Distribution of caffeic acid derivatives in Gundelia tournefortii L.

The caffeic acid derivatives including neochlorogenic acid (3-COA), cryptochlorogenic acid (4-CQA), chlorogenic acid (5-CQA) and caffeic acid (CA) have been characterised in Gundelia tournefortii using reference compounds, chemical, spectral evidences and chromatographic data. In addition, the total phenolic content and chlorogenic acid were measured in the leaf, hull-less seed, and skin extracts of this herb by the Folin–Ciocalteu reagent and high performance liquid chromatography (HPLC), respectively. The sample analysis was carried out on a C₁₈ column with 5% (v/v) aqueous acetic acid and methanol as the mobile phase, under gradient elution at ambient temperature, at 325 nm. The amount of chlorogenic acid in the leafs (at the flowering stage and after it) and hull-less seed were 984, 466 and 199 mg per 100 g dry plant sample and the total phenolic content in their dry extract were 128.4, 103.8 and 76.3 μg/mg as CGA equivalent, respectively.     

Determination of free α-lipoic acid in foodstuffs by HPLC coupled with CEAD and ESI-MS

A simple and rapid method for determination of free α-lipoic acid in different food matrices has been developed. It consists of extraction of α-lipoic acid with 0.5% glacial acetic acid in methanol by sonication, quantitative analysis of the extract by isocratic RP-HPLC (acetonitrile/methanol/50 mM potassium dihydrogen phosphate buffer adjusted to pH 3 with phosphoric acid: 350/65/585, v:v:v) at a flow rate of 0.45 ml/min coupled with coulometric electrode array detection at potentials between +300 and +700 mV and qualitative analysis by LC–ESI-MS in the negative ion mode for confirmation. Egg, dried egg powder, mayonnaise, fine peas and potatoes were analysed and free α-lipoic acid contents ranged from 0.1 to 4.2 μg/g with recoveries between 70% and 94%. Limits of quantitation were between 0.1 and 0.3 μg/g. This newly developed method can be used to establish a database for the content of free α-lipoic acid in different foodstuffs.     

Chlorogenic acid and caffeine contents in various commercial brewed coffees

Twelve commercial brewed coffees (seven regular and five decaffeinated) were analyzed for chlorogenic acids (CGA) and caffeine by HPLC. Their pH and UV–Vis absorbances were also measured. The CGAs identified were three caffeolylquinic acids (3-CQA, 4-CQA, and 5-CQA), three feruloylquinic acids (3-FQA, 4-FQA, and 5-FQA), and three dicaffeoylquinic acids (3,4-diCQA, 3,5-diCQA, and 4,5-diCQA). The total CGAs ranged from 5.26 mg/g to 17.1 mg/g in regular coffees and from 2.10 mg/g to 16.1 mg/g in decaffeinated coffees. Among CGA, 5-CQA was present at the highest level, ranging from 2.13 mg/g to 7.06 mg/g coffee, and comprising 36–42% and 37–39% of the total CGA in the regular and decaffeinated coffees, respectively. CGA isomer contents were, in decreasing order, 5-CQA > 4-CQA > 3-CQA > 5-FQA > 4-FQA > 3-FQA > 3,4-diCQA > 4,5-diCQA, 3,5-diCQA. The caffeine content in regular and decaffeinated coffees ranged from 10.9 mg/g to 16.5 mg/g and from 0.34 mg/g to 0.47 mg/g, respectively. The pH of regular and decaffeinated coffees ranged from 4.95 to 5.99 and from 5.14 to 5.80, respectively. The relationship between the pH and the UV–Vis absorbance at 325 nm was moderately correlated (R² = 0.7829, p < 0.001, n = 12).     

Development of a simple capillary electrophoretic determination of glucosamine in nutritional supplements using in-capillary derivatisation with o-phthalaldehyde

A simple capillary electrophoretic method was developed for the determination of glucosamine using in-capillary derivatisation. Glucosamine in commercial products was extracted with purified water. The CE separation was achieved on an uncoated fused-silica capillary using a 20 mM borate buffer (pH 9.2) containing 5 mM o-phthalaldehyde (OPA) and 5 mM 3-mercaptopropionic acid (MPA) at 25 kV, followed by UV detection at 340 nm. The detector response was linear (r² > 0.999) in the concentration range 10–1000 μg/mL. The limit of detection (LOD) was 1.3 mg/g. Spiked glucosamine recoveries at 50 and 100 mg/g level were 95.1% and 104.3%, respectively. The method was applied to 16 commercial products. The concentrations of glucosamine were 109–705 mg/g, and the ratios of detected glucosamine content to the labelled value were 88.8–124%. No significant bias was observed (r² = 0.989, p < 0.01), between results obtained by the proposed CE method and an official colorimetric method (Japanese Health Food & Nutrition Food Association).     

UPLC and HPLC of caffeoyl esters in wild and cultivated Arctium lappa L.

Analytical methods including ultra-performance liquid chromatography (UPLC) and high-performance liquid chromatography (HPLC) with photodiode array (PDA) detector were developed for the analysis of caffeoylquinic acid derivatives in seeds, leaves and roots of Arctium lappa L. Separation was performed on C₁₈ column utilising 5% (v/v) acetic acid in water and acetonitrile at 330 nm. Both methodologies were validated in terms of linearity, precision, and recovery. The results showed that the major advantages of UPLC, over HPLC were the fast analysis, narrow peaks, high sensitivity, and reduction of solvent consumption. Subsequently the methods were applied for the identification and quantification of chlorogenic acid (5-CQA) and 1,5-dicaffeoylquinic acid (1,5-DCQA) as main compounds in samples. The total phenolic content of samples ranged from 3.93 to 14.13 g of 5-CQA equivalent/100 g dry weight (DW). There was a significant variability from 89 to 571 mg/100 g for 5-CQA and 48 to 486 mg/100 g for 1,5-DCQA in dry material.     

Determination of catechins in green tea infusions by reduced flow micellar electrokinetic chromatography

A sulfated-β-cyclodextrin (s-β-CD) modified reduced flow micellar electrokinetic chromatography (RF-MEKC) method was developed and validated for the determination of catechins in green tea. The optimal electrolyte consisted of 0.2% triethylamine, 50 mmol/L SDS and 0.8% s-β-CD (pH = 2.9), allowing baseline separation of five catechins in 4 min. The samples and standards were injected at 0.6 psi for 5 s under constant voltage of −30 kV. Sample preparation simply involved extraction of 2 g of tea with 200 mL water at 95 °C under constant stirring for 5 min. The method demonstrated excellent performance, with limits of detection (LOD) and quantification (LOQ) of 0.02–0.1 and 0.1–0.5 μg/mL, respectively, and recovery percentages of 94–101%. The method was applied to six samples of Brazilian green tea infusions. Epigallocatechin gallate (23.4–112.4 μg/mL) was the major component, followed by epigallocatechin (18.4–78.9 μg/mL), epicatechin gallate (5.6–29.6 μg/mL), epicatechin (4.6–14.5 μg/mL) and catechin (3.2–8.2 μg/mL).     

Simultaneous determination of acetoin and tetramethylpyrazine in traditional vinegars by HPLC method

A rapid and selective HPLC method was developed for the simultaneous analysis of acetoin (ACT) and tetramethylpyrazine (TMP). The chromatography was performed on a Zorbax SB-C18 column at 45 °C, with an aqueous mobile phase (1% acetic acid and 0.05% trifluoroacetic acid in water, pH 2.5)–(methanol) (45:55, v/v). The flow rate was 0.8 mL/min and UV detection wavelength was 297 nm. This method permits the simultaneous determination of ACT and TMP in fermentative foods with detection limits of 5.625 and 0.033 μg/mL, respectively. The recovery was 96.03% for ACT and 92.06% for TMP. Correlation coefficients were greater than 0.9999 for the two compounds. The linearity ranges for ACT and TMP were in the range of 0.02–20 mg/L and 0.12–80 μg/mL, respectively. The proposed method could be used for routine quality control of foods, beverages, natural products, or pharmaceuticals. Current data suggest that the content of TMP in vinegars is positively correlated with that of ACT.     

Simultaneous determination of four phenolic components in citrus honey by high performance liquid chromatography using electrochemical detection

A sensitive and accurate method for simultaneous separation and determination of four phenolic compounds, including caffeic acid, p-coumaric acid, ferulic acid, and hesperetin in Chinese citrus honey by high performance liquid chromatography using electrochemical detection (HPLC-ECD) has been established. Chromatographic separation was performed using a reversed phase column and methanol/4% (v/v) aqueous acetic acid as the mobile phase. The detection and quantification limits of the four compounds with ECD were 6–14 times greater than those obtained with diode-array detection (DAD). All calibration curves of the four phenolic compounds showed good linearity (r ? 0.9994) within the test ranges, 1.10–66 μg/ml, 0.35–70 μg/ml, 0.16–16 μg/ml and 0.03–10 μg/ml, respectively. The recoveries ranged from 98.9% to 100.3%. The extraction process was very simple, because of the dissolution of honey only involving water. Taken together, the application of ECD in honey determination leads to a significant improvement in the quantification of phenolic compounds, whereby paying the way for the establishment of a better quality control of citrus honey.     

The effect of processing on chlorogenic acid content of commercially available coffee

Chlorogenic acids (CGA) are a class of polyphenols noted for their health benefits. These compounds were identified and quantified, using LC–MS and HPLC, in commercially available coffees which varied in processing conditions. Analysis of ground and instant coffees indicated the presence of caffeoylquinic acids (CQA), feruloylquinic acids (FQA) and dicaffeoylquinic acids (diCQA) in all 18 samples tested. 5-CQA was present at the highest levels, between 25 and 30% of total CGA; subsequent relative quantities were: 4-CQA > 3-CQA > 5-FQA > 4-FQA > diCQA (sum of 3,4, 3,5 and 4,5-diCQA). CGA content varied greatly (27.33–121.25 mg/200 ml coffee brew), driven primarily by the degree of coffee bean roasting (a high amount of roasting had a detrimental effect on CGA content). These results highlight the broad range of CGA quantity in commercial coffee and demonstrate that coffee choice is important in delivering optimum CGA intake to consumers.     

Acrylamide in espresso coffee: Influence of species,roast degree and brew length

Espresso coffees were analysed for acrylamide contents by matrix solid-phase dispersion and GC–MS. The influence of coffee species, roast degree, and brew length were ascertained. Mean acrylamide contents of medium roasted espressos (30 mL) were 1.16 ± 0.25 and 2.31 ± 0.43 μg for pure arabica and robusta samples, respectively. Espressos prepared from commercial blends contained an average acrylamide level of 1.26 ± 0.28 μg. A 25% decrease was observed when comparing espressos prepared with medium and dark roasted coffee. The extraction efficacy of acrylamide for standard espressos of 30 mL was near 80%, being only affected by brew volume, with long espressos (70 mL) containing practically all acrylamide of the coffee cake (99%), almost double that of short ones (20 mL). When compared with other common coffee beverages, espresso acrylamide concentration (μg/L) was higher. However, due to the small volume per cup, it may contribute less to acrylamide ingestion.     

Development and validation of an HPLC-method for determination of free and bound phenolic acids in cereals after solid-phase extraction

Whole cereal grains are a good source of phenolic acids associated with reduced risk of chronic diseases. This paper reports the development and validation of a high-performance liquid chromatography–diode array detection (HPLC–DAD) method for the determination of phenolic acids in cereals in either free or bound form. Extraction of free phenolic acids and clean-up was performed by an optimised solid-phase extraction (SPE) protocol on Oasis HLB cartridges using aqueous methanol as eluant. The mean recovery of analytes ranged between 84% and 106%. Bound phenolic acids were extracted using alkaline hydrolysis with mean recoveries of 80–95%, except for gallic acid, caffeic acid and protocatechuic acid. Both free and bound phenolic extracts were separated on a Nucleosil 100 C₁₈ column, 5 μm (250 mm × 4.6 mm) thermostated at 30 °C, using a linear gradient elution system consisting of 1% (v/v) acetic acid in methanol. Method validation was performed by means of linearity, accuracy, intra-day and inter-day precision and sensitivity. Detection limits ranged between 0.13 and 0.18 μg/g. The method was applied to the analysis of free and bound phenolic acids contents in durum wheat, bread wheat, barley, oat, rice, rye, corn and triticale.     

Simplified extraction of tetracycline antibiotics from milk using a centrifugal ultrafiltration device

A simplified method was developed for the simultaneous determination of oxytetracycline, tetracycline, chlortetracycline, and doxycycline in milk. Isolation of the target compounds was performed using an Ultrafree-MC/PL centrifugal ultrafiltration device without prior sample preparation. Analyses were carried out via high-performance liquid chromatography using a Discovery HS F5 column with a gradient mobile phase which consisted of 30 mM citric acid solution (pH 3, in water) and acetonitrile (60:40 → 40:60, v/v). Recovery of the target compounds from spiked samples at four levels (0.05, 0.1, 0.2, and 0.5 μg/mL) was higher than 87%, with relative standard deviations of less than 6%. Limits of quantification ranged from 0.01 to 0.04 μg/mL.     

Determination of carnosic acid and rosmarinic acid in sage by capillary electrophoresis

A simple and rapid capillary electrophoresis method was developed for the identification and quantitative determination of two antioxidative compounds – carnosic acid and rosmarinic acid – in the extracts of commercial Sage (Salvia officinalis) tea-bags. Capillary zone electrophoretic separation of carnosic and rosmarinic acids was performed using 40 mmol/l borate, at pH 9.6 as the running buffer. Weighed sage samples were extracted from tea-bags by sonification and the extracts were directly injected without any purification and pre-separation process. Coumarin was used as internal standard for quantitation and the limits of detection for carnosic acid and rosmarinic acid were obtained as 2.79 and 3.18 μg/ml, respectively using UV detection at 210 nm.     

Inhibitory effects of chlorogenic acids from green coffee beans and cinnamate derivatives on the activity of porcine pancreas α-amylase isozyme I

Nine kinds of chlorogenic acids (CGAs) account for 80% of the total CGA content in green coffee beans. They consist of three subgroups of caffeoylquinic acids (CQAs), feruloylquinic acids (FQAs), and dicaffeoylquinic acids (diCQAs). We previously reported the inhibitory effects of 5-CQA on porcine pancreas α-amylase (PPA) isozymes, PPA-I and PPA-II. In this paper, we investigated the PPA-I inhibition by eight kinds of CGAs. The IC₅₀ values of CQAs, FQAs, and diCQAs against the PPA-I-catalysed hydrolysis of p-nitrophenyl-α-D-maltoside were 0.08–0.23 mM, 1.09–2.55 mM, and 0.02–0.03 mM, respectively. All CQAs and FQAs and 3,5-diCQA showed mixed-type inhibition with binding to the enzyme–substrate complex (ES) being stronger than to the enzyme (E). 3,4-DiCQA and 4,5-diCQA showed mixed-type inhibition, but, conversely are suggested to bind to E stronger than ES.     

Ultrasound-assisted hydrolysis and gas chromatography–mass spectrometric determination of phenolic compounds in cranberry products

An ultrasound-assisted hydrolysis and gas chromatography–mass spectrometric (GC–MS) method has been developed for determination of phenolics in cranberry products. Prior to GC–MS separation and characterisation, the phenolics in samples were hydrolysed by hydrochloric acid with ultrasound-assistance, extracted with ethyl acetate, and derivatised with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) + 1% trimethylchlorosilane (TMCS) reagents. The application of ultrasonication significantly accelerated the acidic hydrolysation of the conjugated phenolics. A baseline separation of the 20 phenolics and internal standard was achieved in 25 min. Standard calibration curves were linear over the concentration range of 0.0–50 μg/mL and detection limits were 0.06–0.70 μg/mL. Twenty phenolics were identified in cranberry samples and all of them occurred mainly in conjugated forms. Of those, the benzoic acid, quercetin, and myricetin were most abundant phenolics. The total phenolics were 12.4 mg/g in cranberry fruits, 9.1 mg/mL in 100% cranberry juice, and 11.1 mg/g in cranberry sauces, respectively.     

Investigation of folic acid stability in fortified instant Asian noodles by use of capillary electrophoresis

A simple, rapid procedure, using capillary zone electrophoresis (CZE), that can efficiently measure added folic acid in fortified instant fried noodles has been developed and validated. Optimum separation of folic acid was obtained on a 72 cm × 75 μm capillary using 8 mM phosphate-12 mM borate run buffer with 5% MeOH at pH 9.5, temperature of 30 °C and voltage of 28 kV. The extracts were introduced into the capillary via electrokinetic injection and the folic acid monitored at 214 nm. For quantification purposes, nicotinic acid was added as internal standard to all samples. Under these conditions the analysis required approximately 12 min. Good results were obtained for different analytical parameters including linearity, accuracy and precision. The limit of detection was calculated to be 5.3 mg/L. Prior to CZE determination, noodle samples were homogenized in the buffer solution for 1 h followed by treatment with α-amylase solution for 1 h at 65 °C or protease solution for 4 h at 37 °C. The enzyme solution was added at a concentration of 25 mg/L and then adjusted to pH 7.0. Using standard addition to eliminate the effect of sample matrix interference, results showed that a higher and more efficient recovery of added folic acid could be obtained when using α-amylase. During the four main stages of instant fried noodle manufacturing (dough crumbs, cut sheets, steaming and frying) folic acid was found to be stable with recoveries of 96–103%.     

Microwave-assisted extraction and determination of cyanuric acid residue in infant formula samples by liquid chromatography–tandem mass spectrometry

In the present work, microwave-assisted extraction method in combining with liquid chromatography–tandem mass spectrometry (LC–MS/MS) was proposed for the determination of cyanuric acid (CYA) in infant formula samples. The separation was performed on a MERCK ZIC HILIC column (150 × 2.1 mm i.d., 5 μm) with gradient elution of 20 mM ammonium acetate solution – acetonitrile. The method could respond linearly with cyanuric acid at concentrations from 1.0 to 50 ng mL⁻¹ with a quantification limit of 0.25 mg kg⁻¹. The intra- and inter-day precision was less than 4% and the recovery of the assay was in the range of 86.7–93.1%. In the analysis of practical spiked infant formula samples, the new method yielded satisfactory results. Due to its simplicity and accuracy the straightforward method is particularly suitable for routine cyanuric acid detection.     

Determination of capsaicin and dihydrocapsaicin in Capsicum anuum and related products by capillary electrophoresis with a mixed surfactant system

An easy, rapid, sensitive, and cheap capillary electrophoresis (CE) method based a mixed surfactant system formed by sodium dodecyl sulphate (SDS) and polyoxyethylene sorbitan monolaurate (Tween 20) as modifier in the buffer was reported. Quantitative analysis of capsaicin and dihydrocapsaicin in Capsicum anuum, pepper sauce and porous capsicum plaster was demonstrated. After conducting a series of optimisations, baseline separation was obtained for the analytes within 5 min under the optimum conditions (15 mM sodium tetraborate–0.05% (v/v) Tween 20–2.2 mM SDS buffer (pH 10.1), 20 kV voltage, 214 nm UV detection). The method resulted in excellent linearity, with r² of regression equation of 0.9994 and 0.9996 for capsaicin and dihydrocapsaicin, respectively. Recoveries were in the range 90–107% and 92–109% for capsaicin and dihydrocapsaicin, respectively.     

5-Hydroxymethylfurfural content in foodstuffs determined by micellar electrokinetic chromatography

Micellar electrokinetic chromatography (MEKC) has been applied for the determination of 5-hydroxymethylfurfural in several foodstuffs. A 75 mM phosphate buffer solution at pH 8.0 containing 100 mM sodium dodecylsulphate was used as background electrolyte (BGE), and the separation was performed by applying +25 kV in a 50 μm I.D. uncoated fused-silica capillary. Good linearity over the range 2.5–250 mg kg⁻¹ (r² ? 0.999) and run-to-run and day-to-day precisions at low and medium concentration levels were obtained. Sample limit of detection (0.7 mg kg⁻¹) and limit of quantification (2.5 mg kg⁻¹) were established by preparing the standards in blank matrix. The procedure was validated by comparing the results with those obtained with liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS). Levels of HMF in 45 different foodstuffs such as breakfast cereals, toasts, honey, orange juice, apple juice, jam, coffee, chocolate and biscuits were determined.     

Development of a matrix solid-phase dispersion-sonication extraction method for the determination of fungicides residues in ginseng extract

A rapid method based on matrix solid-phase dispersion (MSPD) was developed for the determination of pentachloronitrobenzene, pentachloroaniline, methylpentachloro-phenylsulphide and procymidone in ginseng extract using gas chromatography. The optimal conditions selected for MSPD extraction were as follows: after blending 5 mL of aqueous ginseng extract (10%, w/v) with Florisil (10 g), the mixture was passed into a small chromatographic column and extracted twice with 10 mL ethyl acetate–hexane solvent mixture (70:30, v/v) for 15 min in an ultrasonic bath at room temperature. The analytical performance of this method showed MSPD to be efficient, fast, simple and had little or no matrix effect. The method detection limits varied from 0.1 to 0.4 μg/L. Mean recoveries were found in the range of 83.5–97.4% and had a good linear relationship (r² ? 0.9987) with relative standard deviations less than 10%. The proposed method has proved to be a feasible one for the analysis of fungicide residues in ginseng extract.