Hydroxycinnamic Acid Conjugates Research Articles

Characterization of phytochemicals from twisted-leaf garlic (Allium obliquum L.) using liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry

IntroductionTwisted-leaf garlic (Allium obliquum L.) is a wild Allium species, which is traditionally used as aroma plant for culinary purposes due to its unique, garlic-like flavor. It represents an interesting candidate for domestication, breeding and cultivation.ObjectivesThe objective of this work was to explore and comprehensively characterize polar and semi-polar phytochemicals accumulating in leaves and bulbs of A. obliquum.MethodPlant material obtained from a multiyear field trial was analyzed using a metabolite profiling workflow based on ultra-high performance liquid chromatography-coupled electrospray ionization quadrupole time-of-flight mass spectrometry (UHPLC/ESI-QTOFMS) and two chromatographic methods. For annotation of metabolites, tandem mass spectrometry experiments were carried out and the resulting accurate-mass collision-induced dissociation (CID) mass spectra interpreted. Onion and garlic bulb extracts were used as reference samples.ResultsImportant metabolite classes influencing nutritional, sensory and technological properties were detected and structurally characterized including fructooligosaccharides with a degree of polymerization of 3–5, S-alk(en)ylcysteine sulfoxides and other S-substituted cysteine conjugates, flavonoids including O- and C-glycosylated flavones as well as O-glycosylated flavonols, steroidal saponins, hydroxycinnamic acid conjugates, phenylethanoids and free sphingoid bases. In addition, quantitative data for non-structural carbohydrates, S-alk(en)ylcysteine sulfoxides and flavonoids are provided.ConclusionThe compiled analytical data including CID mass spectra of more than 160 annotated metabolites provide for the first time a phytochemical inventory of A. obliquum and lay the foundation for its further use as aroma plant in food industry.

Chitosan–Hydroxycinnamic Acid Conjugates: Synthesis, Physicochemical Characteristics, and Estimation of Their Influence on Productivity and Quality of the Radish

Chitosan–Hydroxycinnamic Acid Conjugates: Synthesis, Physicochemical Characteristics, and Estimation of Their Influence on Productivity and Quality of the Radish

Phenolic Metabolites in the Urine and Plasma of Healthy Men After Acute Intake of Purple Potato Extract Rich in Methoxysubstituted Monoacylated Anthocyanins

Structurally stable acylated anthocyanins have potential in various food applications but the effects of acylation and methoxysubstitution on anthocyanin metabolism are poorly understood. This is the first study thoroughly investigating phenolic metabolites, their time-wise changes, and pharmacokinetics following an acute intake of methoxysubstituted monoacylated anthocyanins. Healthy male volunteers (n = 17) consumed a yellow potato meal with and without purple potato extract rich in acylated anthocyanins (152mg) and hydroxycinnamic acid conjugates (140mg). Ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) is used for identification and quantification of metabolites from serially collected urine and plasma. While the parent anthocyanins are not detected, 28 phenolic metabolites from urine and 14 from plasma are quantified, including hydroxybenzoic and hydroxycinnamic acids and protocatechuic acid sulfates and glucuronides; three (catechol, gallic acid-4-O-glucuronide, and 2-methoxybenzoic acid) are detected for the first time after anthocyanin-rich food. Urinary hippuric acid is the most abundant with an increase of 139µM mM-1 creatinine after the treatment. A large additional set of tentatively identified phenolic metabolites are detected. Late urinary peak time values suggest colonic degradation. Acylated anthocyanins are more bioavailable than earlier reported after extensive degradation in human and/or colonial metabolism to phenolic metabolites, which may be further conjugated and demethylated.

The nature of the progression of drought stress drives differential metabolomic responses in Populus deltoides.

The use of woody crops for Quad-level (approx. 1 × 1018 J) energy production will require marginal agricultural lands that experience recurrent periods of water stress. Populus species have the capacity to increase dehydration tolerance by lowering osmotic potential via osmotic adjustment. The aim of this study was to investigate how the inherent genetic potential of a Populus clone to respond to drought interacts with the nature of the drought to determine the degree of biochemical response. A greenhouse drought stress study was conducted on Populus deltoides 'WV94' and the resulting metabolite profiles of leaves were determined by gas chromatography-mass spectrometry following trimethylsilylation for plants subjected to cyclic mild (-0.5 MPa pre-dawn leaf water potential) drought vs. cyclic severe (-1.26 MPa) drought in contrast to well-watered controls (-0.1 MPa) after two or four drought cycles, and in contrast to plants subjected to acute drought, where plants were desiccated for up to 8 d. The nature of drought (cyclic vs. acute), frequency of drought (number of cycles) and the severity of drought (mild vs. severe) all dictated the degree of osmotic adjustment and the nature of the organic solutes that accumulated. Whereas cyclic drought induced the largest responses in primary metabolism (soluble sugars, organic acids and amino acids), acute onset of prolonged drought induced the greatest osmotic adjustment and largest responses in secondary metabolism, especially populosides (hydroxycinnamic acid conjugates of salicin). The differential adaptive metabolite responses in cyclic vs. acute drought suggest that stress acclimation occurs via primary metabolism in response to cyclic drought, whereas expanded metabolic plasticity occurs via secondary metabolism following severe, acute drought. The shift in carbon partitioning to aromatic metabolism with the production of a diverse suite of higher order salicylates lowers osmotic potential and increases the probability of post-stress recovery.

Characterization of polyphenols in apricot and peach purees by UHPLC coupled to HRMS Q-Exactive(™) mass spectrometer: an approach in the identification of adulterations.

The genuineness of fruit juices and purees is regulated by guidelines of European Fruit Juice Association. Nevertheless, the addition of peach puree to apricot puree is considered the most common adulteration, very difficult to discover. In this study, the composition in free and conjugated polyphenols of apricot and peach purees was performed by target and untarget approaches with Q-Exactive(™) quadrupole-Orbitrap mass spectrometer. Apricot purees showed a higher polyphenol content than those of peaches. Between target coumpounds, chlorogenic acid, rutin, catechin and smaller quantities of hyperoside and kaempferol-3-rutinoside were found in both purees. Apricot puree was also found to contain epicatechin and procianidin B2, absent in peach puree. Peach puree was found to contain small amounts of kaempferol-3-glucoside, absent in apricot. In order to identify untarget polyphenols, data obtained by ultra-high pressure liquid chromatography tandem mass spectrometry analysis were processed with Thermo Scientific automated label-free differential expression software (sieve(™) 2.1 software). Three hydroxycinnamic acid conjugates and a procyanidin were identified and confirmed by tandem mass spectrometry spectra. Some compounds of interest found from differential analysis had a putative identification, while others remained unidentified. The high-resolution mass spectrometry approach using Q-Exactive(™) quadrupole-Orbitrap mass spectrometer could be an important and powerful tool for determination of new biomarkers in fruits and vegetables. Copyright © 2016 John Wiley & Sons, Ltd.

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.

Genotype × environment interactions in eggplant for fruit phenolic acid content

Eggplant fruit are a rich source of phenolic acids that influence fruit culinary quality and antioxidant content. We evaluated the influence of production environments and stability of diverse genotypes across environments for eggplant fruit phenolic acid content. Ten Solanum melongena accessions consisting of five F1 hybrid cultivars, three open-pollinated cultivars and two land race accessions, plus one S. macrocarpon and one S. aethiopicum accession, were grown at two locations under greenhouse and open field environments. Twenty phenolic acid conjugates were identified in fruit flesh and assigned to six classes that included hydroxycinnamic acid amides, caffeoylquinic acid esters, hydroxycinnamoylquinic acid esters, malonylcaffeoylquinic acid esters, di-hydroxycinnamoylquinic acid esters, and other hydroxycinnamic acid conjugates. There were significant differences among accessions for total phenolic acid conjugate content and for all six classes. There were no significant differences detected among the environments for any of the variables. However, the environment × accession interaction was highly significant for all phenolic acid classes. Broad-sense heritability estimates for all six phenolic acid classes were high, ranging from 0.64 to 0.96. Stability analysis demonstrated widespread instability for phenolic acid content across environments. Stability of the predominant caffeoylquinic acid esters class positively influenced stability of total phenolic acid content for some but not all genotypes. High heritability, coupled with highly significant genotype × environment interactions suggests that stability estimates may improve the efficiency of breeding new genotypes with predictable performance across environments.

Respiratory Behavior and Preservation of Mana Cubiu Stored at Different Temperatures of Refrigeration

Mana-cubiu (Solanum sessiliflorum Dunal), also known as cocona, mana, and tomate de indio, is a tropical shrub that produces an exotic fruit that is desirable due to its pleasant flavor and aroma. It used in popular medicine to reduce cholesterol, uric acid and glucose in the blood. The major chemical components in the dried fruit are citric acid (14% of the dry weight) and carbohydrates (32% of the dry weight), but also include 5- caffeoylquinic acid as the major phenolic compound, as well as β-carotene (7.15 μg/g dry weight), lutein (2.41 μg/g dry weight) and spermidine hydroxycinnamic acid conjugates. The respiratory behavior, weight loss and firmness of fruits from maná cubiu (Solanum sessiliflorum) that were stored refrigerated at 6, 8, 10 and 24 °C were evaluated by the liberation of CO2 and their weights. Based on weight loss, storage at room temperature produced inferior quality after 8 days. At 6 and 8 °C the durability was 12 days. At 10 °C, there was less weight loss and better visual appearance. So, the best temperature for storage was found to be 10 °C. Keywords: Mana-cubiu, post-harvest, respiratory activity, Solanum sessiflorum Dunal, weight loss.

The roles of polyamines during the lifespan of plants: from development to stress

Compelling evidence indicates that free polyamines (PAs) (mainly putrescine, spermidine, spermine, and its isomer thermospermine), some PA conjugates to hydroxycinnamic acids, and the products of PA oxidation (hydrogen peroxide and γ-aminobutyric acid) are required for different processes in plant development and participate in abiotic and biotic stress responses. A tight regulation of PA homeostasis is required, since depletion or overaccumulation of PAs can be detrimental for cell viability in many organisms. In plants, homeostasis is achieved by modulation of PA biosynthesis, conjugation, catabolism, and transport. However, recent data indicate that such mechanisms are not mere modulators of PA pools but actively participate in PA functions. Examples are found in the spermidine-dependent eiF5A hypusination required for cell division, PA hydroxycinnamic acid conjugates required for pollen development, and the involvement of thermospermine in cell specification. Recent advances also point to implications of PA transport in stress tolerance, PA-dependent transcriptional and translational modulation of genes and transcripts, and posttranslational modifications of proteins. Overall, the molecular mechanisms identified suggest that PAs are intricately coordinated and/or mediate different stress and developmental pathways during the lifespan of plants.

Chitosan–hydroxycinnamic acid conjugates: Preparation, antioxidant and antimicrobial activity

In this study, the antioxidant and antimicrobial activities of chitosan–caffeic acid, chitosan–ferulic acid, and chitosan–sinapic acid conjugates with different grafting ratios were investigated. The synthesized chitosan–hydroxycinnamic acid conjugates were verified by performing 1H NMR and differential scanning calorimetry analysis. The antioxidant activities of the conjugates were increased compared to the unmodified chitosan, by 1.79-fold to 5.05-fold (2,2-diphenyl-1-picrylhydrazyl scavenging assay), 2.44-fold to 4.12-fold (hydrogen peroxide scavenging assay), 1.34-fold to 3.35-fold (ABTS+ radical scavenging assay), and also exhibited an increased reducing power. The conjugates also showed excellent lipid peroxidation inhibition abilities in a linoleic acid emulsion system. The conjugates exhibited antimicrobial activity against 15 clinical isolates, two standard methicillin-resistant Staphylococcus aureus (MRSA) and three standard methicillin-susceptible S. aureus strains, as well as eight foodborne pathogens. Additionally, the conjugates showed no cytotoxic activity towards human Chang liver and mouse macrophage RAW264.7 cells.

Metabolite profiling driven analysis of Salsola species and their anti-acetylcholinesterase potential

Over 100 species of the genus Salsola are distributed in dry, arid parts of Asia, Europe and Africa, of which many species are recognised as antifungal, anticancer, antihypertensive and anthelmintic agents. Egyptian Salsola received scant characterisation of either its phytochemical composition or its biological effects. In this study, the metabolite profiles of two Salsola species viz. S. vermiculata and S. tetrandra were characterised in the aerial portions and root via ultra-performance liquid chromatography high-resolution qTOF-MS and NMR. Identified metabolites belonged to various classes including hydroxycinnamic acid conjugates, flavonoids, oxygenated fatty acids and alkaloids. Principal component analysis of derived biochemical profiles was also used for species and/or organs classification. Roots were enriched in hydroxycinnamic acid conjugates, whereas flavonoids were more abundant in aerial parts with kaempferol derivatives as major flavonoids in S. tetrandra versus quercetin in S. vermiculata. The root of S. vermiculata exhibited strong anti-acetylcholinesterase activity relative to eserine standard.

Effects of Latitude and Weather Conditions on Phenolic Compounds in Currant (Ribes spp.) Cultivars

Effects of growth latitude and weather conditions on phenolic compounds of currants (Ribes spp.) were investigated. The berries of red currant cultivar 'Red Dutch', white currant 'White Dutch', and green currant 'Vertti' were collected in seven consecutive years from two growth sites (south and north) with a latitudinal distance of 690 km. The contents of hydroxycinnamic acid conjugates and flavonol glycosides in 'Vertti' were higher than those in 'White Dutch' by 8 and 5 times, respectively, and by 50 and 3 times than those in 'Red Dutch', respectively. The total content of phenolic compounds was 10-19% higher in the north than in the south (p < 0.05). In 'Red Dutch', anthocyanins were 12% richer in berries from the north compared with those from the south (p < 0.05). The total content of hydroxycinnamic acid conjugates in 'Vertti' and 'White Dutch' from the north was 30% higher than those from the south (p < 0.05). High radiation and temperature were associated with low contents of the major phenolic compounds in all the cultivars studied. High humidity correlated with low levels of hydroxycinnamic acid conjugates in green and white currants.

Diversity of (dihydro) hydroxycinnamic acid conjugates in Colombian potato tubers

In potato tuber, caffeic acid (the predominant hydroxycinnamic acid (HCA)), its conjugates (HCAcs; i.e. chlorogenic acid (ChA), crypto-ChA, and neo-ChA), and anthocyanin-linked HCAs have been extensively described in the literature. In contrast, only little information is available on the occurrence of other HCAcs and didydrohydroxycinnamic acid conjugates (DHCAcs). Fifteen Colombian potato cultivars were screened for these less commonly described conjugates by reversed-phase ultrahigh performance liquid chromatography coupled to a diode array detector and a heated electrospray ionisation mass spectrometer. A total of 62 HCAs/HCAcs/DHCAcs were found in extracts from peel and flesh. Among them, only twelve compounds were common to all cultivars in both peel and flesh. The less commonly described compounds accounted for 7.1–20.1% w/w of the total amount of HCAs/HCAcs/DHCAcs in whole tubers, highlighting their contribution to the total phenolic profile of potato tubers. Among all cultivars, the abundance (mg/100g DW whole tuber) of neo-ChA (0.8–7.4) ranged in similar quantities as the less commonly reported feruloyl octopamine (1.2–5.2), 5-O-feruloyl quinic acid (0.1–7.5), cis-ChA (1.1–2.2), caffeoyl putrescine (0.6–2.5), sinapoyl hexose (0.1–1.8), N1,N14-bis-(dihydrocaffeoyl) spermine (0.2–1.7), N1,N10-bis-(dihydrocaffeoyl) spermidine (1.1–2.6), and N1,N5,N14-tris-(dihydrocaffeoyl) spermine (trace – 11.1).

Production of hydroxycinnamoyl-shikimates and chlorogenic acid in Escherichia coli: production of hydroxycinnamic acid conjugates

BackgroundHydroxycinnamates (HCs) are mainly produced in plants. Caffeic acid (CA), p-coumaric acid (PA), ferulic acid (FA) and sinapic acid (SA) are members of the HC family. The consumption of HC by human might prevent cardiovascular disease and some types of cancer. The solubility of HCs is increased through thioester conjugation to various compounds such as quinic acid, shikimic acid, malic acid, anthranilic acid, and glycerol. Although hydroxycinnamate conjugates can be obtained from diverse plant sources such as coffee, tomato, potato, apple, and sweet potato, some parts of the world have limited availability to these compounds. Thus, there is growing interest in producing HC conjugates as nutraceutical supplements.ResultsHydroxycinnamoyl transferases (HCTs) including hydroxycinnamate-CoA shikimate transferase (HST) and hydroxycinnamate-CoA quinate transferase (HQT) were co-expressed with 4-coumarateCoA:ligase (4CL) in Escherichia coli cultured in media supplemented with HCs. Two hydroxycinnamoyl conjugates, p-coumaroyl shikimates and chlorogenic acid, were thereby synthesized. Total 29.1 mg/L of four different p-coumaroyl shikimates (3-p-coumaroyl shikimate, 4-p-coumaroyl shikimate, 3,4-di-p-coumaroyl shikimate, 3,5-di-p-coumaroyl shikimate, and 4,5-di-p-coumaroyl shikimate) was obtained and 16 mg/L of chlorogenic acid was synthesized in the wild type E. coli strain. To increase the concentration of endogenous acceptor substrates such as shikimate and quinate, the shikimate pathway in E. coli was engineered. A E. coli aroL and aroK gene were mutated and the resulting mutants were used for the production of p-coumaroyl shikimate. An E. coli aroD mutant was used for the production of chlorogenic acid. We also optimized the vector and cell concentration optimization.ConclusionsTo produce p-coumaroyl-shikimates and chlorogenic acid in E. coli, several E. coli mutants (an aroD mutant for chlorogenic acid production; an aroL, aroK, and aroKL mutant for p-coumaroyl-shikimates production) were made and each mutant was tested using an optimized construct. Using this strategy, we produced 235 mg/L of p-coumaroyl-shikimates and 450 mg/L of chlorogenic acid.

Compositional Differences of Phenolic Compounds between Black Currant (Ribes nigrum L.) Cultivars and Their Response to Latitude and Weather Conditions

Phenolic compounds in black currants of three Finnish cultivars and their response to growth latitude and weather conditions were analyzed over a six-year period. 'Melalahti' had lower contents of total phenolic compounds (31.4% and 29.2% lower than 'Mortti' and 'Ola', respectively), total anthocyanins (32.6% and 30.5%), and total hydroxycinnamic acid derivatives (23.1% and 23.8%) (p < 0.05) and was less affected by growth latitude and weather conditions than 'Mortti' and 'Ola'. However, all the cultivars grown at higher latitude (66°34' N) had lower contents of total flavonols, total anthocyanins, and total phenolic compounds than those grown at lower latitude (60°23' N) (p < 0.05). The content of total hydroxycinnamic acid conjugates did not vary in 'Melalahti' (p > 0.05) but increased as the latitude increased in 'Mortti' and 'Ola' (p < 0.05). Temperature and radiation were the major weather variables influencing the composition of phenolic compounds. Delphinidin-3-O-glucoside, delphinidin-3-O-rutinoside, and myricetin-3-O-glucoside content showed positive correlations with temperature and radiation in all three cultivars. The study gives important guidelines for the selection of raw materials and growth sites as well as for the berry cultivation for commercial exploitation of black currant berries.

Isolation, identification and quantitation of hydroxycinnamic acid conjugates, potential platform chemicals, in the leaves and stems of Miscanthus × giganteus using LC–ESI-MS n

Miscanthus × giganteus is a source of platform chemicals and bioethanol through fermentation. Cinnamates in leaves and stems were analysed by LC–ESI-MS n . Free phenols were extracted and separated chromatographically. More than 20 hydroxycinnamates were identified by UV and LC–ESI-MS n . Comparative LC–MS studies on the leaf extract showed isomers of O-caffeoylquinic acid (3-CQA, 4-CQA and 5-CQA), O-feruloylquinic acid (3-FQA, 4-FQA and 5-FQA) and para-coumaroylquinic acid (3- pCoQA and 5- pCoQA). Excepting 3- pCoQA, all were also detected in stem. 5-CQA dominated in leaf; a mandelonitrile–caffeoylquinic acid dominated in stem. Three minor leaf components were distinguished by fragmentation patterns in a targetted MS 2 experiment as dicaffeoylquinic acid isomers. Others ( M r 516) were tentatively identified as hexosylcaffeoyl-quinates. Three positional isomers of O-caffeoylshikimic acid were minor components. p-Hydroxybenzaldehyde was also a major component in stem. This is the first report of the hydroxycinnamic acid profile of leaves and stems of M. × giganteus.

Two New Antioxidant Malonated Caffeoylquinic Acid Isomers in Fruits of Wild Eggplant Relatives

Fruits of the cultivated eggplant species Solanum melongena and its wild relative Solanum incanum have a high content of hydroxycinnamic acid conjugates, which are implicated in the human health benefits of various fruits and vegetables. Monocaffeoylquinic acid esters, in particular 5-O-(E)-caffeoylquinic acid, are usually predominant in solanaceous fruits and tubers. Two closely related caffeoylquinic acid derivatives with longer C(18) HPLC retention times than those of monocaffeoylquinic acids are minor constituents in cultivated eggplant fruit. In a prior study, the two compounds were tentatively identified as 3-O-acetyl- and 4-O-acetyl-5-O-(E)-caffeoylquinic acids and composed ≤2% of the total hydroxycinnamic acid conjugates in fruit of most S. melongena accessions. It was recently found that the pair of these caffeoylquinic acid derivatives can compose 15-25% of the total hydroxycinnamic acid conjugates in fruits of S. incanum and wild S. melongena. This facilitated C(18) HPLC isolation and structural elucidation using (1)H and (13)C NMR techniques and HR-ToF-MS. The isomeric compounds were identified as 3-O-malonyl-5-O-(E)-caffeoylquinic acid (isomer 1) and 4-O-(E)-caffeoyl-5-O-malonylquinic acid (isomer 2). Both exhibited free radical scavenging activity, albeit about 4-fold lower than that of the flavonol quercetin dihydrate. By contrast, the iron chelation activities of isomers 1 and 2, respectively, were about 3- and 6-fold greater than that of quercetin dihydrate. Reports of malonylhydroxycinnamoylquinic acids are rare, and only a few of these compounds have been structurally elucidated using both NMR and MS techniques. To the authors' knowledge, these two malonylcaffeoylquinic acid isomers have not previously been reported.

Interaction of hydroxycinnamic acids and their conjugates with organic anion transporters and ATP‐binding cassette transporters

Hydroxycinnamic acids are abundant antioxidants in our diet. In humans, hydroxycinnamic acids are metabolized to form sulfates and glucuronides, with the majority recovered in urine. We assessed the potential roles of organic anion transporters (OATs) and ATP-binding cassette (ABC) transporters in the renal uptake and efflux of hydroxycinnamic acid conjugates. Uptake studies using OAT1 (SLC22A6)-, OAT2 (SLC22A7)-, and OAT3 (SLC22A8)-expressing 293H embryonic kidney cells showed that OAT1 and OAT3, but not OAT2, accepted hydroxycinnamic acid conjugates as substrates. OAT1 and OAT3 mediated the basolateral uptake of hydroxycinnamic acid sulfates and glucuronide conjugates, respectively. Hydroxycinnamic acid sulfates are substrates of OAT4 and were capable of trans-stimulating 5-carboxyfluorescein uptake mediated by OAT4. On the other hand, hydroxycinnamic acid conjugates are not substrates for the ABC transporters, multidrug resistance protein 2 (MRP2/ABCC2) or breast cancer resistance protein (BCRP/ABCG2), demonstrated by the inability to alter ATPase activity. Cis-inhibition studies with OATs and MRPs revealed that hydroxycinnamic acid conjugates have limited impact on the transport of model substrates significantly at physiological concentrations. Concerted action of OAT1, OAT3, and OAT4 is involved in the elimination of hydroxycinnamic acid conjugates into urine, whereas MRP2 and breast cancer resistance protein are not involved in the disposition of these conjugates.

Identification and quantification of (dihydro) hydroxycinnamic acids and their conjugates in potato by UHPLC–DAD–ESI-MSn

Hydroxycinnamic acid conjugates (HCAcs) and dihydrohydroxycinamic acid conjugates (DHCAcs) were identified and quantified in potato tuber extracts by UHPLC–DAD–ESI-MSn. The HCAcs and DHCAcs identification took place by screening for product ions and neutral losses in combination with UV spectra. Thirty-nine HCAcs/DHCAcs were detected, including 17 previously reported in potato. HCAs were found unconjugated, linked to hydroxyl-containing compounds including hexose, quinic acid and malic acid, to amino-containing compounds, such as putrescine and octopamine, and to unknown compounds. DHCAs were present linked to spermine, spermidine and to still unidentified compounds. Chlorogenic acid was the most abundant compound (25.43±0.49mg/gDW) followed by cryptochlorogenic acid (7.31±0.38mg/gDW), a non-hydrolyzable sinapic acid conjugate (2.80±0.06mg/gDW) and neochlorogenic acid (2.41±0.10mg/gDW), in total accounting for 83% (w/w) of the total concentration of HCAs/DHCAs-containing compounds. Quantifications of HCAs released after alkaline hydrolysis matched well with the quantification of the unhydrolyzed molecules. The UHPLC–DAD–ESI-MSn method showed a larger diversity of HCAcs and DHCAcs in potato than described before.

New 5-O-Caffeoylquinic Acid Derivatives in Fruit of the Wild Eggplant Relative Solanum viarum

Fruit of the cultivated eggplant species Solanum melongena, Solanum aethiopicum, and Solanum macrocarpon, and wild relatives including Solanum anguivi and Solanum incanum, have a high content of hydroxycinnamic acid conjugates with potential human health benefits. Typically, caffeoylquinic acid esters predominate, and in particular 5-O-(E)-caffeoylquinic acid. By contrast, fruit from accession PI 319855 in the USDA eggplant core collection, unambiguously identified as Solanum viarum by morphological characters, were found to include several major, closely related hydroxycinnamic acid conjugates with much longer C18-HPLC retention times than those of 5-O-(E)-caffeoylquinic acid and other monocaffeoylquinic acid isomers. Four of these compounds were isolated from methanolic extracts of lyophilized fruit tissues by C18-HPLC, and structurally elucidated using (1)H and (13)C NMR techniques and HR-TOF-MS. Isomeric compounds 1 and 2 are composed of 5-O-(E)-caffeoylquinic acid with a malonyl group on the 3- or 4-hydroxyl of quinic acid, respectively, plus a 6-O-sinapoylglucose group 1-O-β-D linked with the 4-hydroxyl on the phenyl ring of the caffeoyl moiety (1β,4β-dihydroxy-3β-carboxyacetoxy- and 1β,3β-dihydroxy-4β-carboxyacetoxy-5α-[[3-[4-[1β-(6-O-(E)-sinapoyl-β-D-glucopyranosyl)oxy]-3-hydroxyphenyl]-(E)-1-oxo-2-propenyl]oxy]cyclohexanecarboxylic acid). Compound 3 has the same structure as 1 and 2 without malonation of quinic acid (1β,3β,4β-trihydroxy-5α-[[3-[4-[1β-(6-O-(E)-sinapoyl-β-d-glucopyranosyl)oxy]-3-hydroxyphenyl]-(E)-1-oxo-2-propenyl]oxy]cyclohexanecarboxylic acid). Compound 4 differs from 3 by methylation of the carboxyl group on quinic acid (methyl 1β,3β,4β-trihydroxy-5α-[[3-[4-[1β-(6-O-(E)-sinapoyl-β-D-glucopyranosyl)oxy]-3-hydroxyphenyl]-(E)-1-oxo-2-propenyl]oxy]cyclohexanecarboxylate). Some features of these four new compounds, such as malonation and the specific linkages between caffeoyl, glucosyl, and sinapoyl moieties, are common in acylated and glycosylated phenylpropanoids, but have not previously been reported in complex derivatives of 5-O-(E)-caffeoylquinic acid.