[show abstract][hide abstract] ABSTRACT: The mineral and flavonoid contents of commercially available different types of teas (premium black, flavored black, green, and fruit tea) and the infusions produced from them were determined. Studied teas differed in the contents of elements between their raw materials and infusions. Iron and copper exhibited the lowest efficiency of extraction by hot water. For the most popular black tea brand (Lipton® Yellow label) the efficiency of metal extraction decreased in the order: Co>Mn>Ni>Zn>Cu>Fe. Flavored black Citrus tea infusion had the highest content of Co and Ni, while Yellow label and Green Indonesia are a good source of Fe, Mn, and Zn. Flavonoids were predominantly present as glycosides. Rutin was present at much higher levels in black and green teas. Significant amounts of naringin and hesperidin were determined in tea infusions with citrus aromas or fruits.
Food science and biotechnology 08/2013; 22(4). · 0.70 Impact Factor
[show abstract][hide abstract] ABSTRACT: The hydrophilic interaction chromatography (HILIC) coupled to mass spectrometry was employed to study retention behavior of several flavonoids from their different groups using the polymeric zwitterionic stationary phase (ZIC-pHILIC). It contains sulfobetaine-bonded ligand with an inner positively charged quaternary ammonium and an outer negatively charged sulfonate functional groups. Two organic solvents – acetonitrile (ACN) and methanol (MeOH) – were compared as a component of mobile phase. Separation parameters such as a content of organic modifier, pH of an eluent and a column temperature were studied. Retention of flavonoids is controlled primarily by a partition between the mobile phase eluent and a water-enriched layer on the hydrophilic stationary phase with some contribution from hydrogen bonding formation. Using MeOH, in contrast to ACN, strongly retained compounds (myricetin, morin, rutin and quercetrin) could be eluted under isocratic conditions. A better sensitivity was achieved with MeOH as mobile phase component, particularly for quercetin, naringenin and kaempferol. The method was applied to the determination of flavonoids in fruit juices.
[show abstract][hide abstract] ABSTRACT: Chilli CM334 (Capsicum annuum L.) is resistant to Phytophthora capsici Leonian (Pc), but Nacobbus aberrans Thorne and Allen, 1944 (Na) broke down its resistance in plants previously infected by the nematode. Peroxidase (POD) and L-phenylalanine ammonia-lyase
(PAL) activity, total soluble phenols (TSP) and chlorogenic acid concentration in CM334 plants inoculated with either or both
pathogens (Na-Pc) were compared; also, the toxic effect of some phenolic acids on Na was tested in vitro. The highest POD activity (5.3μM tetraguaiacol mg−1 protein min−1) was registered in plants inoculated only with Pc, while those inoculated only with Na showed the lowest (3.3μM) (P ≤ 0.05). PAL activity was 39.9nM trans-cinnamic acid μg−1 protein min−1 in plants inoculated only with Pc, and it was lower (19.3nM) and similar in non-inoculated plants or those with Na and with Na-Pc (P ≤ 0.05). Usually, plants inoculated with Pc alone had higher contents of TSP (P ≤ 0.05) (1.9mg tannic acid g−1 dry matter) and plants inoculated with Na or Na-Pc had lower levels (0.8 and 0.9mg) than those non-inoculated (1.3mg). CM334 plants inoculated with Na showed a significant reduction (10–37% and 12–17%, in roots and leaves) in the concentration of chlorogenic acid as compared
to the non-inoculated. Vanillic, trans-cinnamic, p-coumaric and syringic acids had greater nematicidal effects (P ≤ 0.05) than chlorogenic acid in vitro. Apparently Na modified the defence responses in CM334 plants as POD and PAL activities and TSP and chlorogenic acid concentrations were
KeywordsChlorogenic acid-PAL-Peroxidase-Plant defences-Resistance breaking-Root-knot nematodes
Plant and Soil 04/2012; 338(1):399-409. · 2.64 Impact Factor
[show abstract][hide abstract] ABSTRACT: The optimum conditions for extraction of rutin and quercetin from Hypericum perforatum were investigated. The best efficiency of extraction was achieved with aqueous methanol 40–80% (v/v). For quercetin analysis as aglycone the effect of acid concentration and hydrolysis time on the extraction recovery were
also studied. Hydrolysis for 5min in the presence of 2.8molL−1 HCl as well as for 10min with 1.1molL−1 HCl efficiently released quercetin from rutin. The content of quercetin−3-O-glycosides (rutin, hyperoside and quercetrin) and quercetin aglycone as well as chlorogenic and caffeic acids in H. perforatum leaves and flowers were determined by HPLC with photodiode-array detection and confirmed by electrospray mass spectrometry.
[show abstract][hide abstract] ABSTRACT: Aromatised green teas are widely sold and popular owing to their fragrance. In this study the antioxidant activity of six commercial green tea infusions was assessed by three complementary assays.
In order to evaluate the tea infusions as antioxidant sources, their phenolic content (Folin-Ciocalteu assay), cupric ion-reducing antioxidant capacity (CUPRAC) and 2,2-diphenyl-1-picryhydrazyl (DPPH) radical-scavenging ability were determined. Their content of polyphenols was also determined by high-performance liquid chromatography/mass spectrometry (HPLC/MS) in negative electrospray ionisation mode. Some teas with citrus aroma, besides having a relatively high content of catechins, also contain other phenolic compounds such as naringin and hesperidin. The three assays used to evaluate the antioxidant capacity of the tea infusions gave different rank orders. Therefore an antioxidant index was calculated for better correlation of the results, and its highest value was obtained for Clear Green Mint tea infusion.
The studied teas, besides having a relatively high content of catechins, also contain naringin and hesperidin, which are not present in 'pure' green tea. It is important to run multiple assays to get a better estimate of the antioxidant capacity of a given sample.
Journal of the Science of Food and Agriculture 02/2012; 92(11):2244-9. · 1.76 Impact Factor
[show abstract][hide abstract] ABSTRACT: The content of selected flavonoids and phenolic acids of 12 commercial flavoured black tea infusions was determined by high-performance liquid chromatography with tandem mass spectrometry in the negative electrospray ionization mode. Assays for the evaluation of their antioxidant capacity were carried out by cupric ion reducing antioxidant capacity, Folin-Ciocalteu assay, cyclic voltammetry and potentiometry. Flavonoids were predominantly present as glycosides in the studied infusions. Only quercetin as a free aglycone was found at trace levels. Notable amount of naringin and hesperidin was determined in teas with citrus aromas or fruits. These compounds were not found in premium black tea. Two principal groups of the studied teas were found using cluster analysis in relation to the values of their antioxidant activities.
International Journal of Food Sciences and Nutrition 01/2012; 63(6):742-8. · 1.26 Impact Factor
[show abstract][hide abstract] ABSTRACT: Zwitterionic hydrophilic interaction chromatography (ZIC-HILIC) was used to study the retention of selected flavonols. In gel ZIC columns the active layer grafted on polymeric support contains both strongly acidic sulfonic acid groups and strongly basic quaternary ammonium groups in the molar ratio of 1:1, separated by a short alkyl spacer. Retention behavior of the compounds was investigated by varying the separation conditions, e.g. the kind of organic solvent in the mobile phase (acetonitrile or methanol), its ratio to water and pH value. Polar (hydrogen-bonding and dipole-dipole) interactions in the stationary phase are of primary importance, even though weak electrostatic interactions affect the separation of analytes carrying either positive or negative charges.
Current Topics in Analytial Chemsitry. 01/2012; 9:49-55.
[show abstract][hide abstract] ABSTRACT: The characterisation of micro-samples from works of art and archaeological residues is a particularly complex task, due to the fact that only a relatively low amount of material is available for sampling, and compounds both derived from the target analytes and the matrix can be simultaneously present. Thus, sensitive, selective and reliable analytical procedures need to be developed. This paper presents the optimisation of an instrumental procedure based on liquid chromatography with mass spectrometric detection, which allows for determining selected analytes (anthraquinones, tannins, flavonoids), along with their known degradation products: phenolic acids. The instrumental parameters were optimised in terms of selecting the best ionisation source (APCI and ESI were compared), choosing the compound-dependant MS parameters and enhancing selectivity and sensitivity (SIM and MRM analyses were compared). The proposed procedure proved to be sensitive and selective, with limits of detection (0.4-20 ng/mL). The analytical procedure was validated by characterising reference materials, i.e. dyed and undyed woollen and silk yarns, both freshly prepared and artificially aged. Particularly, the study focused on the determination of 4-hydroxybenzoic acid, and on the correlation between its relative amounts with respect to ageing time. The optimised procedure was also applied to historical samples and proved fundamental in unravelling the complex composition of black dyed yarns collected from a medieval tapestry. The much degraded yarns were dyed with a tannin based dye, extracted from gallnuts, alder bark or sumac; the less degraded ones were coloured by superimposing colours with cochineal, madder, weld and indigo dye baths, and eventually by adding gallo-tannins as well.
Journal of chromatography. A 08/2011; 1218(34):5837-47. · 4.19 Impact Factor
[show abstract][hide abstract] ABSTRACT: The LC-MS/MS was applied for the determination of flavonoids' stability under four types of solvent extraction methods (reflux heating, sonication, maceration and microwave) from maize samples. The 11 flavonoids belong to different groups: flavonols (kaempferol, myricetin, rhamnetin, quercetin, rutin), flavanones (naringenin, naringin, hesperedin), flavones (apigenin, luteolin), isoflavones (genistein) were studied. The effect of the degradation of flavonoids depended on extraction mode and chemical structure. The smallest decomposition was observed by heated reflux extraction procedure within 30 min in water bath and by microwave assisted extraction under 160 W during 1 min. The decomposition for flavonoids depends on number of substituents in flavonoid molecule. The most unstable compound (recovery below 50%) in tested condition was myricetin. The higher number of hydroxyl groups promote degradation of flavonoids, whereas sugar moiety and methoxyl groups protect flavonoids of degradation during microwave and ultrasonic assisted extraction.
Journal of chromatography. A 03/2011; 1218(18):2505-12. · 4.19 Impact Factor
[show abstract][hide abstract] ABSTRACT: Antioxidant properties of the water extracts of the commercial bagged fruit and flavoured black teas were evaluated and compared with typical black teas of C. sinensis.
Folin-Ciocalteu (FC) assay, cupric ion reducing antioxidant capacity (CUPRAC) and DPPH radical method were used for these purposes. The content of selected flavonoids and phenolic acids was also determined by high-performance liquid chromatography with tandem mass spectrometry in the negative electrospray ionization mode.
Flavoured black teas contain significantly higher level of catechins, quercetin, and rutin, while the content of chlorogenic and caffeic acids as well as naringin and hesperidin was higher in fruit teas. Supplementation with these flavonoids could reduce blood glucose. In FC and DPPH assays, the antioxidant properties of studied tea infusion increases in the order: fruit tea < flavoured black tea > premium black tea, while in CUPRAC method, some aromatized teas exhibit the highest antioxidant properties. Tea infusions with nice smell of fruits would also support the human diet with some source of antioxidants.
European Journal of Nutrition 03/2011; 50(8):681-8. · 3.13 Impact Factor
[show abstract][hide abstract] ABSTRACT: Quercetin, one of the most common dietary flavonols, was investigated in the presence of Cu(II) ions in methanolic solution in order to obtain some explanation on the mechanism interaction and its action against free radical-mediated damage. The spectroscopic studies (UV-VIS, IR, ESI-MS) were used to assess the extent to which it undergo complex formation through chelation or modification through oxidation. The reaction of quercetin with Cu(II) resulted in the formation of 1:1 metal-ligand complex (λ(max) = 436 nm) through the carbonyl oxygen and 3-OH group in C ring. Then quercetin is oxidized to the benzoquinone type products. The addition of EDTA destroyed the complex but did not regenerate the whole original spectrum of quercetin. From the other hand, the presence of EDTA inhibits formation of copper-quercetin complex and quercetin oxidation. The antioxidant activity of the Q + Cu solutions was evaluated by using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH∙) radical scavenging method and from an electrochemical point of view. The complex is much more effective as free radical scaveninger than the free flavonoid.
Biology of Metals 02/2011; 24(1):41-9. · 3.17 Impact Factor
[show abstract][hide abstract] ABSTRACT: An improved and simplified analytical method which offers rapid, accurate determination and identification of phenolic compounds in honey samples is reported. The honey samples were diluted by acidified water (pH 2), and analyzed by HPLC-ESI-MS/MS. Simultaneously determination of phenolic acids and flavonoids was carried out by a liquid chromatography-mass spectrometry. Comparison between atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) was performed by analysis of standards. Fragmentation of analytes for subsequent selective Multiple Reaction Monitoring (MRM) analysis was investigated in negative mode. Sample preparation without separation of sugars and clean-up procedure, followed by fast chromatographic separation using a narrow-bore column C18 (50 mm x 2.1 mm, 3 microm) allowed the analysis to be completed in a short run time. LODs were ranged between 1 and 15 ng L(-1) for p-coumaric acid and naringenin, respectively. The method was applied for determination of phenolic acids and flavonoids in honey samples from different botanical origin.
Journal of chromatography. A 09/2009; 1216(38):6620-6. · 4.19 Impact Factor
[show abstract][hide abstract] ABSTRACT: RP HPLC-UV-MS was optimized for simultaneous determination of several prominent flavonoids (quercetin, naringenin, naringin, myricetin, rutin and kaempferol) using a commercially available monolithic column and isocratic elution. The concentration of organic modifier (methanol and ACN) was tested in order to obtain the best resolution. The LODs for a UV detector at 254 nm were comprised between 0.1 microg/mL for myricetin and quercetin and 0.5 microg/mL for rutin, naringin and kaempferol with the precision in the range of 1.5-3.0% RSD. MS detection with multiply reaction monitoring (MRM) offers a considerable gain in selectivity as well as sensitivity LODs for flavonoids were in the range of 1-20 ng/mL. The developed method was used for monitoring the content of some flavonoids in tomatoes during their maturation process.
Journal of Separation Science 08/2009; 32(15-16):2835-40. · 2.59 Impact Factor
[show abstract][hide abstract] ABSTRACT: Honey is rich in phenolic acids and flavonoids, which exhibit a wide range of biological effects and act as natural antioxidants. The analysis of polyphenols has been regarded as a very promising way of studying floral and geographical origins of honeys. This review surveys recent literature on determination of these active compounds in honey. The analytical procedure to determine individual phenolic compounds involves their extraction from the sample matrix, analytical separation and quantification. We pay particular attention to sample pre-treatment and separation techniques (e.g., high-performance liquid chromatography and electrophoresis).
[show abstract][hide abstract] ABSTRACT: Quercetin and its glycosides are widely distributed in the plant kingdom and belong to the most abundant of the flavonoid molecules. Besides their important biological roles in plant pigmentation, these flavonols possess anti-cancer and anti-inflammatory properties, which are the consequence of their affinity for proteins and their anti-oxidant properties. The content of quercetin and its glycosides in different plants have been summarized in various papers, although quantitative data are not so reliable due to the wide diversity of extraction and determination procedures. The general analytical strategy involves the isolation from a sample matrix followed by separation, identification and measurement. The recovery step usually involves solvent extraction using a range of solvents. Separation is commonly achieved by high-performance liquid chromatography (HPLC) and capillary electrophoresis. This paper intends to present and discuss the analytical procedures for determination of quercetin—aglycone as well as its conjugates—in different plant materials by means of routine and more recently developed separation techniques. Selected applications are included to illustrate the scope and limitations of the various approaches.
[show abstract][hide abstract] ABSTRACT: Workers involved in the manufacture of drug substances may be exposed to active pharmaceuticals by inhalation of drug dusts or droplets which has been considered the main exposure route. The proposed HPLC method allowed to determine sulpiryde, hydroxyurea and dyprophylline in the concentration range of 0.01-0.187 mg/m3, 0.001-0.08 mg/m3 and 0.01-0.40 mg/m3 for sulpiryde, hydroxyurea and dyprophylline, respectively, when 480 L of air sample was collected on the glass fibre filters. Sulpiryde was extracted with a solvent system consisting of acetonitrile-phosphate buffer at pH 3 (85:15, v/v), while the best efficiency of extraction for hydroxyurea and dyprophylline was achieved using water. HPLC analysis of sulpiryde with fluorescence detection was more sensitive (LOD=3.1 microg/L) in comparison with UV detection (LOD=84.4 microg/L).
Journal of Biochemical and Biophysical Methods 05/2008; 70(6):1283-6. · 2.33 Impact Factor
[show abstract][hide abstract] ABSTRACT: The solid-phase extraction procedure (SPE) for isolation and preconcentration of phenolic acids (gallic, p-HBA, p-coumaric, vanillic, caffeic and syringic acid) and some flavonols (rutin, quercetin and kaempferol) from honey samples prior to their determination by HPLC is reported. Different solid sorbents such as Bond Elut octadecyl C(18), Oasis HLB, Strata-X and Amberlite XAD-2 were tested for this purpose. The best results were obtain when aqueous solution of honey (100 mL) was adjusted to pH 2 and passed through the microcolumn containing 2.5 g of Oasis HB followed by washing the sorbent with 50 mL of acidified water (pH 2). The analytes were then eluted with methanol. The proposed method permits the quantification of the studied compounds with the limit of detections ranged from 25 ng kg(-1) to 0.75 microg kg(-1) for p-HBA and quercetin, respectively. The precision of the overall analytical procedure was estimated by measuring the within-day repeatability and the relative standard deviations of the parallel (n=3) results were in the range of 1.9-10.1%. The method was tested for real honey samples from different botanical origins.
Journal of Chromatography 05/2008; 1187(1-2):18-24. · 4.61 Impact Factor
[show abstract][hide abstract] ABSTRACT: Reversed-phase HPLC was optimised for simultaneous determination of several derivatives of benzoic and hydroxycinnamic acids (so-called phenolic acids) in plums using a commercially available monolithic column. Mobile phase pH and concentration of organic modifier (methanol and acetonitrile) were tested in order to obtain the best resolution. Satisfactory separation was achieved in gradient mode with a mobile phase consisting of 50 mM phosphate buffer at pH 2.2 (solvent A) and acetonitrile (solvent B). The limits of detection for a UV detector ranged between 0.098 and 2.04 microg/mL for vanillic acid and p-hydroxyphenylacetic acid, respectively. The developed method was used for monitoring the content of polyphenolic acids in plums during their ripening process. The presence of these constituents was confirmed by checking their MS spectra.
Journal of Separation Science 12/2007; 30(17):2929-34. · 2.59 Impact Factor
[show abstract][hide abstract] ABSTRACT: Carbon nanotubes and graphitized carbon are investigated as adsorbents for solid phase extraction of dicamba and 2,4,5-T,
two phenoxyalkanoic acid herbicides. These adsorbents have much greater adsorption capability than that of C18 bonded silica, which was also tested for comparison studies. The adsorption capacity increases remarkably at lower pH of
the sample solution. Freundlich isotherms were applied to analyze the data. Our studies suggest that carbon nanotubes have
great potential applications in environmental analysis.
[show abstract][hide abstract] ABSTRACT: Quercetin is a typical flavonoid ubiquitously present in vegetables and fruits, and its antioxidant effect is implied to be helpful for human health. The efficiency of extraction process and acidic hydrolysis parameters for HPLC analysis of quercetin present in glycosides and aglycone forms was investigated. Hydrolysis for 5min in the presence of 2.8M HCl as well as for 10min with 1.1M HCl efficiently released quercetin from rutin. The method developed in this study was applied for quantitative determination of quercetin in some food (onion, apple) and herbal (Hypericum perforatum and Sambucus nigra) products.