Chlorogenic Acid Isomers Research Articles

Transformation of chlorogenic acids during the coffee beans roasting process

Due to the recently discovered biomedical activity of chlorogen acid, the interest in its physicochemical and pharmaceutical properties has increased. The plant product most frequently mentioned as remarkably rich in this compound is coffee beans. The present paper shows that the roasting process of coffee beans not only leads to the degradation of chlorogenic acid isomers to volatile components, the fact well known from the literature, but also causes their transformation to quinic acid and its epimer and to four chlorogenic acid lactones (basic and epimeric forms of 3- and 4-O-caffeoylquinic acid lactones) and changes the ratios between the amounts of chlorogen acid isomers and dicaffeoylquinic acids isomers. It is also shown that the increase of water content above its standard level in the initial green coffee beans slows down only the changes occurring during the roasting process.

English

The present study was carried out to analyze chemical descriptors present in the raw coffee bean and to establish an association of these descriptors with the sensorial quality of the coffee beverage, based on expressions resulting from the interactions of coffee genotype, environment, and processing. The chemical descriptors caffeine, trigonelline, sucrose, and isomers of chlorogenic acid (3-CQA, 4-CQA, and 5-CQA), were analyzed through the use of high performance liquid chromatography (HPLC). Trained and qualified cuppers, certified as judges of specialty coffees, carried out the sensorial analysis using the methodology proposed by the Specialty Coffee Association of America (SCAA). Based on the cultivation environment, altitude and the genotype, it was possible to associate the chemical composition of the raw coffee bean with the coffee beverage sensorial quality. Yellow Bourbon cultivated above 1,200 m of altitude present higher contents of trigonelline and 3-CQA in the raw beans as well as high sensorial quality in the beverage. Key words: Altitude, multidimensional scaling, slope exposure, Yellow Bourbon, coffee processing.

Interactions between major chlorogenic acid isomers and chemical changes in coffee brew that affect antioxidant activities

Coffee bean source and roasting conditions significantly (p<0.05) affected the content of chlorogenic acid (CGA) isomers, several indices of browning and subsequent antioxidant values. Principal component analysis was used to interpret the correlations between physiochemical and antioxidant parameters of coffee. CGA isomer content was positively correlated (p<0.001) to capacity of coffee to reduce nitric oxide and scavenge Frémy’s salt. Indices of browning in roasted coffee were positively correlated (p<0.001) to ABTS and TEMPO radical scavenging capacity, respectively. Only the CGA content of coffee corresponded to intracellular antioxidant capacity measured in Caco-2 intestinal cells. This study concluded that the intracellular antioxidant capacity that best describes potential health benefits of coffee positively corresponds best with CGA content.

Multispectroscopic and docking studies on the binding of chlorogenic acid isomers to human serum albumin: Effects of esteryl position on affinity

Structural differences among various dietary polyphenols affect their absorption, metabolism, and bioactivities. In this work, chlorogenic acid (CA) and its two positional isomers, neochlorogenic acid (NCA) and cryptochlorogenic acid (CCA), were investigated for their binding reactions with human serum albumin (HSA) using fluorescence, ultraviolet–visible, Fourier transform infrared and circular dichroism spectroscopies, as well as molecular docking. All three isomers were bound to HSA at Sudlow’s site I and affected the protein secondary structure. CCA presented the strongest ability of hydrogen-bond formation, and both CA and NCA generated more electrostatic interactions with HSA. The albumin-binding capacity of these compounds decreased in the order CCA>NCA>CA. The compound with 4-esteryl structure showed higher binding affinity and larger conformational changes to HSA than that with 3- or 5-esteryl structures. These comparative studies on structure–affinity relationship contributed to the structural modification and design of phenolic food additives or new polyphenol-like drugs.

Analysis of a series of chlorogenic acid isomers using differential ion mobility and tandem mass spectrometry

Chlorogenic acids are among the most abundant phenolics found in the human diet. Of these, the mono-caffeoylquinic acids are the predominant phenolics found in fruits, such as apples and pears, and products derived from them. In this research, a comprehensive study of the electrospray ionization (ESI) tandem mass spectrometric (MS/MS) dissociation behavior of the three most common mono-caffeoylquinic acids, namely 5-O-caffeoylquinic acid (5-CQA), 3-O-caffeoylquinic acid (3-CQA) and 4-O-caffeoylquinic acid (4-CQA), were determined using both positive and negative ionization. All proposed structures of the observed product ions were confirmed with second-generation MS3 experiments. Similarities and differences between the dissociation pathways in the positive and negative ion modes are discussed, confirming the proposed structures and the established MS/MS fingerprints. MS/MS dissociation was primarily driven via the cleavage of the ester bond linking the quinic acid moiety to the caffeic acid moiety within tested molecules. Despite being structural isomers with the same m/z values and dissociation behaviors, the MS/MS data in the negative ion mode was able to differentiate the three isomers based on ion intensity for the major product ions, observed at m/z 191, 179 and 173. This differentiation was consistent among various MS instruments. In addition, ESI coupled with high-field asymmetric waveform ion mobility spectrometry-mass spectrometry (ESI-FAIMS-MS) was employed for the separation of these compounds for the first time. By combining MS/MS data and differential ion mobility, a method for the separation and identification of mono-caffeoylquinic in apple/pear juice samples was developed with a run time of less than 1 min. It is envisaged that this methodology could be used to identify pure juices based on their chlorogenic acid profile (i.e., metabolomics), and could also be used to detect juice-to-juice adulteration (e.g., apple juice addition to pear juice).

Phenolic Profile and Antioxidant Potential of Leaves from Selected Cotoneaster Medik. Species.

The antioxidant efficiency of 70% aqueous methanolic extracts from the leaves of twelve selected Cotoneaster Medik. species was evaluated using four complementary in vitro tests based on SET- (single electron transfer) and HAT-type (hydrogen atom transfer) mechanisms (DPPH, FRAP, O2•− and H2O2 scavenging assays). The samples exhibited the dose-dependent responses in all assays with activity parameters of EC50 = 18.5–34.5 µg/mL for DPPH; 0.9–3.8 mmol Fe2+/g for FRAP; SC50 = 27.7–74.8 µg/mL for O2•−; and SC50 = 29.0–91.3 µg/mL for H2O2. Significant linear correlations (|r| = 0.76–0.97, p < 0.01) between activity parameters and total contents of phenolics (5.2%–15.4% GAE) and proanthocyanidins (2.1%–15.0% CYE), with weak or no effects for chlorogenic acid isomers (0.69%–2.93%) and total flavonoids (0.28%–1.40%) suggested that among the listed polyphenols, proanthocyanidins are the most important determinants of the tested activity. UHPLC-PDA-ESI-QTOF-MS analyses led to detection of 34 polyphenols, of which 10 B-type procyanidins, 5 caffeoylquinic acids and 14 flavonoids were identified. After cluster analysis of the data matrix, the leaves of Cotoneaster zabelii, C. splendens, C. bullatus, C. divaricatus, C. hjelmqvistii and C. lucidus were selected as the most promising sources of natural antioxidants, exhibiting the highest phenolic levels and antioxidant capacities, and therefore the greatest potential for pharmaceutical applications.

Performance review of a fast HPLC-UV method for the quantification of chlorogenic acids in green coffee bean extracts

The aim of this study was to test the performance of a HPLC method, designated for rapid quantification of chlorogenic acids (CGA) in green coffee extract (GCE). The precision statistics associated with the method were assessed using three independent laboratories with five samples analyzed in triplicate. Seven main CGA isomers (3-CQA, 5-CQA, 4-CQA, 5-FQA, 3,4-diCQA, 3,5-diCQA and 4,5-diCQA) were quantified. The concentration of total CGA in the samples varied from 32.24% to 52.65% w/w. The repeatability and reproducibility standard deviations for the determination of individual isomers varied, respectively, from 0.01 to 0.28 and 0.05–1.59. The repeatability and reproducibility standard deviations of the calculated total CGA, corresponding to the sum of the seven main CGA isomers, varied respectively, from 0.17 to 0.58 and 0.55–2.01. The fast HPLC method evaluated in this study was considered precise and appropriate for the determination of CGA in GCE.

Capacity of chlorogenic acid isomers to modulate oxidative and inflammatory responses in Caco‐2 human enterocyte‐like cells

Chlorogenic acids (CGAs) are esters formed between caffeic and quinic acids, and represent an abundant group of plant polyphenols present in the human diet. CGAs contain different isomers, including the major ones such as 5‐caffeoylqunic acid (5‐CQA), 3‐caffeoylqunic acid, 4‐caffeoylqunic acid, 3,4‐dicaffeoylqunic acid, 3,5‐dicaffeoylquinic acid, and 4,5‐dicaffeoylqunic acid. The antioxidant and anti‐inflammatory properties of 5‐CQA have been established in both cell and animal studies. However, little is known about the ability of other major CGA isomers to modulate oxidative and inflammatory stresses. In this study, we conducted a pre‐treatment experiment in which Caco‐2 cells were exposed to individual physiological relevant concentrations of CGA isomers for 24 hours and once removed were then challenged with oxidative and inflammatory stresses. We found that the pre‐incubation of CGA isomers promoted pro‐inflammatory cytokine, interleukin 8, and activated the nuclear translocation of nuclear factor kappa B (NF‐κB) pathway. The pre‐incubation did not activate nuclear factor‐E2‐related factor 2 (Nrf2) pathway. A co‐incubation experiment was conducted in which Caco‐2 cells were firstly exposed to individual CGA isomers for 24 hours. Then, fresh CGA isomers were added before cells were challenged with oxidative and inflammatory stresses. Herein, we found that the co‐incubation treatment of CGA isomers showed anti‐inflammatory effect by attenuating the secretion of IL‐8. This was accompanied with an increase in NF‐κB signaling. We also found that CGA co‐incubation treatment significantly increased Nrf2 signaling that corresponded to increased ratio of reduced glutathione to oxidized glutathione; both indicating a mitigated oxidative stress. We proposed that CGA isomers exert anti‐inflammatory activity by activating Nrf2 signaling, even though CGA isomer activated NF‐κB pathway at the early stage of response. Our results suggest that Nrf2 is a secondary event that participates in a later negative loop of NF‐kB regulation. Cross‐talk between NF‐κB and Nrf2 seems apparent in this case.Support or Funding InformationThis work was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant.

Electrochemical Properties of Chlorogenic Acids and Determination of Their Content in Coffee Using Differential Pulse Voltammetry

The electrochemical properties of nine chlorogenic acids (CGAs) isomers: three caffeoylquinic acids, CQAs (5-CQA, 4-CQA, 3-CQA), three dicaffeoylquinic acids, diCQAs (3,4-diCQA, 3,5-diCQA, 4,5CQA) and three feruloylquinic acids, FQAs (5-FQA, 4-FQA, 3-FQA) were studied by differential pulse voltammetry (DPV) method. The study has shown that electrochemical properties of CQAs and diCQAs are strongly dependent on their chemical structure and electronic properties, particularly on presence of electron-donating –OH and –CH=CH– groups, and a strong electron-withdrawing effect of ester (–COOR) group presented in their structures. The electrochemical properties of FQAs were additionally influenced by the presence of methoxy group (–OCH3) attached on the aromatic ring. DPV measurements show that electrochemical oxidation of CQAs and diCQAs at a GCE is reversible, pH dependent, two- electron-two- proton process occured on catechol moiety in the structure of these molecules. Electrochemical oxidation of FQAs proceeded by an EC mechanism. In the first, electrochemical oxidation step, a phenoxy radical was formed by irreversible one-electron-one-proton process. In the second, chemical step, phenoxy radical undergoes hydrolysis generated a new more electroactive compound with methoxy-catechol moiety in the structure. This compound was reversible oxidised to methoxy-ortho-quionone structure by two-electron-two-proton process. The electrochemical properties of 5-CQA (main CGAs in coffee) were investigated more in detail. It was observed that anodic oxidation peak current of 5-CQA show its maximum in PBS solution of pH 7 and linear relationship within the concentration range of 5-50 mol L -1 , with LOD of 1.2·10 -6 mol L -1 . DPVs of coffee show that electrochemical properties of coffee extracts were very similar to that of investigated CGAs. Therefore, DPV was used for characterization of CGAs in coffees. It was shown that DPV is a very sensitive and selective method for determination of total CGAs content in coffee.

On-line monitoring of in-vitro oral bioaccessibility tests as front-end to liquid chromatography for determination of chlorogenic acid isomers in dietary supplements

A novel fully automated in-vitro oral dissolution test assay as a front-end to liquid chromatography has been developed and validated for on-line chemical profiling and monitoring of temporal release profiles of three caffeoylquinic acid (CQA) isomers, namely, 3-CQA,4-CQA and 5-CQA, known as chlorogenic acids, in dietary supplements. Tangential-flow filtration is harnessed as a sample processing approach for on-line handling of CQA containing extracts of hard gelatin capsules and introduction of protein-free samples into the liquid chromatograph. Oral bioaccessibility/dissolution test assays were performed at 37.0±0.5°C as per US Pharmacopeia recommendations using pepsin with activity of ca. 749,000 USP units/L in 0.1mol/L HCl as the extraction medium and a paddle apparatus stirred at 50rpm. CQA release rates and steady-state dissolution conditions were determined accurately by fitting the chromatographic datasets, namely, the average cumulative concentrations of bioaccessible pools of every individual isomer monitored during 200min, with temporal resolutions of ≥10min, to a first-order dissolution kinetic model. Distinct solid-to-liquid phase ratios in the mimicry of physiological extraction conditions were assessed. Relative standard deviations for intra-day repeatability and inter-day intermediate precision of 5-CQA within the 5–40µg/mL concentration range were <3.4% and <5.5%, respectively. Trueness of the automatic flow method for determination of 5-CQA released from dietary supplements in gastric fluid surrogate was demonstrated by spike recoveries, spanning from 91.5–104.0%, upon completion of the dissolution process. The proposed hyphenated setup was resorted for evaluating potential differences in dissolution profiles and content of the three most abundant chlorogenic acid isomers in dietary supplements from varied manufacturers.

Role of Chlorogenic Acids in Controlling Oxidative and Inflammatory Stress Conditions

Chlorogenic acids (CGAs) are esters formed between caffeic and quinic acids, and represent an abundant group of plant polyphenols present in the human diet. CGAs have different subgroups that include caffeoylquinic, p-coumaroylquinic, and feruloyquinic acids. Results of epidemiological studies suggest that the consumption of beverages such as coffee, tea, wine, different herbal infusions, and also some fruit juices are linked to reduced risks of developing different chronic diseases. These beverages contain CGAs present in different concentrations and isomeric mixtures. The underlying mechanism(s) for specific health benefits attributed to CGAs involves mitigating oxidative stress, and hence the related adverse effects associated with an unbalanced intracellular redox state. There is also evidence to show that CGAs exhibit anti-inflammatory activities by modulating a number of important metabolic pathways. This review will focus on three specific aspects of the relevance of CGAs in coffee beverages; namely: (1) the relative composition of different CGA isomers present in coffee beverages; (2) analysis of in vitro and in vivo evidence that CGAs and individual isomers can mitigate oxidative and inflammatory stresses; and (3) description of the molecular mechanisms that have a key role in the cell signaling activity that underlines important functions.

Main iridoid glycosides and HPLC/DAD-Q-TOF-MS/MS profile of glycosides from the antioxidant extract of Eucommia ulmoides Oliver seeds

Eucommia ulmoides Oliver, a commercial tree widely in China, has long been used in traditional Chinese medicine, yet few phytochemical investigations on the seeds have been reported. The aim of the present research is to systematically isolate and identify glycosides from the antioxidant extract of E. ulmoides seeds. Antioxidant activity of each extract was evaluated by DPPH and ABTS methods based on free radical scavenging. DPPH and ABTS tests showed that the ethanol extract and each extractive fraction had strong antioxidant effects, of which ethyl acetate and n-butanol fraction showed more significant antioxidant activities with IC50 values at 87.14±0.08, 66.30±0.06μg/mL by DPPH assay and 139.61±0.05, 231.35±1.03μg/mL by ABTS test respectively. Four main iridoid glycosides were isolated firstly and structurally determined by NMR and mass spectrum data and their antioxidant effects were measured. Then other minor compounds in antioxidant extract were identified by HPLC/DAD-Q-TOF-MS/MS, totally nineteen compounds were tentatively identified by their chromatographic behaviors and mass spectral characteristics, which included ten iridoid glycosides, seven flavonoid glycosides and two chlorogenic acid isomers. Three iridoid glycoside polymers (14, 15 and 18) were tentatively identified as new compounds and compounds 5, 9 and 12 were reported in the E. ulmoides seeds for the first time. Thus, the extract and iridoid glycosides of E. ulmoides seeds had strong antioxidant effects and also had the potential commercialization for pharmaceutical and nutraceutical purposes.

Species- and cultivar-dependent traits of Prunus avium and Prunus cerasus polyphenols

In this work, we compared the patterns of polyphenol components from five varieties of cherries belonging to the family of Prunus avium (sweet cherry, 3 cultivars) and Prunus cerasus (tart cherry, 2 cultivars). The total phenol content was determined by the Folin–Ciocalteu method and the in vitro antioxidant activity by the ORAC and ABTS assays. Colorless polyphenols and anthocyanins were characterized by reversed phase-HPLC-diode array detection (DAD) and mass spectrometry (MS) combined techniques, including MALDI-TOF MS and nano-HPLC-ESI-Q-TOF-MS/MS. The polyphenol profiles were dominated by chlorogenic acid isomers and quercetin glycosides, though they substantially differed from each other. Interestingly, kaempferol-3-O-rutinoside exclusively marked the P. cerasus varieties. In all the samples, the most abundant anthocyanins were cyanidin (Cy) derivatives, mainly Cy-3-O-glucosylrutinoside, whereas Cy-3-O-xylosylrutinoside was exclusively found in tart cherries. The characteristic expression of branched tri-glycosides supports the taxonomic lineage of P. cerasus as an interspecific hybrid of P. avium and probably P. fruticosa. The anthocyanin profiles appeared both species- and cultivar-specific. Thus, after opportune validation over a larger number of varieties and biological replicates, the anthocyanin composition has potential to be exploited for classification purposes and for tracing back the cherry biotype in processed products (e.g. cherry juice, jam, flavored yogurt).

Spent coffee ground extract suppresses ultraviolet B-induced photoaging in hairless mice

The aim of this study is to evaluate the effect of spent coffee ground (SCG) ethanol extract on UVB-induced skin aging in hairless mice. An ethanol extract of SCG (ESCG) was prepared using the residue remaining after extraction of oil from roasted SCG. High performance liquid chromatography (HPLC) analysis showed that the content of caffeine (41.58±0.54μg/mg) was higher than that of chlorogenic acid isomers (~9.17μg/mg) in ESCG. ESCG significantly decreased the UVB-induced intracellular reactive oxygen species in HaCaT cells. UVB-induced wrinkle formation in mice dorsal skin was effectively reduced by ESCG administration; high dose of ESCG (5g/L) caused the reduction of wrinkle area by 30% compared with UVB-treated control (UVBC). This result correlated with the ESCG-mediated decrease in epidermis thickness (25%). In addition, ESCG administration significantly reduced transdermal water loss (20%) and erythema formation (35%) derived from UVB exposure. Collagen type I (COL-1) level in dorsal skin was effectively recovered by ESCG administration. These results were supported by down-regulation of collagen-degrading matrix metalloproteinase 2 (MMP2) and 9 (MMP9) expressions. Our results indicate that ESCG protects mouse skin from UVB-induced photoaging by suppressing the expression of matrix metalloproteinases. Our study suggests that ESCG may be anti-photoaging agent.

PHENOLIC COMPOUNDS OF WATER-ETHANOLIC EXTRACT OF MENTHA LONGIFOLIA L

The article represents data about qualitative and quantitative composition of phenolic compounds in water-ethanol extract of perspective clone of Mentha longifolia L. of NBE-NSC selection. Phenolic substances content in water-ethanol extract amounted to 3003.3 mg/100g. 13 components were determined in the extract. The extract contains caffeic acid, chlorogenic acid isomers, rosmarinic acid and glycosides of luteolin. Rosmarinic acid (50.2%) prevails among phenolic substances of Mentha longifolia extract. The conclusion is that the use of this extract is possible to create products with high biological value

Accelerated maturation of processed yerba-mate under the controlled conditions of temperature and humidity

Purpose – The purpose of this paper was to assess the changes in secondary metabolites and color during yerba-mate aging under controlled conditions. In Uruguay and Paraguay, the yerba-mate matured, in which chlorophyll degradation occurs, is preferred. For the matured product, the yerba-mate is stored for six months to one year. Design/methodology/approach – Processed yerba-mate was submitted to 35°C and 80 per cent humidity during 42 days in a climatic chamber. Samples were collected every seven days, and the phenolic compounds/methylxanthines were quantified by ultra-performance liquid chromatography – photodiode array and chlorophylls/phaeophytins by spectrophotometry. L*, a* and b* colorimetric coordinates were measured. Findings – The most expressive changes in the color occur in the first 14 days. At this time, 23.161 ± 2.984 per cent of total chlorophyll was degraded, considering that in 42 days, 37.458 ± 0.955 per cent is degraded, according to an exponential model. A positive correlation between theobromine amount and maturation time was found. This was verified by an increase in dicaffeoylquinic acid concentrations and small changes in chlorogenic acid isomers. Practical implications – The results indicate that this is a viable accelerated yerba-mate maturation process according to economics and nutraceutics. Originality/value – The paper has reported here a novel strategy to promote the yerba-mate maturation using controlled conditions.

Instant coffee extract with high chlorogenic acids content inhibits hepatic G-6-Pase in vitro, but does not reduce the glycaemia.

Coffee is the main source of chlorogenic acid in the human diet, and it contains several chlorogenic acid isomers, of which the 5-caffeoylquinic acid (5-CQA) is the predominant isomer. Because there are no available data about the action of chlorogenic acids from instant coffee on hepatic glucose-6-phosphatase (G-6-Pase) activity and blood glucose levels, these effects were investigated in rats. The changes on G-6-Pase activity and liver glucose output induced by 5-CQA were also investigated. Instant coffee extract with high chlorogenic acids content (37.8%) inhibited (p < 0.05) the G-6-Pase activity of the hepatocyte microsomal fraction in a dose-dependent way (up to 53), but IV administration of this extract did not change the glycaemia (p > 0.05). Similarly, 5-CQA (1 mM) reduced (p < 0.05) the activity of microsomal G-6-Pase by about 40%, but had no effect (p > 0.05) on glucose output arising from glycogenolysis in liver perfusion. It was concluded that instant coffee extract with high content of chlorogenic acids inhibited hepatic G-6-Pase in vitro, but failed to reduce the glycaemia probably because the coffee chlorogenic acids did not reach enough levels within the hepatocytes to inhibit the G-6-Pase and reduce the liver glucose output.

(1S,3R,4S,5R)5-O-Caffeoylquinic acid: Isolation, stereo-structure characterization and biological activity

Sorbus domestica fruits (sorbs) are commonly harvested and consumed for their nutritious qualities and have long been used as natural remedy against diabetes in the popular medicine. Recently, sorbs have been described as sources of antioxidant compounds including polyphenols. Chemical analyses carried out on sorbs collected in Southern Italy have led to the isolation of a chlorogenic acid isomer as the main antioxidant compound contained in the fruit butanol extract. NMR studies have identified the isolated compound as (1S,3R,4S,5R)5-O-Caffeoylquinic acid. In comparison to chlorogenic acid, the isolated isomer features an inverted configuration at C4. Such configurational inversion causes the chlorogenic acid stereoisomer acid to assume a preferential conformation remarkably different from that of chlorogenic acid. This seems to account for the enhanced potency of (1S,3R,4S,5R)5-O-Caffeoylquinic acid to reduce both the glucose and cholesterol uptakes by the cell line HepG2 when compared to chlorogenic acid.

Concentration of hinokinin, phenolic acids and flavonols in leaves and stems of Hydrocotyle leucocephala is differently influenced by PAR and ecologically relevant UV-B level

We examined the effects of ambient, non-stressing ultraviolet (UV)-B (280–315nm) level combined with different intensities of photosynthetic active radiation (PAR, 400–700nm) on the accumulation of the lignan (−)-hinokinin, in leaves and stems of Hydrocotyle leucocephala. Plants were exposed in sun simulators under almost natural irradiance and climatic conditions to one of four light regimes, i.e. two PAR intensities (906 and 516μmolm−2s−1) including or excluding UV-B radiation (0 and 0.4Wm−2). Besides hinokinin, we identified three chlorogenic acid isomers, one other phenolic acid, 12 quercetin, and five kaempferol derivatives in the H. leucocephala extracts. Hinokinin was most abundant in the stems, and its accumulation was slightly enhanced under UV-B exposure. We therefore assume that hinokinin contributes to cell wall stabilization and consequently to a higher resistance of the plant to environmental factors. Quercetin derivatives increasingly accumulated under UV-B and high PAR exposure at the expense of kaempferols and chlorogenic acids, which was apparently related to its ability to scavenge reactive oxygen species. In general, the concentration of the constituents depended on the plant organ, the leaf age, the light regimes, and the duration of exposure. The distribution pattern of the compounds within the examined organs was not influenced by the treatments. Based on the chemical composition of the extracts a principal component analysis (PCA) enabled a clear separation of the plant organs and harvesting dates. Younger leaves mostly contained higher phenylpropanoid concentrations than older leaves. Nevertheless, more pronounced effects of the light regimes were detected in older leaves. As assessed, in many cases the individual compounds responded differently to the PAR/UV-B combinations, even within the same phenylpropanoid class. Since this is the first report on the influence of light conditions on the accumulation of lignans in herbaceous plants, it opens many perspectives for a more precise elucidation of all involved biochemical and molecular processes.

Plants as biofactories: Stress-induced production of chlorogenic acid isomers in potato tubers as affected by wounding intensity and storage time

In the present study, the feasibility of using wounded-potato tubers as biofactories of antioxidant phenolic compounds (PC) was evaluated. Potato tubers were wounded to obtain different wounding intensities (slices, pie-cuts, and shreds) and stored for 144h at 10°C. The accumulation of total and individual PC was determined during storage of the wounded-tissue. Results indicated that the highest accumulation of total PC was obtained at 96h of storage for slices and pie-cuts. At this storage time, slices and pie-cuts showed 100% and 65% higher total PC content, respectively, whereas shredded-potatoes showed 40% lower PC content as compared with wholes before storage. The main PCs identified in wounded-potatoes were chlorogenic acid (CGA), neo-chlorogenic acid (neo-CGA), and crypto-chlorogenic acid (crypto-CGA). Results also indicated that selecting the wounding intensity to apply and storage time could manipulate the accumulation of specific PC in potato tubers. For instance, if the production of CGA or crypto-CGA were desirable, potato tubers should be wounded to obtain slices and pie-cuts. Likewise, to produce neo-CGA the appropriate wounding intensity should be pie-cuts. Furthermore, the highest accumulation of CGA and neo-CGA in wounded-potatoes was obtained at 96h of storage, whereas for the crypto-CGA its highest accumulation was observed in wounded-potatoes stored for 144h at 10°C. The stressed-potato tubers with increased concentrations of chlorogenic acids could be used as a starting material for the extraction of high value antioxidant PC with potential applications in the pharmaceutical and dietary supplements industries.