Dicaffeoylquinic Acid Isomers Research Articles

UHPLC-ESI-QqTOF-MS/MS characterization of minor chlorogenic acids in roasted Coffea arabica from different geographical origin.

Chlorogenic acids are relevant coffee quality markers, taste, and aroma precursors as well as important bioactive compounds. A number of mono-acyl, di-acyl, and tri-acyl quinic acid isomers were found in green coffee beans, being mono-caffeoyl, mono-feruloyl, mono-p-coumaroyl, and di-caffeoylquinic acid isomers considered as quantitatively major compounds. Roasting process increases the chemical complexity of coffee by inducing the formation of a number of lactones (quinides), shikimates, and other chlorogenic acids derivatives. So far, little attention has been paid in characterizing minor chlorogenic acids and derivatives in roasted Coffea arabica, also known as Arabica. In the present work, roasted C. arabica samples from different geographical origins (Brazil, Colombia, Costa Rica, Ethiopia, Guatemala, and India) were characterized by UHPLC-ESI-QqTOF-MS/MS. Several minor chlorogenic acid isomers were identified. In particular, HR-MS/MS provided putative identification of four dimethoxycinnamoyl-quinic acid derivatives, such as 4-dimethoxycinnamoylquinic acid, 4-dimethoxycinnamoyl-3-caffeoylquinic acid, 3-dimethoxycinnamoyl-4-feruloylquinic acid, 4-dimethoxycinnamoyl-5-feruloylquinic acid, and two caffeoyl, feruloyl quinic acid derivatives (3-caffeoyl-4-feruloylquinic acid and 3-feruloyl-4-caffeoylquinic acid). To our knowledge, these compounds were found in roasted Arabica coffee for the first time, and their presence is independent on the different geographical origins examined.

Mechanism underlying inhibitory effect of six dicaffeoylquinic acid isomers on melanogenesis and the computational molecular modeling studies

Dicaffeoylquinic acid (DCQA), which contain 2 caffeic acids and a quinic acid, is 6 isomeric compounds (1,3-, 1,4-, 1,5-, 3,4-, 3,5-, and 4,5-DCQA). In this study, the mechanism underlying the inhibitory effect of DCQA isomers on melanogenesis in B16F1 murine melanoma cells stimulated by melanocyte stimulating hormone (α-MSH) was evaluated. DCQA isomers showed inhibitory effects on melanogenesis in α-MSH-stimulated B16F1 cells. Furthermore, the anti-melanogenesis activities of 1,5-DCQA and 4,5-DCQA were 61% and 84%, respectively, which were greater than that of arbutin (35%). For cell-free tyrosinase, 3,4-DCQA and 4,5-DCQA indicated high inhibitory effects, similar to the activity to arbutin (35%) at 25 μM. DCQA isomers inhibited the melanogenic enzymes including tyrosinase and dopachrome tautomerase (DCT) on α-MSH-stimulated B16F1 cells. Interestingly, 4,5-DCQA, the most potent inhibitor of melanogenesis among the six DCQA isomers, significantly downregulated the expression of microphthalmia-associated transcription factor (MITF), tyrosinase-related protein 1 (TRP1) containing tyrosinase, and DCT. In particular, the inhibitory mechanism of 4,5-DCQA on MITF expression was elucidated, revealing that 4,5-DCQA inhibits the phosphorylation of cAMP response element-binding protein (CREB) by attenuating cAMP generation during melanogenesis. A molecular docking study was conducted to elucidate the inhibitory mechanism of 4,5-DCQA on cAMP production. DCQA isomers dock to the residues of adenylyl cyclase with a distance of <3 Å, except for 1,3-DCQA. Especially, 4,5-DCQA showed Full Fitness of −1304.68 kcal/mol and △G of −8.33 kcal/mol, as well as H-bonding with adenylyl cyclase at ILE953 and LYS930 residues. In conclusion, DCQA isomers have different effects on melanogenesis depending on their structure. Especially, 4,5-DCQA has depigmentation activity through the inhibitory effect on cellular tyrosinase directly and binding effect on adenylyl cyclase, resulting in the downregulation of MITF protein, thereby reducing the expression of melanogenic enzymes.

Chemical profiling of infusions and decoctions of Helichrysum italicum subsp. picardii by UHPLC-PDA-MS and in vitro biological activities comparatively with green tea (Camellia sinensis) and rooibos tisane (Aspalathus linearis)

Several medicinal plants are currently used by the food industry as functional additives, for example botanical extracts in herbal drinks. Moreover, the scientific community has recently begun focusing on halophytes as sources of functional beverages. Helichrysum italicum subsp. picardii (everlasting) is an aromatic halophyte common in southern Europe frequently used as spice and in traditional medicine. In this context, this work explored for the first time H. italicum subsp. picardii as a potential source of innovative herbal beverages with potential health promoting properties. For that purpose, infusions and decoctions were prepared from roots, vegetative aerial-organs (stems and leaves) and flowers and evaluated for in vitro antioxidant and anti-diabetic activities. Samples were also assessed for toxicity in different mammalian cell lines and chemically characterized by spectrophotometric methods and ultra-high performance liquid chromatography–photodiode array–mass-spectrometry (UHPLC-PDA-MS). Results were expressed relating to ‘a cup-of-tea’ and compared with those obtained with green tea (Camellia sinensis) and rooibos tisane (Aspalathus linearis). Tisanes from the everlasting’s above-ground organs, particularly flowers, have high polyphenolic content and several phenolics were identified; the main compounds were chlorogenic and quinic acids, dicaffeoylquinic-acid isomers and gnaphaliin-A. The antioxidant activity of beverages from the everlasting’s above-ground organs matched or surpassed that of green tea and rooibos. Its anti-diabetic activity was moderate and toxicity low. Overall, our results suggest that the everlasting is a potential source of innovative and functional herbal beverages.

Profiling and elucidation of the phenolic compounds in the aerial parts of Gynura bicolor and G. divaricata collected from different Chinese origins.

Gynura bicolor and G. divaricata are not only known to be nutritive as cultured vegetables, but also beneficial as folk medicines in East Asia. As demonstrated by the current phytochemical knowledge, the genus Gynura is a promising source of phenolics with multiple medicinal activities. To expand this phytochemical knowledge, the phenolic secondary metabolites of G. bicolor and G. divaricata were studied. From the aerial parts of these two species, collected in five different Chinese locations, two fractions of phenolic compounds with different polarity were obtained by extraction and chromatographic separation. Using UPLC/MS/MS analysis, a total of 53 phenolics were either identified by comparison with respective reference compounds or tentatively characterized by their chromatographic behavior, UV-absorption patterns, and MS fragmentations. Some naturally existing positional isomers of O-caffeoylquinic acid, O-p-coumaroylquinic acid, O-feruloylquinic acid, and dicaffeoylquinic acid as well as their methyl esters were qualitatively characterized by their specific fragmentation patterns in targeted MS/MS. In addition, the aerial parts of the two Gynura species contained kaempferol, quercetin oligoglycosides, and a variety of derivatives of benzoic acid, hydroxycinnamic acid, and caffeic acid. Furthermore, the distribution of phenolic compounds in the two species from different Chinese origins was discussed. Finally, an investigation of the total phenolic content and in vitro antioxidant activity of the various phenolic fractions was completed, to evaluate the potential of the extracts of these species for medicinal development. The free-radical-scavenging activities of the extracts derived from plants originating from Nanjing were proven to be higher than those of the other extracts, which correlated well with their total phenolic content.

Metabolic profiling of Goji berry extracts for discrimination of geographical origin by non-targeted liquid chromatography coupled to quadrupole time-of-flight mass spectrometry

The fruit of Lycium barbarum (Solanaceae), known as Goji berry, or wolfberry, has long been used in traditional Chinese medicine, and is increasingly becoming popular in Western diets due to its potential health benefits.The majority of commercially produced Goji berries come from certain regions in Asia. In this study we explored the discrimination of phytochemical content between four different geographic origins of Goji berries by applying non-targeted liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (LC–qTOF–MS) metabolite profiling. Principal component analysis was able to clearly distinguish the berries by the geographic origin when applied to the non-targeted profiling data of Mongolian, Chinese and two Tibetan origin Goji berry extracts. Furthermore, partial least squares discriminant analysis (PLS-DA) provided indicative markers of discrimination between the different origins, and quality threshold cluster analysis classified the most discriminative compounds according to their occurrence between the different origins. The largest cluster included the most discriminative metabolites in the Mongolian variety, which was also seen as the most distant group in the PCA analysis as compared to the other countries of origin.Mongolian Goji berries were mainly characterized by significantly higher levels of several flavonol glycosides, such as quercetin and kaempferol glycosides; isomers of dicaffeoylquinic acid and phenolic acids such as coumaric acid. In addition to the various phytochemical metabolites identified, a pesticide compound was found especially in the extracts of Goji berries from China.The present non-targeted metabolite profiling proved to be a useful approach of the Foodomics field for assessment of geographical origin of berries.

Identification of phenolic constituents in Cichorium endivia var. crispum and var. latifolium salads by high-performance liquid chromatography with diode array detection and electrospray ioniziation tandem mass spectrometry.

Chicory is a widely consumed vegetable and a source of phenolic compounds. Phenolic acid and flavonoid derivatives were identified in Cichorium endivia var. crispum and var. latifolium and fully characterized using complementary information from two different high-performance liquid chromatography detectors, diode array and mass spectrometer, in positive and negative modes. We describe about 40 phenolic compounds, some of which have never previously been reported in these plants, such as hydroxycinnamic acid derivatives (i.e., different mono- and dicaffeoylquinic acid isomers) and mono- and diglycosides of quercetin, kaempferol, and myricetin (differing also by the glycosylation site). These data provide a contribution to a more exhaustive identification of phenolic compounds in C. endivia vegetables.

HPLC–MSn Analysis of Organic Acids and Glycosides in Qi-gui-yin Granules

In this study, a systematic method was established for the global quality control of Qi-gui-yin granules, a five-herb Traditional Chinese Patent Medicine for the treatment of multiple drug-resistant Pseudomonas aeruginosa infections. Identification of organic acids and glycosides was conducted in this paper, and a fast and sensitive method based on high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry was established for rapid separation and sensitive identification. Samples were separated on a Agilent SB C18 column (150 × 4.6 mm, 5 μm) by gradient elution using acetonitrile (A) and water–formic acid (B; 0.03 %, v/v) as mobile phase at a flow rate of 1.0 ml/min. Based on the mass spectra and retention time, 12 organic acids, 12 glycosides, and the other 7 compounds were identified or tentatively characterized. In this paper, five isomers of chlorogenic acid (caffeoylquinic acid) and four isomers of dicaffeoylquinic acid were reported; the fragment ions in mass spectrum of two isomers of chlorogenic acid were different from reported CQA, so we presume that they are new isomers of chlorogenic acid. Furthermore, it was found that the characteristic fragmentation reaction of glycosides was through the homolytic cleavage of the O-glycosidic bond to produce radical aglycone ion, and different glycoside compounds were suitable for different ionization conditions. Their fragmentation pathway was summarized, and the fragmentation pathway of all kinds of compounds was summarized to enrich the data. These characteristics can be used for structure elucidation of similar compounds.

Antioxidant and DNA-Protective Activities of Chlorogenic Acid Isomers

Chlorogenic acid is a well-known antioxidant and has more isomers according to the difference in binding location and number of caffeic on quinic acid. In this study, we investigated and compared the profiles of antioxidant and DNA-protective activities of chlorogenic acid isomers including three caffeoylquinic acid isomers (3-O-caffeoylquinic acid, 3-CQA; 4-O-caffeoylquinic acid, 4-CQA; and 5-O- caffeoylquinic acid, 5-CQA) and three dicaffeoylquinic acid isomers (3,5-dicaffeoyl-quinic acid, ICAA; 3,4-dicaffeoylquinic acid, ICAB; and 4,5-dicaffeoyl-quinic acid, ICAC). The results showed that each of chlorogenic acid isomers studied exhibited antioxidant activities and DNA damage protective effects to various extents. On the whole, dicaffeoylquinic acids possessed better antioxidant activities, mostly because they have more hydroxyl groups than caffeoylquinic acids. Three caffeoylquinic acid isomers showed quite similar antioxidant activities, indicating that the position of esterification on the quinic moiety of caffeoylquinic acid had no effect on its antioxidant activities. Quite the contrary, a difference among dicaffeoylquinic acid isomers was observed, namely, ICAA and ICAB exhibited the same antioxidant activities, whereas ICAC had higher antioxidant activities than ICAA and ICAB in some assays, which implied that their antioxidant activities were probably influenced by the position of esterification on the quinic moiety. We speculated that this difference might be due to the fact that there may exist a steric hindrance effect in the ICAC. However, this assumption needs to be further confirmed.

Antioxidant activity of phenolic compounds identified in sunflower seeds

The antioxidant activity and phenolic compound profiles of six fractions (I–VI) obtained from sunflower seed extract were studied. HPLC–MS(ESI) analysis was applied for quantitative and qualitative determination of phenolic compounds of the fractions. The antioxidant activity of the fractions was studied in terms of their ability to scavenge DPPH· and ABTS·+ and to reduce Fe3+/ferricyanide complex to the ferrous form and was expressed as EC50, TEAC and reducing power values, respectively. The results of all antioxidant activity tests showed good correlations among each other and with the phenolic contents for the individual fractions. The fractions IV–VI were characterized by high antioxidant activity. 5-O-Caffeoylquinic acid was a predominant compound of fractions IV and V, while dicaffeoylquinic acid isomers and caffeoyl-dimethoxycinnamoylquinic acid isomers accounted for 76.6 % of phenolic compounds of fraction VI. Ferulic acid, p-coumaroylquinic acid isomers, ferulic acid dehydrotrimer isomers and some quercetin derivatives were also identified. The highest content of those compounds was noted in fraction III.

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.

Simultaneous determination of phenolic acids and flavonoids in Lycium barbarum Linnaeus by HPLC–DAD–ESI-MS

A high-performance liquid chromatography–diode array detection–mass spectrometry method with electrospray ionization mode (HPLC–DAD–ESI-MS) was developed for simultaneous determination of phenolic acids and flavonoids in fruits of Lycium barbarum Linnaeus, a widely used traditional Chinese herb possessing vital biological activity. Both phenolic acids and flavonoids were extracted with 50% ethanol and purified using a polymeric solid phase extraction cartridge followed by HPLC–DAD–ESI-MS analysis. By employing a Vydac C18 column, a total of 52 phenolic acids and flavonoids were separated within 70 min using a gradient mobile phase of 0.5% (v/v) formic acid in water and acetonitrile–water (94:6, v/v) with flow rate at 1 mL/min, column temperature at 30 °C and detection wavelength at 280 nm. Of 52 compounds, 15 phenolic acids and flavonoids were positively identified based on both absorption and mass spectra, with the remaining 37 tentatively identified by comparison of absorption spectra with reported values in the literature. Internal standards 3-hydroxybenzoic acid and hesperidin were used for quantitation of phenolic acids and flavonoids, respectively. Among the 15 positively identified compounds, quercetin-rhamno-di-hexoside was present in largest mass fraction (438.6 μg/g), followed by quercetin-3-O-rutinoside (281.3 μg/g), dicaffeoylquinic acid isomers (250.1 μg/g), chlorogenic acid (237.0 μg/g), quercetin-di-(rhamnohexoside) (117.5 μg/g), quercetin-di-(rhamno)-hexoside (116.8 μg/g), kaempferol-3-O-rutinoside (97.7 μg/g), isorhamnetin-3-O-rutinoside (72.1 μg/g), p-coumaric acid (64.0 μg/g), caffeic acid (23.7 μg/g) and vanillic acid (22.8 μg/g).

Effects of Different Cooking Methods on Antioxidant Profile, Antioxidant Capacity, and Physical Characteristics of Artichoke

In this study, the effects of three common cooking practices (i.e., boiling, steaming, and frying) on the artichoke phenolic compounds pattern were evaluated by LC-MS/MS analysis. The variation of carotenoids, antioxidant capacity, and artichoke physical properties after cooking was also investigated. The major phenolic compounds present in the raw sample were 5- O-caffeoylquinic and 1,5-di- O-caffeoylquinic acids; after cooking treatments, an increase of the overall caffeoylquinic acids concentration due to the formation of different dicaffeoylquinic acid isomers was observed. Steamed and fried samples showed similar patterns of dicaffeoylquinic concentrations, which were higher with respect to the boiled samples. On the other hand, all cooking practices, particularly frying, decreased flavonoid concentration. The antioxidant capacity of cooked artichokes, measured by three different assays, enormously increased after cooking, particularly after steaming (up to 15-fold) and boiling (up to 8-fold). The observed cooking effect on the artichoke antioxidant profile is probably due to matrix softening and increased extractability of compounds, but the increase of antioxidant capacity is much higher than the increase of antioxidant concentration. These results suggest that some common cooking treatments can be used to enhance the nutritional value of vegetables, increasing bioaccessibility of health-promoting constituents.

Stress-Induced Biosynthesis of Dicaffeoylquinic Acids in Globe Artichoke

Leaf extracts from globe artichoke ( Cynara cardunculus L. var. scolymus) have been widely used in medicine as hepatoprotectant and choleretic agents. Globe artichoke leaves represent a natural source of phenolic acids with dicaffeoylquinic acids, such as cynarin (1,3-dicaffeoylquinic acid), along with its biosynthetic precursor chlorogenic acid (5-caffeoylquinic acid) as the most abundant molecules. This paper reports the development of an experimental system to induce caffeoylquinic acids. This system may serve to study the regulation of the biosynthesis of (poly)phenolic compounds in globe artichoke and the genetic basis of this metabolic regulation. By means of HPLC-PDA and accurate mass LC-QTOF MS and MS/MS analyses, the major phenolic compounds in globe artichoke leaves were identified: four isomers of dicaffeoylquinic acid, three isomers of caffeoylquinic acid, and the flavone luteolin 7-glucoside. Next, plant material was identified in which the concentration of phenolic compounds was comparable in the absence of particular treatments, with the aim to use this material to test the effect of stress application on the regulation of biosynthesis of caffeoylquinic acids. Using this material, the effect of UV-C, methyl jasmonate, and salicylic acid treatments on (poly)phenolic compounds was tested in different globe artichoke genotypes. UV-C exposure consistently increased the levels of dicaffeoylquinic acids in all genotypes, whereas the effect on compounds from the same biosynthetic pathway, for example, chlorogenic acid and luteolin-7-glucoside, was much less pronounced and was not statistically significant. No effect of methyl jasmonate or salicylic acid was found. Time-response experiments indicated that the level of dicaffeoylquinic acids reached a maximum at 24 h after UV radiation. On the basis of these results a role of dicaffeoylquinic acids in UV protection in globe artichoke is hypothesized.

Phenolic composition and antioxidant capacity of different heat‐processed forms of sweetpotato cv. ‘Beauregard’

SummarySweetpotato [Ipomoea batatas (L.) Lam.] cv. ‘Beauregard’ roots were cooked using three different heat‐processing techniques (baked in a conventional oven, baked in a microwave oven, and boiled). Total phenolic content, individual phenolic acids, and antioxidant capacity were determined using Folin‐Denis assay, HPLC (high‐performance liquid chromatography), and DPPH (1,1‐diphenyl‐2‐picrylhydazyl) assay, respectively. The skin tissue (raw or processed) contained the highest concentration of total phenolics. All heat‐processing methods resulted in a significant loss in total phenolic content and antioxidant capacity of the skin tissue. However, compared with the other processing methods, conventional oven baking resulted in greater losses in antioxidant capacity of skin tissue. Total phenolic content ranged from a low of 1.58 mg chlorogenic acid equivalent g−1 dry tissue weight in boiled pith tissue to a high of 17.7 mg chlorogenic acid equivalent g−1 dry tissue weight in raw skin tissue. The antioxidant capacity was highest in raw skin tissue (22.9 mg Trolox equivalent g−1 dry tissue weight). Chlorogenic acid was the principal phenolic acid found in all sweetpotato tissues. Caffeic acid and three isomers of dicaffeoylquinic acid (diCQA) were also identified and quantified.

Contents of Caffeoylquinic Acid Compounds in the Storage Roots of Sixteen Sweetpotato Genotypes and Their Potential Biological Activity

Caffeoylquinic acid compounds are widespread in plants. They protect plants against predation and infection and may have several beneficial functions in the human diet. The contents of chlorogenic acid and the 3,4-, 3,5-, and 4,5- isomers of dicaffeoylquinic acid (DCQA) in the storage root tissues of 16 sweetpotato [Ipomoea batatas (L.) Lam.] genotypes were determined. Averaged over genotypes, the contents of the four compounds were highest in the cortex, intermediate in the stele, and lowest in the periderm. Among the genotypes, chlorogenic acid contents ranged from 16 to 212 μg·g−1 in periderm, from 826 to 7274 μg·g−1 in cortex, and from 171 to 4326 μg·g−1 in stele. The 3,5-DCQA isomer comprised over 80% of total DCQA. In most genotypes, 3,5-DCQA and chlorogenic acid contents were similar in cortex and stele tissues, but chlorogenic acid was lower than 3,5-DCQA in periderm tissue. Among the 16 genotypes, total DCQA contents ranged from 0 to 1775 μg·g−1 dry weight in periderm, from 883 to 8764 μg·g−1 in cortex, and from 187 to 4768 μg·g−1 in stele. The large differences found in a small germplasm collection suggest that selecting or breeding sweetpotato genotypes with high caffeoylquinic acid content is possible. The four caffeoylquinic acid compounds comprised over 3% of the dry weight of storage roots of the sweetpotato relative, bigroot morningglory [Ipomoea pandurata (L.) G.F.W. Meyer], indicating that it may be a good source for the compounds. The effect of DCQAs isolated from sweetpotato and I. pandurata tissue and caffeic and chlorogenic acid standards were tested in proso millet (Panicum milliaceum L.), Fusarium solani (Sacc.) Mart., and bacterial growth bioassays. Caffeic acid, chlorogenic acid, and 3,5-DCQA were most inhibitory in millet and F. solani bioassays, but 3,5-DCQA was the least inhibitory compound in bacterial growth bioassays. Their activity in the bioassays suggests that the caffeoyl quinic acid compounds contribute to the allelopathic potential and resistance to root diseases of some sweetpotato clones.

Methodology Optimization for Quantification of Total Phenolics and Individual Phenolic Acids in Sweetpotato (Ipomoea batatas L.) Roots

Phenolic acids are one of the several classes of naturally occurring antioxidant compounds found in sweetpotatoes. Simplified, robust, and rapid methodologies were optimized to quantify total and individual phenolic acids in sweetpotato roots. Total phenolic acid content was quantified spectrophotometrically using both Folin-Denis and Folin-Ciocalteu reagents. The Folin-Ciocalteu reagent gave an overestimation of total phenolic acids due to the absorbance of interfering compounds (that is, reducing sugars and ascorbic acid). Individual phenolic acids were quantified by high-performance liquid chromatography (HPLC) using the latest in column technology. Four reversed-phase C18 analytical columns with different properties (dimensions, particle size, particle shape, pore size, and carbon load) were compared. Three different mobile phases using isocratic conditions were also evaluated. A column (4.6 x 150 mm) packed with 5-microm spherical silica particles of pore size 110 A combined with 14% carbon load provided the best and fast separation of individual phenolic acids (that is, chlorogenic acid, caffeic acid, and 3 isomers of dicaffeoylquinic acid) with a total analysis time of less than 7 min. Among the 3 mobile phases tested, a mobile phase consisting of 1% (v/v) formic acid aqueous solution: acetonitrile: 2-propanol, pH 2.5 (70:22:8, v/v/v) gave adequate separation. Among the solvents tested, aqueous mixtures (80:20, solvent:water) of methanol and ethanol provided higher phenolic acid extraction efficiency than the aqueous mixture of acetone.

LC/MS characterization of phenolic constituents of mate (Ilex paraguariensis, St. Hil.) and its antioxidant activity compared to commonly consumed beverages

Mate is a tea-like beverage widely consumed in South America, prepared from the dried leaves of Ilex paraguariensis, St Hil. The total polyphenols (PP) and antioxidant activity of mate infusions and acid–methanol/acetone extracts were determined in three commercial brands, and compared to commonly consumed beverages like green and black teas, red, rose and white wines, and orange juice. Mate had a PP content comparable to tea and orange juice, and, when normalized for the PP content of beverages, mate had an antioxidant activity slightly higher than wines, orange juice and black tea, but lower than green tea. LC/MS analysis of mate extracts showed that caffeoylquinic and dicaffeoylquinic acid isomers were the major components of the phenolic fraction of mate. Mixed mono-, di- and tri-esters of quinic acid and other hydroxycinnamates were also detected. Several quercetin and kaempferol glycosides were identified. Consumption of mate infusions would significantly contribute to the overall antioxidant intake, providing high amounts of caffeoylquinic acid derivatives, with biological effects potentially beneficial for human health.

Discriminating between the Six Isomers of Dicaffeoylquinic Acid by LC-MSn

The fragmentation behavior of all six dicaffeoylquinic acids (diCQA) has been investigated using LC-MS(4). It is possible to discriminate between each of the isomers including those for which commercial standards are not available. For diCQA, the ease of removal of the caffeoyl residue during fragmentation is 1 approximately = 5 > 3 > 4. The distinctive fragmentation observed for the little-studied 1,4-dicaffeoylquinic acid involves elimination of the C1 caffeoyl residue, repeated dehydrations leading to the aromatization of the quinic acid moiety, and its decarboxylation. It is suggested that this process is initiated by the C1 carboxyl protonating the C5 hydroxyl in the inverted chair conformer, followed by its protonating the C1 caffeoyl residue in the favored chair conformation. The fragmentation of 1-caffeoylquinic acid is indistinguishable from that of the commercially available 5-caffeoylquinic acid, but these two isomers can be distinguished easily by their facile chromatographic resolution on reversed phase packings. The hierarchical key previously developed for characterizing chlorogenic acids has been extended to accommodate 1-caffeoylquinic acid and the 1-acyl dicaffeoylquinic acids.

Influence of Washing Treatment and Storage Atmosphere on Phenylalanine Ammonia-Lyase Activity and Phenolic Acid Content of Minimally Processed Carrot Sticks

The influence of washing uncut and shredded carrots (Daucus carota L. ssp. sativa var. Bangor) with chlorinated and ozonated water, respectively, as well as the storage of the produce under aerobic and anaerobic conditions, respectively, on PAL activity and synthesis of phenolic compounds have been evaluated on pilot plant scale. Inherent raw material inhomogeneity was compensated by pooling large sized samples, and frequent sampling ensured significant data. PAL activity was induced by processing and linearly increased throughout storage under aerobic conditions, whereas an anaerobic atmosphere resulted in a maximum activity peak at storage day 2-4. The accumulation of phenolic compounds showed good correlation with the kinetics of PAL activity. Although the influence of the washing treatments was weak, the use of chlorinated water for washing shredded carrots slightly delayed the onset of PAL activity. The phenolic content of the minimally processed carrots was dominated by trans and cis isomers of chlorogenic acid ( approximately 95%). Additionally, the occurrence of p-coumaroylquinic acid ( approximately 5%) and the novel finding of three dicaffeoylquinic acid isomers were reported. The synthesis of phenolic compounds was controlled, depending on storage atmosphere.

Investigation of phenolic acids in yacon (Smallanthus sonchifolius) leaves and tubers

Thin-layer chromatographic (TLC) screening of crude extracts of dried leaves and tubers of yacon (Smallanthus sonchifolius, Asteraceae) and products of acid hydrolysis of tubers on the silica gel HPTLC plates using the developing solvents ethyl acetate–formic acid–water (85:10:15, v/v/v) and n-hexane–ethyl acetate–formic acid (20:19:1, v/v/v) proved the presence of chlorogenic, caffeic and ferulic acid. These phenolic acids were isolated from the crude extract of yacon leaves by preparative TLC, and identified after elution by HPLC/MS, as well as by direct injection of the crude extract into the HPLC/MS system. Acid hydrolysis of tubers released the increased amount of phenolic acids (e.g. caffeic acid and ferulic acid), flavonoid quercetin and an unidentified flavonoid, which was detected by TLC analysis.Ferulic acid, isomers of dicaffeoylquinic acid and still an unidentified derivative of chlorogenic acid (Mr=562) as constituents of yacon leaves and ferulic acid as constituent of yacon tubers are reported here for the first time. These acids gave significant contribution to the radical scavenging activity detected directly on the TLC plate sprayed with 1,1-diphenyl-2-picrylhydrazyl (DPPH).