Free hydroxycinnamic acids, lycopene, and color parameters in tomato cultivars

Concentrations of antioxidant compounds (total phenolic compounds, free hydroxycinnamic acids, and lycopene) and color parameters ( a*, b*, and L*) were determined in 167 tomato samples belonging to five cultivars (Dorothy, Boludo, Dunkan, Dominique, and Thomas) produced on the island of Tenerife. Chlorogenic, caffeic, p-coumaric, and ferulic acids were identified and quantified in the tomato samples. Chlorogenic acid had the highest mean concentration, whereas the p-coumaric was not detected in almost half of the tomato samples. The cultivar, cultivation method, and production region had little influence on the concentration of analyzed parameters. Considerable seasonal variations in the levels of these parameters were observed. Many correlations were observed between the antioxidant compounds and color parameters. The tomato samples tended to be differentiated according to the sampling period when discriminant analysis was applied.     

Antioxidant and antimelanogenic activities of polyamine conjugates from corn bran and related hydroxycinnamic acids

The antioxidant activity of three major polyamine conjugates, N,N'-dicoumaroyl-putrescine (DCP), N-p-coumaroyl-N'-feruloylputrescine (CFP), and N,N'-diferuloyl-putrescine (DFP) isolated from corn bran, and their related hydroxycinnamic acids, p-coumaric acid and ferulic acid, were evaluated by three antioxidant in vitro assay systems, including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and superoxide and hydroxyl radicals generated by enzymatic and nonenzymatic reactions. Additionally, five phenolic compounds were evaluated for melanogenesis inhibitory activity using mushroom tyrosinase and B16 melanoma cells. Most of the phenolic compounds significantly scavenged DPPH, superoxide, and hydroxyl radicals in a dose-dependent manner. Particularly, DFP showed potent DPPH (IC50 = 38.46 microM) and superoxide (IC50 = 291.62 microM) radical scavenging activities, while DCP exhibited the strongest hydroxyl radical scavenging activity (IC50 = 120.55 microM). CFP also exerted moderate DPPH, superoxide, and hydroxyl radical scavenging activities. Meanwhile, DCP (IC50 = 181.73 microM) showed potent tyrosinase inhibitory activity toward l-tyrosine as the substrate, whereas DFP (IC50 = 733.64 microM) significantly inhibited melanin synthesis in B16 melanoma cells. These current results indicate that these three polyamine conjugates from corn bran may be useful potential sources of natural antioxidants and skin-whitening agents.     

Uptake and metabolism of hydroxycinnamic acids (chlorogenic, caffeic, and ferulic acids) by HepG2 cells as a model of the human liver

Hydroxycinnamic acids are antioxidant polyphenols common in the human diet, although their potential health benefits depend on their bioavailability. To study the hepatic uptake and metabolism, human hepatoma HepG2 cells were incubated for 2 and 18 h with caffeic, ferulic, and chlorogenic acids. Moderate uptake of caffeic and ferulic acids was observed versus a low absorption of chlorogenic acid, where esterification of the caffeic acid moiety markedly reduced its absorption. Methylation was the preferential pathway for caffeic acid metabolism, along with glucuronidation and sulfation, while ferulic acid generated glucuronides as the only metabolites. Ferulic acid appeared to be more slowly taken up and metabolized by HepG2 cells than caffeic acid, with 73% and 64% of the free, nonmetabolized molecules detected in the culture medium after 18 h, respectively. In conclusion, hydroxycinnamic acids can be metabolized by the liver as suggested by the results obtained using HepG2 cells as a hepatic model system.     

Effect of molecular structure of phenolic families as hydroxycinnamic acids and catechins on their antioxidant effectiveness in minced fish muscle

The antioxidant effectiveness of two different families of phenolic compounds, hydroxycinnamic acids and catechins, added as a power (0.001% w/w) to chilled minced horse mackerel muscle was evaluated. Caffeic acid, chlorogenic acid, o-coumaric acid, and ferulic acid were selected as hydroxycinnamic acids with similar molecular structures. Commercial catechins with different numbers of hydroxylic groups, including catechin, gallocatechin, catechin gallate, and gallocatechin gallate, were also tested. The effectiveness found was individually discussed for each family as a function of the molecular structure. The capacity of hydroxycinnamic acids for donating electrons seems to play the most significant role for retarding the development of rancidity in fish muscle. Conversely, the properties related to the ability for chelating metals and the distribution between oily and aqueous phases were not correlated with the inhibitory activities. Among hydroxycinnamic acids, the results highlighted the potent antioxidant activity of 10 ppm caffeic acid in inhibiting lipid oxidation in fish muscle. Its antioxidant efficacy was similar to that of propyl gallate. Among catechins, catechin showed the highest antioxidant activity. There was an increment of efficacy in fish muscle using concentrations ranging between 10 and 100 ppm of both caffeic acid and catechin.     

Chemical synthesis of hydroxycinnamic acid glucosides and evaluation of their ability to stabilize natural colors via anthocyanin copigmentation

This work describes the chemical synthesis of O-aryl-beta-D-glucosides and 1-O-beta-D-glucosyl esters of hydroxycinnamic acids. In particular, O-aryl-beta-D-glucosides were efficiently prepared via a simple diastereoselective glycosylation procedure using phase transfer conditions. Despite the lability of its ester linkage, 1-O-beta-D-caffeoylglucose could also be obtained using a Lewis acid catalyzed glycosylation step and a set of protective groups that can be removed under neutral conditions. Hydroxycinnamic acid O-aryl-beta-D-glucosides were then quantitatively investigated for their affinity for the naturally occurring anthocyanin malvin (pigment). Formation of the pi-stacking molecular complexes (copigmentation) was characterized in terms of binding constants and enthalpy and entropy changes. The glucosyl moiety did not significantly alter these thermodynamic parameters, in line with a binding process solely involving the polyphenolic nuclei.     

Quantitation of the hydroxycinnamic acid derivatives and the glycosides of flavonols and flavones by UV absorbance after identification by LC-MS

A general approach was developed to quantify hydroxycinnamic acid derivatives and the glycosides of flavonols and flavones using UV molar relative response factors (MRRFs). More than 90 standards were analyzed by LC-MS and divided into five groups based on the λ(max) of their band I absorbance profiles. For each group, a commercially available standard was chosen as the group reference standard. Response factors were determined for each standard in each group as purchased (MRRF) and, when possible, after vacuum drying (MRRF(D)). The MRRF(D) values for 17 compounds whose λ(max) values fell within ±2 nm of the group reference standard were 1.01 ± 0.03. MRRF values for compounds whose λ(max) values fell within ±10 nm of the group reference standard were 0.96 ± 0.13. Group reference standards were used to quantify 44 compounds in Chinese lettuce, red onion, and white tea. This approach allows quantitation of numerous compounds for which there are no standards.     

Variability in the release of free and bound hydroxycinnamic acids from diverse malted barley (Hordeum vulgare L.) cultivars during wort production

Volatile phenols have long been recognized as important flavor contributors to the aroma of various alcoholic beverages. The two main flavor-active volatile phenols in beer are 4-vinylguaiacol and 4-vinylphenol. They are the decarboxylation products of the precursors ferulic acid and p-coumaric acid, respectively, which are released during the brewing process, mainly from malt. In this study, the variability in the release of free and ester-bound hydroxycinnamic acids from nine malted barley ( Hordeum vulgare L.) varieties during wort production was investigated. A large variability between different barley malts and their corresponding worts was observed. Differences were also found between free ferulic acid levels from identical malt varieties originating from different malt houses. During mashing, free hydroxycinnamic acids in wort are both water-extracted and enzymatically released by cinnamoyl esterase activity. Esterase activities clearly differ between different barley malt varieties. Multiple linear regression analysis showed that the release of ferulic acid during mashing did not depend only on the barley malt esterase activity but also on the amount of ester-bound ferulic acid initially present in the wort and on its endoxylanase activity. The study demonstrates the importance of selecting a suitable malt variety as the first means of controlling the final volatile phenol levels in beer.     

Hemoglobin adducts and mercapturic acid excretion of acrylamide and glycidamide in one study population

The aim of this study was to determine the relationship between the oxidative and reductive metabolic pathways of acrylamide (AA) in the nonsmoking general population. For the first time both the blood protein adducts and the urinary metabolites of AA and glycidamide (GA) were quantified in an especially designed study group with even distribution of age and gender. The hemoglobin adducts N-carbamoylethylvaline (AAVal) and N-( R, S)-2-hydroxy-2-carbamoylethylvaline (GAVal) were detected by GC-MS/MS in all blood samples with median levels of 30 and 34 pmol/g of globin, respectively. Concentrations ranged from 15 to 71 pmol/g of globin for AAVal and from 14 to 66 pmol/g of globin for GAVal. The ratio GAVal/AAVal was 0.4-2.7 (median = 1.1). The urinary metabolites were determined by LC-MS/MS. Of all urine samples examined 99% of N-acetyl- S-(2-carbamoylethyl)- l-cysteine (AAMA) levels and 73% of N-( R/ S)-acetyl- S-(2-carbamoyl-2-hydroxyethyl)- l-cysteine (GAMA) levels were above the LOD (1.5 microg/L). Concentrations ranged from 相似文献   

Humic acid reactions with amino acids

Reactions between five humic acids extracted from soils with widely differing pedological histories and 17 amino acids commonly occurring in proteins were investigated in aqueous solutions at pH 3.0 and 6.5. The reactions were affected by: (a) nature of the humic acid: (b) pH of the system: and (c) length of contact. The principal reaction appeared to be the microbiological oxidative degradation of the amino acids leading to the formation of substantial amounts of ammonium. While there was no evidence that the humic acids per se interacted with the amino acids, they did not appear to interfere with the microbiological degradation of the amino acids.     

Reaction of folic acid with reducing sugars and sugar degradation products

The reaction of folic acid with reducing sugars (nonenzymatic glycation) under conditions that can occur during food processing and preparation was studied by high-performance liquid chromatography with diode array detection. N-(p-Aminobenzoyl)-L-glutamic acid, a well-established oxidation product, was detected in the reaction mixtures. Furthermore, a new product was isolated and identified as N2-[1-(carboxyethyl)]folic acid (CEF). CEF was the main product that was formed by the nonenzymatic glycation of folic acid. For preparation, N2-[1-(carboxyethyl)]folic acid was obtained in high yields when folic acid and dihydroxyacetone (DHA), a sugar degradation product, were heated at 100 degrees C in phosphate buffer. Mixtures of folic acid and different sugars or DHA were heated under variation of reaction time and temperature, and CEF was quantified. Up to 50% of the vitamin was converted to CEF, with highest yields formed from maltose (49%) and lactose (43%).     

Hydroxycinnamic acids and ferulic acid dehydrodimers in barley and processed barley

Hydroxycinnamic acid content and ferulic acid dehydrodimer content were determined in 11 barley varieties after alkaline hydrolysis. Ferulic acid (FA) was the most abundant hydroxycinnamate with concentrations ranging from 359 to 624 microg/g dry weight. p-Coumaric acid (PCA) levels ranged from 79 to 260 microg/g dry weight, and caffeic acid was present at concentrations of <19 microg/g dry weight. Among the ferulic acid dehydrodimers that were identified, 8-O-4'-diFA was the most abundant (73-118 microg/g dry weight), followed by 5,5'-diFA (26-47 microg/g dry weight), the 8,5'-diFA benzofuran form (22-45 microg/g dry weight), and the 8,5'-diFA open form (10-23 microg/g dry weight). Significant variations (p < 0.05) among the different barley varieties were observed for all the compounds that were quantified. Barley grains were mechanically fractionated into three fractions: F1, fraction consisting mainly of the husk and outer layers; F2, intermediate fraction; and F3, fraction consisting mainly of the endosperm. Fraction F1 contained the highest concentration for ferulic acid (from 77.7 to 82.3% of the total amount in barley grain), p-coumaric acid (from 78.0 to 86.3%), and ferulic acid dehydrodimers (from 79.2 to 86.8%). Lower contents were found in fraction F2, whereas fraction F3 exhibited the lowest percentages (from 1.2 to 1.9% for ferulic acid, from 0.9 to 1.7% for p-coumaric acid, and <0.02% for ferulic acid dehydrodimers). The solid barley residue from the brewing process (brewer's spent grain) was approximately 5-fold richer in ferulic acid, p-coumaric acid, and ferulic acid dehydrodimers than barley grains.     

Quantitative determination of hydroxycinnamic acids in wheat, rice, rye, and barley straws, maize stems, oil palm frond fiber, and fast-growing poplar wood.

A new method has been developed for the quantitative determination of hydroxycinnamic acids participating in ester or ether linkages to the cell wall polymers. The method is based on mild alkaline hydrolysis followed by acid hydrolysis or mild alkaline hydrolysis, which partially removed esterified phenolic acids, and high-temperature concentrated alkaline treatment, which cleaved both the ester and ether linkages. It was found that traditional mild alkaline hydrolysis and acid hydrolysis released only part of the ester- and ether-linked phenolic acids, respectively. Approximately half (44.0-47.9%) of the total ester-linked p-coumaric acid and 18.2-32.6% of the total esterified ferulic acid remained ester-linked to the mild alkali-soluble lignin polymers, and 55.0-72.0% of the total ether-linked p-coumaric acid and 37.5-53.8% of the total ether-linked ferulic acid remained ether-linked to the solubilized lignin molecules after the acid hydrolysis. To correct this, a second mild alkaline hydrolysis of the alkali-soluble lignin preparations and acid hydrolysis of the solubilized lignin fractions, obtained from the first acid hydrolysis of the cell wall materials, was investigated. On the basis of this new method, a majority of the cell wall p-coumaric acid (55.8-81.5%) was found to be ester-linked to cell wall components, mainly to lignin, and about half of the cell wall ferulic acid is etherified through its phenolic oxygen to the cell wall lignin component, whereas the remainder is esterified to the cell wall hemicelluloses and/or lignin in different plant materials.     

Identification of flavonoids and hydroxycinnamic acids in pak choi varieties (Brassica campestris L. ssp. chinensis var. communis) by HPLC-ESI-MSn and NMR and their quantification by HPLC-DAD

Twenty-eight polyphenols (11 flavonoid derivatives and 17 hydroxycinnamic acid derivatives) were detected in different cultivars of the Chinese cabbage pak choi ( Brassica campestris L. ssp. chinensis var. communis) by HPLC-DAD-ESI-MS(n). Kaempferol was found to be the major flavonoid in pak choi, glycosylated and acylated with different compounds. Smaller amounts of isorhamnetin were also detected. A structural determination was carried out by (1)H and (13)C NMR spectroscopy for the main compound, kaempferol-3-O-hydroxyferuloylsophoroside-7-O-glucoside, for the first time. Hydroxycinnamic acid derivatives were identified as different esters of quinic acid, glycosides, and malic acid. The latter ones are described for the first time in cabbages. The content of polyphenols was determined in 11 cultivars of pak choi, with higher concentrations present in the leaf blade than in the leaf stem. Hydroxycinnamic acid esters, particularly malic acid derivatives, are present in both the leaf blade and leaf stem, whereas flavonoid levels were determined only in the leaf blade.     

Characterization by LC-MS(n) of four new classes of chlorogenic acids in green coffee beans: dimethoxycinnamoylquinic acids, diferuloylquinic acids, caffeoyl-dimethoxycinnamoylquinic acids, and feruloyl-dimethoxycinnamoylquinic acids

LC-MS4 has been used to detect and characterize in green coffee beans 12 chlorogenic acids not previously reported in nature. These comprise three isomeric dimethoxycinnamoylquinic acids (7-9) (Mr 382), three caffeoyl-dimethoxycinnamoylquinic acids (22, 24, and 26) (Mr 544), three diferuloylquinic acids (13-15) (Mr 544), and three feruloyl-dimethoxycinnamoylquinic acids (28, 30, and 32) (Mr 558). Structures have been assigned on the basis of LC-MS4 patterns of fragmentation and relative hydrophobicity and, in the case of the dimethoxycinnamoylquinic acids, by comparison with authentic standards. Several new structure-diagnostic fragmentations have been identified for use with diacyl-chlorogenic acids, for example, m/z 299 and 255 for C4 caffeoyl, m/z 313 and 269 for C4 feruloyl, nearly equal elimination of both cinnamoyl residues for vic-3,4-diacyl, and an increasing ratio of "dehydrated" ions to "non-dehydrated" ions at MS2 with increasing methylation of those cinnamoyl residues. Possible mechanisms have been proposed to account for the fragmentations observed. The mass spectrometric resolution of six isomeric chlorogenic acids (Mr 544) in a crude plant extract by fragment-targeted LC-MS2 and LC-MS3 experiments illustrates the analytical power and advantage of ion trap mass spectroscopy.     

Interactions between montmorillonite and fulvic acid

The isotherms at 20°C for the adsorption of ¹⁴C-labelled fulvic acid from aqueous solutions by montmorillonite containing different exchangeable cations, have been determined. Below a concentration of 0.45 mg/ml and at near neutral pH, all samples give linear isotherms, the slope of which increases in the order Ba²⁺ < Ca²⁺ < Zn²⁺ < La³⁺ < Al³⁺ <Cu²⁺ < Fe³⁺. In the absence of interlayer expansion, the shape of the isotherms is interpreted in terms of solute entry into intercrystalline pores within a clay domain. The affinity of fulvic acid for the clay surface is related to the ionic potential or polarising power of the exchangeable cation. It is inferred that fulvic acid adsorbs by hydrogen bonding between an anionic group of the acid and a water molecule in the primary hydration shell of the saturating cation. Comparison of the data with those for the humic acid extracted from the same organic matter source, indicates that secondary interactions between adsorbed molecules or directly with the montmorillonite surface, contribute to the overall affinity. With samples saturated with Al³⁺, Fe³⁺, and Cu²⁺ ions, part of the adsorbed fulvic acid may also be attached to the clay by a complexation reaction involving the metals as such, or when they exist as polyhydroxy compounds at the mineral surface.     

几种胡敏酸还原容量的表征与比较

还原容量(RC)是衡量胡敏酸(HA)还原特性的重要指标。采用饱和H2振荡法和土壤溶液法对HA分别进行化学和微生物预处理,分别以硝酸铁(Fe(NO3)3)、柠檬酸铁(FeCit)作电子受体,测定了三种HA(上海巨枫SH,天津光复TJ,缙云山JY)的本底还原容量(NRC),化学还原容量(CRC),微生物还原容量(MRC)。对不同电子受体条件下、不同初始状态和不同种类的胡敏酸的RC进行比较。结果表明：三种HA中,以缙云山土壤提取的胡敏酸RC值最高,还原容量最大,分别为20.21?0.26mmolc mol-1C (NRC)、26.02?1.12mmolc mol-1C (CRC)和29.29?1.56mmolc mol-1C (MRC)。两种电子受体中,采用Fe(NO3)3得到的RC明显高于在FeCit条件下。另外,溶液态HA的RC明显高于固态。由此证明胡敏酸还原容量是一个相对量;其容量大小不仅和自身结构、性质有关,也受到HA初始形态和不同电子受体的影响。对比三个还原容量指标发现CRC和MRC显著大于NRC,而CRC和MRC之间无明确大小关系,因此用CRC来表征HA被微生物还原后的还原容量(MRC)还需作进一步验证。     

Sorption of organic acids in acid soils and its implications in the rhizosphere

Organic acids have been implicated in many soil-forming and rhizosphere processes, but their fate in soil is poorly understood. We examined the sorption of four simple short-chain organic acids (citric, oxalic, malic and acetic) in five acid soils and on synthetic iron hydroxide (ferrihydrite). The results for both soils and ferrihydrite indicated that the sorption depended on concentration in the following order of strength: phosphate >> oxalate > citrate > malate >> acetate. The sorption reactions in soil were shown to be little influenced by pH, whereas for ferrihydrite, sorption of all ligands increased strongly with decreasing pH. The sorption of organic anions onto ferrihydrite was influenced to a lesser extent by the presence of metal cations in solution. From the results we calculated that when organic acids enter solution they rapidly become sorbed onto the soil's exchange complex (> 80% within 10 min), and we believe that this sorption will greatly diminish their effectiveness to mobilize nutrients from the rhizosphere.     

Competition for amino acids between wheat roots and rhizosphere microorganisms and the role of amino acids in plant N acquisition

The direct uptake of organic nitrogen compounds from the soil solution by plant roots has been hypothesised to constitute a significant source of N to the plant particularly in N limiting ecosystems. The experiments undertaken here were designed to test whether wheat roots could out-compete the rhizosphere microflora for a pulse addition of organic N in the form of three contrasting amino acids, namely lysine, glycine and glutamate. Amino acids were added at a concentration reflecting reported soil solution concentrations (100 μM) and the uptake into either plant biomass or respiration or microbial biomass and respiration determined over a 24 h chase period. The results showed that the plant roots could only capture on average 6% of the added amino acid with the remainder captured by the microbial biomass. We therefore present direct in vivo evidence to support earlier work which has hypothesised that organic N may be of only limited consequence in high input agricultural systems. We suggest that this is a result of the higher concentrations of NO₃⁻ in agricultural soil solutions, the slow movement of amino acids in soil relative to NO₃⁻, the rapid turnover of amino acids by soil microorganisms, and the poor competitive ability of plant roots to capture amino acids from the soil solution.     

Antifeedant activity of some pentacyclic triterpene acids and their fatty acid ester analogues

The 3-O-fatty acid ester derivatives (C(12)-C(18)) of two pentacyclic triterpenic acids, ursolic acid and oleanolic acid, were synthesized under mild esterification conditions in excellent yields (80-85%) and screened for their antifeedant activity, together with the parent acids, against the agricultural pest tobacco caterpillar larvae (Spodoptera litura F) in a no-choice laboratory study. The Urs-12-ene-28-carboxy-3beta-octadecanoate and olean-12-ene-28-carboxy-3beta-hexadecanoate were found to exhibit exceptionally potent antifeedant activities at 50 microg/cm(2) concentration, even after 48 h.     

Combination reaction between humic acid and calcium ions

In the previous paper (1), liming an acid humus volcanic ash soil resulted in the formation of humic acids combined with calcium, but had no significant effect on acid brown forest soils containing humic acids of a lower degree of humification. Subsequently, the authors examined the humus composition of the soils treated with calcium acetate, and conducted some experiments on the combination reaction between humic acid and calcium ions. The results obtained are presented in this paper.