by 'Red Delicious', peel extracts showed the highest phenolic content (160.33 and 110.90 mg/100 g of fresh weight). The stronger inhibitory effect on DPPH radicals corresponded to those obtained from peel materials. A comparative analysis of the antimicrobial potential against a range of microorganism strains was also carried out. Staphylococcus aureus, Pseudomonas aeruginosa, and Bacillus cereus were the most sensitive to the active extracts. Among the examined phenolic extracts, 'Red Delicious' and quince peels showed the highest effects for inhibiting bacteria growth. Minimum inhibitory and bactericide concentrations ranged from 10(2) to 10(4) microg of polyphenol/mL. Red skin apple and quince peels could be of great interest as important antioxidant and antimicrobial polyphenol sources.     

Phloroglucinol from phlorin hydrolysis for testing quality of commercial orange juices and beverages

The European Association of Juices and Nectars Producers (AIJN) is evaluating the opportunity to introduce the content of phlorin (3,5-dihydroxyphenyl beta-D-glucopyranoside), a peel marker for oranges, as a parameter for testing the quality of orange juices. Because of the lack of a commercial standard of phlorin and its laborious isolation procedures, in this contribution is developed a simple and reliable method for measuring the phlorin level as the corresponding aglycon phloroglucinol, obtained after a total enzymatic hydrolysis of the sample. The method was applied to the quantification of phloroglucinol in several industrial and commercial blond and pigmented orange juices and beverages based on 12% orange juice. Under the same extraction procedure, the phloroglucinol content in the pigmented juices was higher than in the blond ones. No significant difference was obtained between not from concentrate juices and reconstituted from concentrate juices. The marker amount increases in the highly processed orange fruits and in the byproducts of citrus processing due to the contact of the juice with the albedo, which is the major source of phlorin. In orange-based beverages the phloroglucinol content revealed a large heterogeneity and a poor quality of the raw juices used.     

Identification and stereochemical characterization of lignans in flaxseed and pumpkin seeds

Phytoestrogens of the lignan type are widely distributed in plant-derived food items and are believed to protect against hormone-dependent cancer. The richest known dietary source of lignans is flaxseed. Flaxseed has been reported to contain glycosides of secoisolariciresinol as the major lignan, together with small amounts of matairesinol, isolariciresinol, and pinoresinol. Secoisolariciresinol, but none of the other lignans, has so far been identified in pumpkin seeds. In the present study, two different methods for the hydrolysis of lignan glycosides are compared. Artifact formation and loss of lignans under acidic conditions were observed. Lariciresinol was identified by GC-MS analysis in two different types of flaxseed (Linum usitatissimum L. and Linum flavum L.) and in pumpkin seeds (Cucurbita pepo L.) for the first time. Likewise, the novel lignan demethoxy-secoisolariciresinol was tentatively identified in the flaxseed samples. Stereochemical analysis by chiral HPLC of several lignans isolated from flaxseed showed that secoisolariciresinol, matairesinol, and lariciresinol consisted predominantly of one enantiomer.     

Phlorin screening in various citrus species and varieties

Phlorin (3,5-dihydroxyphenyl beta-D-glucopyranoside), an orange peel marker, has been searched in 45 species and varieties of Citrus. The phlorin content was determined by high-pressure liquid chromatography in juices and aqueous peel extracts of these different fruits. The phlorin content in C. reticulata peel extract varies from 0 to 1012 mg L(-)(1) with a mean of 162 mg L(-)(1). On the contrary, phlorin was not found in mandarin and clementine juices except for mandarin "Commune" and "Beauty" (33 and 30 mg L(-)(1), respectively). In the 14 species of oranges and varieties, phlorin was detected in juices and peel extracts with a mean of 22 and 492 mg L(-)(1), respectively, while for grapefruits, means were 108 mg L(-)(1) in juices and 982 mg L(-)(1) for peel extracts. Tangors and tangelos which are hybrids (C. reticulata x C. sinensis and C. reticulata x C. paradisi, respectively) are characterized by the systematic presence of phlorin in peels (mean: 406 and 659 mg L(-)(1), respectively) while in juices its presence could be variable (0-73 mg L(-)(1)). These heterogeneity and values may be explained by the genetic variability of these hybrids and the phlorin content of their parentage group.     

不同氮肥用量对石榴果实产量和品质的影响

以‘秋艳’石榴为试验材料,研究了不同氮肥用量对其果实产量和品质的影响。结果表明,施用氮肥可显著提高石榴果实产量,适量施用氮肥可增加石榴果实可溶性固形物、Vc、糖含量,降低石榴果实酸含量,提高石榴果实糖酸比,改善石榴果实的风味;施用氮肥对石榴百粒重、籽粒硬度无显著影响;石榴籽氮元素含量高于石榴皮,石榴汁中氮含量很低,中高氮处理的石榴汁中氮元素含量显著降低,石榴皮和石榴籽中氮元素含量变化不显著;本试验5年生石榴树纯氮施肥用量宜以0.4 kg·株~(-1)为宜。     

Isolation and characterization of the lignans, isolariciresinol and pinoresinol, in flaxseed meal.

The isolation and characterization of the lignans, isolariciresinol, pinoresinol, secoisolariciresinol, and matairesinol, potent phytoestrogens, from flaxseed meal are described. This is the first report of isolariciresinol and pinoresinol being detected in a food. The extraction method selected combined the removal of the lignan glycosides from the plant matrix with an alcoholic solvent system, followed by acid hydrolysis to release the aglycons. A reversed-phase high-performance liquid chromatography with diode array detection system was used for initial separation and detection of the lignans at 280 nm in the acid-hydrolyzed methanolic extract. Lignan trimethylsilyl ether derivatives were characterized by gas chromatography/mass spectrometry. Secoisolariciresinol is the major lignan in flaxseed; isolariciresinol, pinoresinol, and matairesinol were identified as minor lignan components.     

Nutritive and antioxidative potential of fresh and stored pomegranate industrial byproduct as a novel beef cattle feed

Pomegranate peel is a nutritive-rich byproduct whose amounts are extensively growing due to the exponential increase in the production of pomegranate juice and "ready to eat" arils. Pomegranate peel is a rich source for antioxidants and thus may serve in the prevention of cattle diseases and in the improvement of beef products, making it an attractive component in beef cattle diets. The present study aims to evaluate the effect of commonly used storage practices on the nutritive and antioxidative properties of pomegranate peel. In general, storage conditions preserved most antioxidant capacity. Ensiling ambivalently affected the nutritive values of the peel and promoted increased levels of antioxidative components. In addition to polyphenols, nonphenolic components, such as alpha- and gamma-tocopherols, contributed to the total antioxidative capacity, and several minerals found in the peel added to its nutritional value. Dietary supplementation with fresh peels promoted significant increases in feed intake and alpha-tocopherol concentration in the plasma, with positive tendency toward increased weight gain of bull calves. All in all, the nutritive value and the antioxidant capacity of pomegranate peel turn it into a favorable health-promoting constituent of feedlot beef cattle diet.     

Mass spectrometric detection and formation of D-amino acids in processed plant saps, syrups, and fruit juice concentrates

Liquid and syrupy dietary saps and juices of plant origin, characterized by the presence of large quantities of saccharides (glucose, fructose, or sucrose) and containing amino acids, were analyzed for the presence of D-amino acids using enantioselective gas chromatography-mass spectrometry. D-amino acids were detected in processed saps and juices of trees (maple, palm, birch), fruits (grape, apple, pear, pomegranate, date), and various other plants (agave, beetroot, sugar cane, carob). D-Ala was detected in all plant products and amounted to approximately 34% D-Ala (relative to L-Ala + D-Ala) in Canadian maple syrups, to approximately 13% in palm saps, and to 48 and 13% D-Ala, respectively, in concentrated grape juices (Spanish Arrope and Turkish Pekmez). Varying amounts and kinds of other D-amino acids were also detected. To test the hypothesis that racemization, that is, partial conversion of L-amino acids into their corresponding D-enantiomers, occurs at reversible stages of the Maillard reaction, the Amadori compound fructose-L-phenylalanine was synthesized. On heating at 200 degrees C for 5 (20) min, release of 10.8% (24.2%) D-Phe was detected. From the data it is concluded that the Amadori compounds formed in the course of the Maillard reaction are pecursors of D-amino acids in foodstuffs.     

Dietary alkylresorcinols and lignans in the Spanish diet: development of the alignia database

The intake of alkylresorcinols and lignans in Spain is unknown due to the lack of information on the content of these compounds in particular foods. This paper describes the development of the first alkylresorcinol and lignan database adapted to the Spanish diet, including foods items especially relevant for this population. The values of alkylresorcinols and lignans in common foods and beverages were collected from scientific publications in refereed journals, and other foods particularly consumed in Spain, for which values were not available, were analyzed by standardized protocols and included into the database. The Alignia database presents the content of alkylresorcinols in 88 food items and the lignan content of 593 foods and beverages. Using the database, the intake of lignans in Spain, calculated using data from the Food Composition Panel based on household consumption, was estimated to be 0.76 mg/day.     

EFFECTS OF POTASSIUM NITRATE SPRAYING ON FRUIT CHARACTERISTICS OF ‘MALAS YAZDI’ POMEGRANATE

The present research was carried out to investigate the effects of potassium nitrate on pomegranate fruit quality. Treatments were: 1) control, distilled water was used; 2) potassium nitrate 250 mg L-¹ plus Tween-20 and 3) potassium nitrate 500 mg L-¹ plus Tween-20. All treatments were sprayed on fruits with a diameter of 30 mm. Juice, peel, seed characters, and fruit quality components were evaluated when fruits were harvested. Results indicated that 250 mg L-¹ potassium treatment increased juice volume and weight compared with the control and the 500 mg L-¹ K treatments. As the potassium nitrate level increased, aril length and diameter decreased. Although there was not a significant difference among treatments on titrable acidity and pH contents of fruits, the highest total soluble solids and vitamin C were obtained in the 250 mg L-¹ potassium nitrate treatment when compared with the others. These findings show that applied potassium nitrate significantly influences fruit quality of pomegranate when fruit are in the beginning stages of growth and development.     

Quantification of a broad spectrum of lignans in cereals, oilseeds, and nuts

Twenty-four plant lignans were analyzed by high-performance liquid chromatography-tandem mass spectrometry in bran extracts of 16 cereal species, in four nut species, and in two oilseed species (sesame seeds and linseeds). Eighteen of these were lignans previously unidentified in these species, and of these, 16 were identified in the analyzed samples. Four different extraction methods were applied as follows: alkaline extraction, mild acid extraction, a combination of alkaline and mild acid extraction, or accelerated solvent extraction. The extraction method was of great importance for the lignan yield. 7-Hydroxymatairesinol, which has not previously been detected in cereals because of destructive extraction methods, was the dominant lignan in wheat, triticale, oat, barley, millet, corn bran, and amaranth whole grain. Syringaresinol was the other dominant cereal lignan. Wheat and rye bran had the highest lignan content of all cereals; however, linseeds and sesame seeds were by far the most lignan-rich of the studied species.     

Linalool in orange juice: origin and thermal stability

Linalool concentrations were determined in juice from three groups of 60 Valencia oranges using pentane:ether extraction and high-resolution capillary GC. The outer peel (flavedo) was removed from one group. The other two groups retained their peel intact. Juice was extricated from the halved fruits of the flavedo-less group and from one of the peel-intact groups using a hand reamer. A peel-cutting/macerating juice extractor was used for the other peel-intact group. Linalool concentrations were 0.004 mg/L in peeled fruit juice and 0.020 and 0.106 mg/L for hand-reamed and mechanically extracted peel-intact juice, respectively. Juice from peeled fruit contained significantly (P < 0.05) less linalool than peel-intact juice. Approximately 80% of the total juice linalool content was associated with peel using reamer design, and 96% was associated with peel-cutting/macerating design. Linalool increased with increasing peel oil levels; however, the increases were not proportionate. Since all commercial juices are mechanically extracted, the vast majority of linalool in commercial orange juice originates from the peel and not from the juice vesicle cytoplasm. Juice from peel-macerated, mechanically extracted fruit increased from 0.106 to 0.134 mg/kg after thermal processing, whereas juice from reamer extraction was essentially unchanged.     

石榴皮提取液对草莓的保鲜效果

为了发展草莓贮藏保鲜的新技术和有效利用石榴皮资源,以新鲜草莓为材料,在贮藏前分别经过1.25%壳聚糖溶液（T1）、1%石榴皮提取液（T2）、1.25%壳聚糖石榴皮提取物复合溶液（T3）浸泡处理,以蒸馏水浸泡作为对照（CK）,通过对其在贮藏期相关品质指标（质量损失率、软化腐烂率、可溶性固形物质量分数、可滴定酸质量分数、Vc质量分数、丙二醛（MDA）含量）的测定,比较了3种处理溶液的保鲜效果。结果显示,T1、T2、T3处理均降低了草莓果实质量损失率、软化腐烂率和MDA含量,延缓了果实可滴定酸、可溶性固形物和Vc质量分数的下降,其中T3处理效果明显好于T1和T2处理,T3处理可使在室温下放置的草莓保鲜期延长1～2 d。结果表明石榴皮提取液用于草莓保鲜可行,与一定浓度的壳聚糖配制的复合保鲜液保鲜效果更理想。     

Analysis of alternariol and alternariol monomethyl ether on flavedo and albedo tissues of tangerines (Citrus reticulata) with symptoms of alternaria brown spot

A method was developed for the quantification of alternariol and alternariol monomethyl ether on tangerines with and without symptoms of Alternaria brown spot disease. The method employs solid-phase extraction for cleanup, followed by high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) for detection. This method was validated on flavedo (exocarp or epicarp, exterior yellow peel) and on albedo tissue (mesocarp, interior white peel). An excellent linearity over a range of 0.50-20.0 mg/kg was achieved, with r2 >or= 0.997. The limits of detection (LOD) and quantification (LOQ) were fewer than 0.13 and 0.50 microg/kg, respectively. The relative standard deviations (RSDs) were 相似文献   

Studies on the antioxidant activity of pomegranate (Punica granatum) peel and seed extracts using in vitro models.

Antioxidant-rich fractions were extracted from pomegranate (Punica granatum) peels and seeds using ethyl acetate, methanol, and water. The extracts were screened for their potential as antioxidants using various in vitro models, such as beta-carotene-linoleate and 1,1-diphenyl-2-picryl hydrazyl (DPPH) model systems. The methanol extract of peels showed 83 and 81% antioxidant activity at 50 ppm using the beta-carotene-linoleate and DPPH model systems, respectively. Similarly, the methanol extract of seeds showed 22.6 and 23.2% antioxidant activity at 100 ppm using the beta-carotene-linoleate and DPPH model systems, respectively. As the methanol extract of pomegranate peel showed the highest antioxidant activity among all of the extracts, it was selected for testing of its effect on lipid peroxidation, hydroxyl radical scavenging activity, and human low-density lipoprotein (LDL) oxidation. The methanol extract showed 56, 58, and 93.7% inhibition using the thiobarbituric acid method, hydroxyl radical scavenging activity, and LDL oxidation, respectively, at 100 ppm. This is the first report on the antioxidant properties of the extracts from pomegranate peel and seeds. Owing to this property, the studies can be further extended to exploit them for their possible application for the preservation of food products as well as their use as health supplements and neutraceuticals.     

Oxidative metabolites of the mammalian lignans enterodiol and enterolactone in rat bile and urine

Recent studies have shown that the mammalian lignans enterodiol (END) and enterolactone (ENL) are biotransformed in vitro by hepatic microsomes from rats and humans to various metabolites carrying one additional hydroxy group either at the aromatic or at the aliphatic moiety. To clarify whether these metabolites are also formed in vivo, each lignan was administered intraduodenally at a dose of 10 mg/kg of bw to bile duct-catheterized female Wistar rats and the 6 h bile analyzed by HPLC and GC-MS. With END-dosed rats, three products of aromatic and two of aliphatic monohydroxylation were found, whereas six aromatic and five aliphatic monohydroxylated biliary metabolites were detected after administration of ENL. The metabolites hydroxylated at the aromatic rings were unequivocally identified by comparison with synthetic reference compounds. The structures of the in vivo metabolites arising from aliphatic hydroxylation could not be completely elucidated; they were identical with some of the formerly reported microsomal products according to GC retention times and mass spectra. Significant amounts of most of the metabolites of the mammalian lignans identified in bile were also found in the urine of female rats after oral administration of 10 mg/kg of bw END or ENL and in the urine of female and male Wistar rats after they had been fed a diet containing 5% flaxseed. Thus, the mammalian lignans END and ENL give rise to several hydroxylated metabolites in vivo, which may contribute to the biological effects of these important food constituents.