Comparison of antioxidant activities of different parts from snow chrysanthemum (Coreopsis tinctoria Nutt.) and identification of their natural antioxidants using high performance liquid chromatography coupled with diode array detection and mass spectrometry and 2,2'-azinobis(3-ethylbenzthiazoline-sulfonic acid)diammonium salt-based assay

Snow chrysanthemum (Coreopsis tinctoria Nutt.), a world-widely well-known flower tea material, has attracted more and more attention because of its beneficial health effects such as antioxidant activity and special flavor. In this study, a high performance liquid chromatography coupled with diode array detection and mass spectrometry (HPLC-DAD-MS) and 2,2'-azinobis(3-ethylbenzthiazoline-sulfonic acid)diammonium salt (ABTS) based assay was employed for comparison and identification of antioxidants in different samples of snow chrysanthemum. The results showed that snow chrysanthemum flowers possessed the highest while stems presented the lowest antioxidant capacities. Fourteen detected peaks with antioxidant activity were temporarily identified as 3,4',5,6,7-pentahydroxyflavanone-O-hexoside, chlorogenic acid, 2R-3',4',8-trihydroxyflavanone-7-O-glucoside, flavanomarein, flavanocorepsin, flavanokanin, quercetagitin-7-O-glucoside, 3',5,5',7-tetrahydroxyflavanone-O-hexoside, marein, maritimein, 1,3-dicaffeoylquinic acid, coreopsin, okanin and acetyl-marein by comparing their UV spectra, retention times and MS data with standards or literature data. Antioxidants existed in snow chrysanthemum are quite different from those reported in Chrysanthemum morifolium, a well-known traditional beverage in China, which indicated that snow chrysanthemum may be a promising herbal tea material with obvious antioxidant activity.

Metal Complex Pigment Involved in the Blue Sepal Color Development of Hydrangea

Anthocyanins exhibit various vivid colors from red through purple to blue and are potential sources of food colorants. However, their usage is restricted because of their instability, especially as a blue colorant. The blue sepal color of Hydrangea macrophylla is due to a metal complex named "hydrangea-blue complex" composed of delphinidin 3-O-glucoside, 1, 5-O-caffeoylquinic acid, 2, and/or 5-O-p-coumaroylquinic acid, 3, as copigments, and Al(3+) in aqueous solution at approximately pH 4.0. However, the ratio of each component ins not stoichiometric, but is fluctuates within a certain range. The hydrangea-blue complex exists only in aqueous solution, exhibiting a stable blue color, but attempts at crystallization have failed; therefore, the structure remains obscure. To clarify the basis of the character of the hydrangea-blue pigment and to obtain its structural information, we studied the mixing conditions to reconstruct the same blue color as observed in the sepals. In highly concentrated sodium acetate buffer (6 M, pH 4.0) we could measure (1)H NMR of both the hydrangea-blue complex composed of 1 (5 mM), 2 (10 mM), and Al(3+) (10 mM) and a simple 1-Al(3+) complex. We also recorded the spectra of complexes composed with structurally different anthocyanins and copigments. Comparison of those signals indicated that in the hydrangea-blue complex 1 might be under equilibrium between chelating and nonchelating structures having an interaction with 2.

Chemoreversal Metabolites from the Endophytic Fungus Penicillium citrinum Isolated from a Mangrove Avicennia marina

Two new compounds, named (Z)-7,4'-dimethoxy-6-hydroxyaurone-4-O-β-glucopyranoside (1) and (-)-4-O-(4-O-β-D-glucopyranosylcaffeoyl)quinic acid (2), were isolated from the endophytic fungus Penicillium citrinum of Avicennia marina. Their structures were elucidated on the basis of spectroscopic analysis. Additionally, compound 2 exhibited potent chemoreversal activity, mainly by inhibiting P-glycoprotein efflux pump function.

Parallel reductions in phenolic constituents resulting from the domestication of eggplant

Crop domestication is often accompanied by changes in metabolite compositions that alter traits such as flavor, color, or other beneficial properties. Fruits of eggplants (Solanum melongena L.) and related species are abundant and diverse in pharmacologically interesting phenolic compounds, particularly hydroxycinnamic acid (HCA) conjugates such as the antioxidant caffeoylquinic acids (CQA) and HCA-polyamine amides (HCAA). To understand metabolite variability through the lens of natural and artificial selection, HPLC-DAD was used to generate phenolic profiles for 32 compounds in fruits from 93 accessions representing 9 Solanum species. Profiles were used for identification of species-level and infraspecific chemical patterns across both genetic distance and landscape. Sampling of plant lines included the undomesticated progenitor of eggplant and Asian landraces with a genetic background associated with three Asian regions near proposed separate centers of domestication to test whether chemical changes were convergent despite different origins. Results showed ten compounds were unique to species, and ten other compounds varied significantly in abundance among species. Five CQAs and three HCA-polyamine conjugates were more abundant in wild (undomesticated) versus domesticated eggplant, indicating that artificial selection may have led to reduced phenolic levels. No chemical abundance patterns were associated with site-origin. However, one genetically distinct lineage of geographically-restricted SE Asian eggplants (S. melongena subsp. ovigerum) had a higher HCAA content and diversity than other lineages, which is suggested to be related to artificial selection for small, firm fruit. Overall, patterns show that fruit size, palatability and texture were preferentially selected over health-beneficial phytochemical content during domestication of several nightshade crops.

Chlorogenic acid stability in pressurized liquid extraction conditions

Chlorogenic acids (CQAs) are phenolic compounds naturally occurring in all higher plants. They are potentially useful in pharmaceuticals, foodstuffs, food additives, and cosmetics due to their recently suggested biomedical activity. Hence, research interest in CQA properties, their isomers, and natural occurrence has been growing. Pressurized liquid extraction (PLE) is regarded as an effective and quick sample preparation method in plant analysis. The short time of PLE decreases the risk of chemical degradation of extracted compounds, thus increasing the attractiveness of its application. However, PLE applied for plant sample preparation is not free from limitations. We found that trans-5-O-caffeoylquinic acid (trans-5-CQA), the main CQA isomer, isomerizes to 3- and 4-O-caffeoylquinic acids and undergoes transesterification, hydrolysis, and reaction with water even in rapid PLE. Moreover, the number and concentration of trans-5-CQA derivatives formed in PLE strongly depends on extractant composition, its pH, and extraction time and temperature. It was not possible to find the PLE conditions in which the transformation process of trans-5-CQA would be eliminated.

Effect of Processing on the Traditional Chinese Herbal Medicine Flos Lonicerae: An NMR-based Chemometric Approach

The processing of medicinal materials, known as Pao Zhi in traditional Chinese medicine, is a unique part of traditional Chinese medicine and has been widely used for the preparation of Chinese materia medica. It is believed that processing can alter the properties and functions of remedies, increase medical potency, and reduce toxicity and side effects. Both processed and unprocessed Flos Lonicerae (flowers of Lonicera japonica) are important drug ingredients in traditional Chinese medicine. To gain insights on the effect of processing factors (heating temperature and duration) on the change of chemical composition, nuclear magnetic resonance combined with chemometric analysis was applied to investigate the processing of F. Lonicerae. Nuclear magnetic resonance spectral data were analyzed by means of a heat map and principal components analysis. The results indicated that the composition changed significantly, particularly when processing at the higher temperature (210 °C). Five chemical components, viz. 3,4-dicaffeoylquinic acid, 4,5-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid, chlorogenic acid, and myo-inositol, whose concentration changed significantly during the processing, were isolated and identified. The patterns for the concentration change observed from nuclear magnetic resonance analysis during the processing were confirmed and quantitatively determined by ultrahigh-performance liquid chromatography analysis. The study demonstrated that a nuclear magnetic resonance-based chemometric approach could be a promising tool for investigation of the processing of herbal medicines in traditional Chinese medicine.

Rapid Fingerprint Analysis of Plant Extracts for Ellagitannins, Gallic Acid, and Quinic Acid Derivatives and Quercetin-, Kaempferol- and Myricetin-Based Flavonol Glycosides by UPLC-QqQ-MS/MS

This paper describes the development of a rapid method with ultraperformance liquid chromatography-triple-quadrupole mass spectrometry that can specifically measure group-specific fingerprints from plant extracts for the following polyphenol groups: (1) ellagitannins, (2) gallic acid derivatives, (3) quinic acid derivatives, (4) quercetin-based flavonol glycosides, (5) kaempferol-based flavonol glycosides, and (6) myricetin-based flavonol glycosides. In addition, the method records simultaneously diode array and full scan mass spectrometry data that can be used to later characterize and quantify the main individual polyphenols if necessary. All of this is achieved within the 10 min period of analysis, which makes the presented method a significant addition to the chemistry tools currently available for the rapid analysis of complex polyphenol mixtures from plant extracts.

Inhibitory activities of caffeoylquinic acid derivatives from Ilex kudingcha C.J. Tseng on α-glucosidase from Saccharomyces cerevisiae

Polyphenols and caffeoylquinic acid (CQA) derivatives (3-CQA, 4-CQA, 5-CQA, 3,4-diCQA, 3,5-diCQA, and 4,5-diCQA) were prepared from Ilex kudingcha C.J. Tseng, and their effects and mechanisms on the activities of α-glucosidase from Saccharomyces cerevisiae were investigated in the present study. As results, the IC50 values for CQA derivatives were 0.16-0.39 mg/mL, and the inhibition mode of CQA derivatives was noncompetitive. On the basis of fluorescence spectroscopy and circular dichroism spectroscopy data, the binding constants and number of binding sites were calculated to be 10(6)-10(8) M(-1) and 1.42-1.87, respectively. CQA derivatives could bind to the enzyme mainly through hydrophobic interaction, altering the microenvironment and molecular conformation of the enzyme, thus decreasing the catalytic activity. To the authors' knowledge, this is the first report on α-glucosidase inhibitory mechanism by CQA derivatives from I. kudingcha, and the findings suggest a potential use of kudingcha as functional foods for the prevention and treatment of diabetes and related symptoms.

[Pandanus tectorius derived caffeoylquinic acids inhibit lipid accumulation in HepG2 hepatoma cells through regulation of gene expression involved in lipid metabolism]

The fruit of Pandanus tectorius (PTF) has a long history of use as a folk medicine to treat hyperlipidemia in Hainan province, South China. Our previous studies have shown that the n-butanol extract of PTF is rich in caffeoylquinic acids and has an adequate therapeutic effect on dyslipidemic animals induced by high-fat diet. In this work, seven caffeoylquinic acids isolated from PTF were screened for the lipid-lowering activity in HepG2 hepatoma cells. Oil-Red O staining, microscopy and intracellular triglyceride (TG) and total cholesterol (TC) quantification showed that 3-O-caffeoylquinic acid (3-CQA), 3, 5-di-O-caffeoylquinic acid (3,5-CQA), and 3,4,5-tri-O-caffeoylquinic acid (3,4,5-CQA) significantly inhibited lipid accumulation induced by oleic acid and decreased intracellular levels of TC and TG in a dose-dependent manner. These three caffeoylquinic acids showed no significant cytotoxicity at concentrations of 1 -50 μmol x L(-1) as determined by MTT assay. Realtime quantitative PCR revealed that 3-CQA and 3, 5-CQA significantly increased the expression of lipid oxidation-related genes PPARα, CPT-1 and ACOX1 while 3-CQA, 3, 5-CQA and 3,4,5-CQA decreased the expression of lipogenic genes SREBP-1c, SREBP-2, HMGR, ACC, FAS. Overall, 3-CQA, 3, 5-CQA and 3, 4, 5-CQA may be the principal hypolipidemic components in PTF which can decrease intracellular lipid accumulation through up-regulating the expression of lipid oxidative genes and down-regulating the expression of lipogenic genes.

Identification and characterization of chlorogenic acids, chlorogenic acid glycosides and flavonoids from Lonicera henryi L. (Caprifoliaceae) leaves by LC-MSn

The chlorogenic acids, chlorogenic acid glycosides and flavonoids of the leaves of Lonicera henryi L. (Caprifoliaceae) were investigated qualitatively by liquid chromatography tandem mass spectrometry. Thirty-one chlorogenic acids and their glycosides were detected and characterized to their regioisomeric level on the basis of their unique fragmentation pattern in the negative ion mode tandem MS spectra. All of them were extracted for the first time from this source and thirteen of them were not reported previously in nature. For the positive identification of chlorogenic acid glycosides by LC-MS(n), multiple reaction monitoring and targeted MS(n) experiments were performed. We have developed an LC-MS(n) method for the systematic identification of chlorogenic acid glycosides and were also able to discriminate between chlorogenic acids and their isobaric glycosides. It was also possible to discriminate between 5-O-(3'-O-caffeoyl glucosyl)quinic acid and 5-O-(4'-O-caffeoyl glucosyl)quinic acid by LC-MS(n). This method can be applied for the rapid and positive identification of chlorogenic acids and their glycosides in plant materials, food and beverages.

[Chemical constituents from Artemisia annua]

OBJECTIVE

To investigate the chemical constituents of dried whole plants of Artemisia annua.

METHOD

The chemical constituents were isolated by repeated silica gel chromatography, medium pressure column chromatography, and semi-preparative HPLC, and their structures were elucidated by spectroscopic analyses and comparison of NMR data with those reported in literature.

RESULT

15 compounds were isolated and identified to be 5-O-[(E)-Caffeoyl] quinic acid(l), 1,3-di-O-caffeoylquinic acid(2), 4 5-di-O-caffeoylquinic acid(3), 3, 5-di-O-caffeoylquinic acid (4), 3, 4-di-O-caffeoylquinic acid (5), methyl-3,4-di-O-caffeoylquinic acid(6), methyl-3,5-di-O-caffeoylquinic acid(7), 3,6'-O-diferuloylsucrose(8), 5'-β-D-glucopyranosyloxyjasmonic acid(9), Scopoletin(10), scoparone (11), 4-O-β-D-glucopyranosyl-2-hydroxyl-6-methoxyacetophenone (12), chrysosplenol D (13), casticin (14), chrysosplenetin(15).

CONCLUSION

Compounds 2, 6, 8 and 9 are obtained from the Artemisia genus for the first time. Compounds 7 and 15 are obtained from this plant for the first time.

Dual catalytic activity of hydroxycinnamoyl-coenzyme A quinate transferase from tomato allows it to moonlight in the synthesis of both mono- and dicaffeoylquinic acids

Tomato (Solanum lycopersicum), like other Solanaceous species, accumulates high levels of antioxidant caffeoylquinic acids, which are strong bioactive molecules and protect plants against biotic and abiotic stresses. Among these compounds, the monocaffeoylquinic acids (e.g. chlorogenic acid [CGA]) and the dicaffeoylquinic acids (diCQAs) have been found to possess marked antioxidative properties. Thus, they are of therapeutic interest both as phytonutrients in foods and as pharmaceuticals. Strategies to increase diCQA content in plants have been hampered by the modest understanding of their biosynthesis and whether the same pathway exists in different plant species. Incubation of CGA with crude extracts of tomato fruits led to the formation of two new products, which were identified by liquid chromatography-mass spectrometry as diCQAs. This chlorogenate:chlorogenate transferase activity was partially purified from ripe fruit. The final protein fraction resulted in 388-fold enrichment of activity and was subjected to trypsin digestion and mass spectrometric sequencing: a hydroxycinnamoyl-Coenzyme A:quinate hydroxycinnamoyl transferase (HQT) was selected as a candidate protein. Assay of recombinant HQT protein expressed in Escherichia coli confirmed its ability to synthesize diCQAs in vitro. This second activity (chlorogenate:chlorogenate transferase) of HQT had a low pH optimum and a high Km for its substrate, CGA. High concentrations of CGA and relatively low pH occur in the vacuoles of plant cells. Transient assays demonstrated that tomato HQT localizes to the vacuole as well as to the cytoplasm of plant cells, supporting the idea that in this species, the enzyme catalyzes different reactions in two subcellular compartments.

Developmental changes in leaf phenolics composition from three artichoke cvs. (Cynara scolymus) as determined via UHPLC-MS and chemometrics

The metabolomic differences in phenolics from leaves derived from 3 artichoke cultivars (Cynara scolymus): American Green Globe, French Hyrious and Egyptian Baladi, collected at different developmental stages, were assessed using UHPLC-MS coupled to chemometrics. Ontogenic changes were considered as leaves were collected at four different time intervals and positions (top and basal) during artichoke development. Unsupervised principal component analysis (PCA) and supervised orthogonal projection to latent structures-discriminant analysis (O2PLS-DA) were used for comparing and classification of samples harvested from different cultivars at different time points and positions. A clear separation among the three investigated cultivars was revealed, with the American Green Globe samples found most enriched in caffeic acid conjugates and flavonoids vs. other cultivars. Furthermore, these metabolites also showed a marked effect on the discrimination between leaf samples from cultivars harvested at different positions, regardless of the plant age. Metabolite absolute quantifications further confirmed that discrimination was mostly influenced by phenolic compounds, namely caffeoylquinic acids and flavonoids. This study demonstrates an effect of artichoke leaf position, regardless of plant age, on its secondary metabolites composition. To the best of our knowledge, this is the first report for compositional differences among artichoke leaves, based on their positions, via a metabolomic approach and suggesting that top positioned artichoke leaves present a better source of caffeoylquinic acids, compared to basal ones.

Transformation of 5-O-caffeoylquinic acid in blueberries during high-temperature processing

Chlorogenic acid (CQA), an ester of caffeic with quinic acid, is a natural compound found in a wide array of plants. Although coffee beans are most frequently mentioned as plant products remarkably rich in CQAs, their significant amounts can also be found in many berries, for example, blueberries. This paper shows and discusses the thermal stability of the main CQA representative, that is, 5-O-caffeoylquinic acid (5-CQA), during high-temperature processing of blueberries (as in the production of blueberry foods) in systems containing sucrose in low and high concentration. It has been found that up to 11 components (5-CQA derivatives and its reaction product with water) can be formed from 5-CQA during the processing of blueberries. Their formation speed depends on the sucrose concentration in the processed system, which has been confirmed in the artificial system composed of 5-CQA water solution containing different amounts of the sugar.

Photo-cross-linked poly(thioether-co-carbonate) networks derived from the natural product quinic acid

Polycarbonate networks derived from the natural product quinic acid that can potentially return to their natural building blocks upon hydrolytic degradation are described herein. Solvent-free thiol-ene chemistry was utilized in the copolymerization of tris(alloc)quinic acid and a variety of multifunctional thiol monomers to obtain poly(thioether-co-carbonate) networks with a wide range of achievable thermomechanical properties including glass transition temperatures from -18 to +65 °C and rubbery moduli from 3.8 to 20 MPa. The network containing 1,2-ethanedithiol expressed an average toughness at 25 and 63 °C of 1.08 and 2.35 MJ/m(3), respectively, and an order-of-magnitude increase in the average toughness at 37 °C of 15.56 MJ/m(3).

Antioxidant, 5-lipoxygenase inhibitory and cytotoxic activities of compounds isolated from the Ferula lutea flowers

A phytochemical investigation of the Ferula lutea (Poir.) Maire flowers has led to the isolation of a new compound, (E)-5-ethylidenefuran-2(5H)-one-5-O-β-d-glucopyranoside (1), designated ferunide, 4-hydroxy-3-methylbut-2-enoic acid (2), reported for the first time as a natural product, together with nine known compounds, verbenone-5-O-β-d-glucopyranoside (3), 5-O-caffeoylquinic acid (4), methyl caffeate (5), methyl 3,5-O-dicaffeoylquinate (6), 3,5-O-dicaffeoylquinic acid (7), isorhamnetin-3-O-α-l-rhamnopyranosyl(1→6)-β-d-glucopyranoside, narcissin (8), (−)-marmesin (9), isoimperatorin (10) and 2,3,6-trimethylbenzaldehyde (11). Compounds 3–10 were identified for the first time in Ferula genus. Their structures were elucidated by spectroscopic methods, including 1D and 2D NMR experiments, mass spectroscopy and X-ray diffraction analysis (compound 2), as well as by comparison with literature data. The antioxidant, anti-inflammatory and cytotoxic activities of isolated compounds were evaluated. Results showed that compound 7 exhibited the highest antioxidant activity with IC₅₀ values of 18 ± 0.5 µmol/L and 19.7 ± 0.7 µmol/L by DPPH radical and ABTS radical cation, respectively. The compound 6 exhibited the highest anti-inflammatory activity with an IC₅₀ value of 5.3 ± 0.1 µmol/L against 5-lipoxygenase. In addition, compound 5 was found to be the most cytotoxic, with IC₅₀ values of 22.5 ± 2.4 µmol/L, 17.8 ± 1.1 µmol/L and 25 ± 1.1 µmol/L against the HCT-116, IGROV-1 and OVCAR-3 cell lines, respectively.

Influence of sulfur fumigation on the chemical constituents and antioxidant activity of buds of Lonicera japonica

Lonicera japonica flos is widely used as a pharmaceutical resource and a commonly-employed ingredient in healthy food, soft beverages and cosmetics in China. Sometimes, sulfur fumigation is used during post-harvest handling. In this study, a comprehensive comparison of the chemical profile between sun-dried and sulfur-fumigated samples was conducted by HPLC fingerprints and simultaneous quantification of nine constituents, including secologanic acid, along with another eight usually-analyzed markers. Secologanic acid was destroyed, and its sulfonates were generated, whereas caffeoylquinic acids were protected from being oxidized. The residual sulfur dioxide in sulfur-fumigated samples was significantly higher than that in sun-dried samples, which might increase the potential incidence of toxicity to humans. Meanwhile, compared with sun-dried samples, sulfur-fumigated samples have significantly stronger antioxidant activity, which could be attributed to the joint effect of protected phenolic acids and flavonoids, as well as newly-generated iridoid sulfonates.

Investigation of acyl migration in mono- and dicaffeoylquinic acids under aqueous basic, aqueous acidic, and dry roasting conditions

Acyl migration in chlorogenic acids describes the process of migration of cinnamoyl moieties from one quinic acid alcohol group to another, thus interconverting chlorogenic acid regioisomers. It therefore constitutes a special case of transesterification reaction. Acyl migration constitutes an important reaction pathway in both coffee roasting and brewing, altering the structure of chlorogenic acid initially present in the green coffee bean. In this contribution we describe detailed and comprehensive mechanistic studies comparing inter- and intramolecular acyl migration involving the seven most common chlorogenic acids in coffee. We employe aqueous acidic and basic conditions mimicking the brewing of coffee along with dry roasting conditions. We show that under aqueous basic conditions intramolecular acyl migration is fully reversible with basic hydrolysis competing with acyl migration. 3-Caffeoylquinic acid was shown to be most labile to basic hydrolysis. We additionally show that the acyl migration process is strongly pH dependent with increased transesterification taking place at basic pH. Under dry roasting conditions acyl migration competes with dehydration to form lactones. We argue that acyl migration precedes lactonization, with 3-caffeoylquinic acid lactone being the predominant product.

[Caffeoylquinic acid derivatives from stems of Akebia trifoliata]

OBJECTIVE

To study the chemical constituents from Akebia trifoliata stems.

METHODS

The compounds were isolated and purified by column chromatography, and their structures were determined through spectroscopic techniques and physicochemical properties.

RESULTS

Six compounds were isolated from the stems of Akebia trifolita and identified as cryptochlorogenic acid methyl ester (1), neochlorogenic acid methyl ester (2), chlorogenic acid methyl ester (3), methyl 3,5-di-O-caffeoyl quinate (4), methyl 3,4-di-O-caffeoyl quinate (5) and methyl 4,5-di-O-caffeoyl quinate (6).

CONCLUSION

All compounds are isolated from Akebia genus for the first time. Compounds 1,5 and 6 demonstrate obvious inhibitory activities against α-glucosidase.

Enzyme-substrate complexes of the quinate/shikimate dehydrogenase from Corynebacterium glutamicum enable new insights in substrate and cofactor binding, specificity, and discrimination

Quinate dehydrogenase (QDH) catalyzes the reversible oxidation of quinate to 3-dehydroquinate by nicotineamide adenine dinucleotide (NADH) and is involved in the catabolic quinate metabolism required for the degradation of lignin. The enzyme is a member of the family of shikimate/quinate dehydrogenases (SDH/QDH) occurring in bacteria and plants. We characterized the dual-substrate quinate/shikimate dehydrogenase (QSDH) from Corynebacterium glutamicum (CglQSDH) kinetically and revealed a clear substrate preference of CglQSDH for quinate compared with shikimate both at the pH optimum and in a physiological pH range, which is a remarkable contrast to closely related SDH/QDH enzymes. With respect to the cosubstrate, CglQSDH is strictly NAD(H) dependent. These substrate and cosubstrate profiles correlate well with the details of three atomic resolution crystal structures of CglQSDH in different functional states we report here: with bound NAD+ (binary complex) and as ternary complexes with NADH plus either shikimate or quinate. The CglQSDH-NADH-quinate structure is the first complex structure of any member of the SDH/QDH family with quinate. Based on this novel structural information and systematic sequence and structure comparisons with closely related enzymes, we can explain the strict NAD(H) dependency of CglQSDH as well as its discrimination between shikimate and quinate.

Structure- and dose-absorption relationships of coffee polyphenols

Chlorogenic acids (CGAs) from coffee have biological effects related to human health. Thus, specific data on their bioavailability in the upper gastrointestinal tract are of high interest, since some molecules are absorbed here and so are not metabolized by colonic microflora. Up to now, no data on structure-absorption relationships for CGAs have been published, despite this being the most consumed group of polyphenols in the western diet. To address this gap, we performed ex vivo absorption experiments with pig jejunal mucosa using the Ussing chamber model (a model simulating the mucosa and its luminal/apical side). The main coffee polyphenols, caffeoylquinic acid (CQA), feruloylquinic acid (FQA), caffeic acid (CA), dicaffeoylquinic acid (diCQA), and D-(-)-quinic acid (QA), were incubated in individual experiments equivalent to gut lumen physiologically achievable concentrations (0.2-3.5 mM). Identification and quantification were performed with HPLC-diode array detection and HPLC-MS/MS. Additionally, the presence of ABC-efflux transporters was determined by Western blot analysis. The percentages of initially applied CGAs that were absorbed through the jejunal pig mucosa were, in increasing order: diCQA, trace; CQA, ≈ 1%; CA, ≈ 1.5%; FQA, ≈ 2%; and QA, ≈ 4%. No differences were observed within the CGA subgroups. Dose-absorption experiments with 5-CQA suggested a passive diffusion (nonsaturable absorption and a linear dose-flux relationship) and its secretion was affected by NaN3 , indicating an active efflux. The ABC-efflux transporters MDR 1 and MRP 2 were identified in pig jejunal mucosa for the first time. We conclude that active efflux plays a significant role in CGA bioavailability and, further, that the mechanism of CGA absorption in the jejunum is governed by their physicochemical properties.

Quantitative studies on roast kinetics for bioactives in coffee

Quantitative analysis of the bioactives trigonelline (1), N-methylpyridinium (2), caffeine (3), and caffeoylquinic acids (4) in a large set of roasted Arabica (total sample size n = 113) and Robusta coffees (total sample size n = 38) revealed that the concentrations of 1 and 4 significantly correlated with the roasting color (P < 0.001, two tailed), whereas that of 2 significantly correlated inversely with the color (P < 0.001, two tailed). As dark-roasted coffees were rich in N-methylpyridinium whereas light-roasted coffees were rich in trigonelline and caffeoylquinic acids, manufacturing of roast coffees rich in all four bioactives would therefore necessitate blending of two or even more coffees of different roasting colors. Additional experiments on the migration rates during coffee brewing showed that all four bioactives were nearly quantitatively extracted in the brew (>90%) when a water volume/coffee powder ratio of >16 was used.

Impact of chemical changes on the sensory characteristics of coffee beans during storage

Sensory changes during the storage of coffee beans occur mainly due to lipid oxidation and are responsible for the loss of commercial value. This work aimed to verify how sensory changes of natural coffee and pulped natural coffee are related to the oxidative processes during 15 months of storage. During this period, changes in the content of free fatty acids (1.4-3.8 mg/g oil), TBARS values (8.8-10.2 nmol MDA/g), and carbonyl groups (2.6-3.5 nmol/mg of protein) occurred. The intensity of "rested coffee flavour" in the coffee brew increased (2.1-6.7) and 5-caffeoylquinic acid concentration decreased (5.2-4.6g/100g). Losses were also observed in seed viability, colour of the beans and cellular structure. All the results of the chemical analyses are coherent with the oxidative process that occurred in the grains during storage. Therefore, oxidation would be also responsible for the loss of cellular structure, seed viability and sensory changes.

Acylated sucroses and acylated quinic acids analogs from the flower buds of Prunus mume and their inhibitory effect on melanogenesis

The methanolic extract from the flower buds of Prunus mume, cultivated in Zhejiang Province, China, showed an inhibitory effect on melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells. From the methanolic extract, five acylated sucroses, mumeoses A-E, and three acylated quinic acid analogs, 5-O-(E)-p-coumaroylquinic acid ethyl ester, and mumeic acid-A and its methyl ester, were isolated together with 13 known compounds. The chemical structures of the compounds were elucidated on the basis of chemical and physicochemical evidence. Inhibitory effects of the isolated compounds on melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells were also investigated. Acylated quinic acid analogs substantially inhibited melanogenesis. In particular, 5-O-(E)-feruloylquinic acid methyl ester exhibited a potent inhibitory effect [inhibition (%): 21.5±1.0 (P<0.01) at 0.1 μM]. Moreover, its biological effect was much stronger than that of the reference compound, arbutin [inhibition (%): 10.6±0.6 (P<0.01) at 10 μM]. Interestingly, the obtained acylated quinic acid analogs displaying melanogenesis inhibitory activity showed no cytotoxicity [cell viability >97% at 10 μM]. It is concluded that acylated quinic acid analogs are promising therapeutic agents for the treatment of skin disorders.

Chemical constituents from Tribulus terrestris and screening of their antioxidant activity

Two oligosaccharides (1,2) and a stereoisomer of di-p-coumaroylquinic acid (3) were isolated from the aerial parts of Tribulus terrestris along with five known compounds (4-8). The structures of the compounds were established as O-β-D-fructofuranosyl-(2→6)-α-D-glucopyranosyl-(1→6)-β-D-fructofuranosyl-(2→6)-β-D-fructofuranosyl-(2→1)-α-D-glucopyranosyl-(6→2)-β-D-fructofuranoside (1), O-α-D-glucopyranosyl-(1→4)-α-D-glucopyranosyl-(1→4)-α-D-glucopyranosyl-(1→2)-β-D-fructofuranoside (2), 4,5-di-p-cis-coumaroylquinic acid (3) by different spectroscopic methods including 1D NMR ((1)H, (13)C and DEPT) and 2D NMR (COSY, TOCSY, HMQC and HMBC) experiments as well as ESI-MS analysis. This is the first report for the complete NMR spectral data of the known 4,5-di-p-trans-coumaroylquinic acid (4). The antioxidant activity represented as DPPH free radical scavenging activity was investigated revealing that the di-p-coumaroylquinic acid derivatives possess potent antioxidant activity so considered the major constituents contributing to the antioxidant effect of the plant.