Optimisation of the on-fibre derivatisation of volatile fatty acids in the simultaneous determination together with phenols and indoles in cow slurries

The on-fibre derivatisation of volatile fatty acids (VFAs) using N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA) was optimised in the simultaneous determination of VFAs together with phenols and indoles by headspace solid-phase microextraction (SPME)–gas chromatography–mass spectrometry. Firstly, the nature of the SPME fibre was optimised and four different fibres were studied (100 μm polydimethylsiloxane, 85 μm Carboxen/polydimethylsiloxane, 5/30 μm divinylbenzene/Carboxen/polydimethylsiloxane and 85 μm polyacrylate). The optimum fibre (50/30 μm divinylbenzene/Carboxen/polydimethylsiloxane) was used to study the exposure time of the fibre to the derivatisation agent and the desorption time and temperature. Firstly, a factorial design was built but since the three variables had a significant effect, a central composite design was used to build the response surfaces. The best signals were obtained after the exposure of the fibre in the headspace of the MTBSTFA derivatisation reagent for 1 h and desorption at 300 °C for 9 min. The determination of underivatised phenols and indoles was not affected by the presence of the derivatisation reagent in the fibre.     

Antioxidant capacity,radical scavenger activity,lipid oxidation protection analysis and antimicrobial activity of red grape extracts from different varieties cultivated in Portugal

The aim of this study was to investigate the antioxidant capacity, radical scavenger activity, lipid oxidation protection and antimicrobial activity of grape extracts from 12 different red grape varieties cultivated in Portugal. The mean values of total phenolic content quantified in grape extracts varied from 833.7 to 2005.6 mg/L gallic acid. Antioxidant capacity results showed different values for each grape variety ranging from 3.96 to 32.96 mm/L Fe(II). The scavenger activity values ranged from 15.99% to 54.82% for the superoxide radical and from 11.79% to 29.67% for the hydroxyl radical. The grape extracts with the highest antioxidant capacity had a positive effect on the lipid oxidation protection and induced low peroxide values in butter samples. Finally, concerning antimicrobial activity, grape extracts from Touriga Nacional and Tinta Roriz grape varieties had significant antimicrobial activity, especially notable for total mesophilic aerobics.     

Reduction in hypericin-induced phototoxicity by Hypericum perforatum extracts and pure compounds

Clinical evidence suggests that administration of Hypericum perforatum (Hp) extracts containing the photo-activated hypericin compounds may cause fewer skin photosensitization reactions than administration of pure hypericin. This study was conducted to determine whether the phototoxicity of hypericin in HaCaT keratinocytes could be attenuated by H. perforatum extracts and constituents. Two extracts, when supplemented with 20 microM hypericin: (1) an ethanol re-extraction of residue following a chloroform extraction (denoted ethanol(-chloroform)) (3.35 microM hypericin and 124.0 microM total flavonoids); and (2) a chloroform extract (hypericin and flavonoids not detected), showed 25% and 50% (p<0.0001) less phototoxicity than 20 microM hypericin alone. Two H. perforatum constituents, when supplemented with 20 microM hypericin: (1) 10 microM chlorogenic acid; and (2) 0.25 microM pyropheophorbide, exhibited 24% (p<0.05) and 40% (p<0.05) less phototoxicity than 20 microM hypericin alone. The peroxidation of arachidonic acid was assessed as a measure of oxidative damage by photo-activated hypericin, but this parameter of lipid peroxidation was not influenced by the extracts or constituents. However alpha-tocopherol, a known antioxidant also did not influence the amount of lipid peroxidation induced in this system. These observations indicate that hypericin combined with H. perforatum extracts or constituents may exert less phototoxicity than pure hypericin, but possibly not through a reduction in arachidonic acid peroxidation.     

GC-MS determination of parabens,triclosan and methyl triclosan in water by in situ derivatisation and stir-bar sorptive extraction

Stir-bar sorptive extraction in combination with an in situ derivatisation reaction and thermal desorption–gas chromatography–mass spectrometry was successfully applied to determine parabens (methylparaben, isopropylparaben, n-propylparaben, butylparaben and benzylparaben), triclosan and methyltriclosan in water samples. This approach improves both the extraction efficiency and the sensitivity in the GC in a simple way since the derivatisation reaction occurs at the same time as the extraction procedure. The in situ derivatisation reaction was carried out with acetic anhydride under alkaline conditions. Thermal desorption parameters (cryofocusing temperature, desorption flow, desorption time, desorption temperature) were optimised using a Box–Behnken experimental design. All the analytes gave recoveries higher than 79%, except methylparaben (22%). The method afforded detection limits between 0.64 and 4.12 ng/L, with good reproducibility and accuracy values. The feasibility of the method for the determination of analytes in water samples was checked in tap water and untreated and treated wastewater.     

Optimisation of the derivatisation reaction and subsequent headspace solid-phase microextraction method for the direct determination of chlorophenols in red wine

An acetylation reaction for the derivatisation of the three chlorophenols involved in cork taint was optimised using a Doehlert design for direct application in wine samples. In this first step, the optimum reaction pH, by adding different amounts of KHCO3, and the required quantity of derivatisation reagent were fixed. Then a series of parameters relevant for the headspace solid-phase microextraction process, such as desorption conditions, salt addition and agitation sample were evaluated. A simultaneous study of the type of fibre and extraction temperature was performed at five levels and based on the results obtained the rest of factors (sample volume and exposition time) that could potentially affect the extraction yields were optimised by a central composite design. According to the validation of the method, we propose here, to our knowledge, the first application of solid-phase microextraction for the direct analysis of chlorophenols in red wine samples.     

Determination of pyrethroid,organophosphate and organochlorine pesticides in water by headspace solid-phase microextraction

Simultaneous determination of pyrethroid, organophosphate (OP) and organochlorine (OC) pesticides in water was achieved with headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-electron-capture detection (GC-ECD). The parameters affecting HS-SPME of pesticides from water were optimized, including extraction temperature, sample and headspace volumes, and sodium chloride amounts. The effects of desorption temperature, desorption time, and position of the fibre in the GC inlet were also investigated. Extraction temperature was the most important factor affecting the recoveries of analytes, and the optimized temperature was 96°C. The addition of salt did not increase extraction efficiencies of the pesticides from the water. The optimized desorption conditions in the GC were as follows: desorption time of 10?min; desorption temperature of 260°C; and a 2?cm position of the fibre in the inlet. The method detection limits were in the low-ng/L level with a linearity range of 50–1000?ng/L for the OCs, 50–5000?ng/L for the OP, and 50–20?000?ng/L for the pyrethroids. These data demonstrated that HS-SPME is a sensitive method for the determination of pyrethroid, OC, and OP pesticides in water.     

Solid-phase micro-extraction procedure for the determination of 1,3-dichloro-2-propanol in water by on-fibre derivatisation with bis(trimethylsilyl)trifluoroacetamide

The headspace solid-phase micro-extraction technique with on-fibre derivatisation followed by gas chromatography-tandem mass spectrometry has been evaluated for the analysis of 1,3-dichloro-2-propanol in water. An asymmetric factorial design has been performed to study the influence of five experimental factors: extraction time and temperature, derivatisation time and temperature and pH. The best extraction performance is achieved in the headspace mode, with 5 mL stirred water samples (pH 4) containing 1.3 g of NaCl, equilibrated for 30 min at 25 °C, using divinylbenzene-carboxen-polydimethylsiloxane as the fibre coating. On-fibre derivatisation has been used for the first time with 50 μL of bis(trimethylsilyl)trifluoroacetamide at 25 °C during 15 min, leading to effective yields. The proposed method provides high sensitivity, good linearity and repeatability (relative standard deviation of 5.1% for 10 ng mL⁻¹ and n = 5). The limits of detection and quantification were 0.4 and 1.4 ng mL⁻¹, respectively. Analytical recoveries obtained for different water samples were approx. 100%.     

Comparative chemical composition and variability of biological activity of methanolic extracts from Hypericum perforatum L

The biovariability of Hypericum perforatum L. (St. John's Wort) grown wild in Calabria and Sardinia (Italy) was reported with the aim to characterize the species through the isolation, detection, and quantitative evaluations of chemical markers (hypericin, quercetin, rutin) by HPLC analysis. Antioxidant activity of the methanolic H. perforatum extracts showed that the Calabrian samples were more active than those from Sardinia. The antibacterial activity evidenced the best performance on the gram positive bacteria with a MIC value of 50 microg/mL. Moreover, antifungal activity of all the extracts was also tested which showed interesting results particularly on the phytopathogene fungus P. ultimum. The variability shown by the samples could be attributed to environmental factors such as chemical-physical properties, composition of the soil, geographical coordinate, altitude, and solar exposure. The phytochemical analysis and the biological activity data suggested a possible use of H. perforatum extracts in the alimentary, cosmetic, and pharmaceutical fields.     

Comparison of the endemic Azorean Hypericum foliosum with other Hypericum species: antioxidant activity and phenolic profile

Water extracts of Hypericum foliosum (HF) from five Azorean Islands were analysed for their antioxidant activity and total phenolic contents. The results were compared with those from medicinal Hypericum species (H. perforatum, H. androsaemum and H. undulatum) and also with Azorean green tea. HF exhibited strong scavenging activity (87-91%) and moderate inhibition of linoleic acid oxidation (56-72%), and presented no significant difference to the other studied plants; in contrast, the synthetic antioxidant butylated hydroxyltoluene showed antioxidant activity values of 22% and 88%, respectively. The average value of phenolics in HF was higher than that in the other Hypericum species and lower than that in tea. Additionally, the phenolic profiles of the Hypericum species were compared by reverse phase-high performance liquid chromatography/ultraviolet (RP-HPLC/UV). The method presented permits the simultaneous determination of phenolic acids, flavonoids, hypericin and hyperforin within 55 min. The most similar profile was observed between HF and H. androsaemum. This study indicates that HF is a source of bioactive compounds with potential health benefits.     

Microencapsulated and Lyophilized Propolis Co-Product Extract as Antioxidant Synthetic Replacer on Traditional Brazilian Starch Biscuit

The residue from commercial propolis extraction may have significant antioxidant power in food technology. However, among the challenges for using the propolis co-product as an inhibitor of lipid oxidation (LO) in baked goods is maintaining its bioactive compounds. Therefore, this study aimed to determine the propolis co-product extracts’ capability to reduce LO in starch biscuit formulated with canola oil and stored for 45 days at 25 °C. Two co-product extracts were prepared: microencapsulated propolis co-product (MECP) (with maltodextrin) and lyophilized propolis co-product (LFCP), which were subjected to analysis of their total phenolic content and antioxidant activity (AA). Relevant antioxidant activity was observed using the methods of analysis employed. The spray-drying microencapsulation process showed an efficiency of 63%. The LO in the biscuits was determined by the thiobarbituric acid reactive substances (TBARS) test and fatty acid composition by gas chromatography analysis. Palmitic, stearic, oleic, linoelaidic, linoleic, and α-linolenic acids were found in biscuits at constant concentrations throughout the storage period. In addition, there was a reduction in malondialdehyde values with the addition of both propolis co-product extracts. Therefore, the propolis co-product extracts could be utilized as a natural antioxidant to reduce lipid oxidation in fatty starch biscuit.     

Derivatisation for the characterisation of neutral oxosteroids by electrospray and matrix-assisted laser desorption/ionisation tandem mass spectrometry: the Girard P derivative

The identification, quantification and localisation of steroids in biological fluids and tissues are subjects of considerable importance. Not only do steroids have classical hormonal properties via binding to nuclear receptors, they can also elicit cellular responses via interactions with other proteins. For mass spectrometric analysis, neutral steroids are not readily ionised by either electrospray (ES) or matrix-assisted laser desorption/ionisation (MALDI). In this communication a derivatisation protocol is presented which allows for the rapid analysis of neutral oxosteroids by both ES and MALDI mass spectrometry. Neutral oxosteroids are derivatised to Girard P hydrazones. When analysed by tandem mass spectrometry the derivatised steroids fragment to give structurally informative spectra allowing subsequent steroid identification. The derivatisation method is simple, the reagents are commercially available, and reaction products are easily isolated from the reaction mixture. Analyte identification can be performed at the sub-pg level.     

自制离子液体固相微萃取涂层分析人体尿液中的五氯酚

建立了顶空固相微萃取与气相色谱法（HS-SPME-GC）测定人体尿液中五氯酚（PCP）的新方法。 采用溶胶-凝胶法,加入自制的离子液体键合固相微萃取涂层,优化了萃取温度、萃取时间、pH值、离子强度及解吸时间。 结果表明,样品中加入3 g NaCl,溶液的pH值为2,并以一定速度搅拌的条件下,在80 ℃顶空萃取50 min,300 ℃下解吸5 min,方法的检测限为5.0 ng/L,线性范围为0.05～100 μg/L,相对标准偏差(RSD)为5.9%,加标回收率为106.6%。     

Evaluation of the antimicrobial and antioxidant activities of Origanum dictamnus extracts before and after encapsulation in liposomes

The antioxidant and antimicrobial activity of methanol or dichloromethane extracts of O. dictamnus, produced from wild and organic cultivated specimens, were determined. The Rancimat and malondialdehyde (MDA) by HPLC methods were used to measure the antioxidant action, in comparison with that of the common commercial antioxidants butylated hydroxytoluene (BHT) and alpha-tocopherol. The extracts that presented high antioxidant activity were encapsulated in liposomes and their antioxidant action was again estimated using differential scanning calorimetry (DSC). Thermaloxidative decomposition of the samples (pure liposomes and encapsulated extracts) and the modification of the main transition temperature for the lipid mixture and the splitting of the calorimetric peak in the presence of the antioxidants were also studied by the DSC method. All extracts showed antioxidant and antimicrobial activities. Their action proved superior to alpha-tocopherol. The methanol extract of organic cultivated O. dictamnus (240 ppm) showed higher activity than butylated hydroxytoluene. After encapsulation in liposomes the antioxidant as well as antimicrobial activities proved to be higher than those of the same extracts in pure form.     

SPME determination of volatile aldehydes for evaluation of in-vitro antioxidant activity

The in-vitro antioxidant activity of natural (essential oils, vitamin E) or synthetic substances ( tert-butyl hydroxy anisole (BHA), Trolox) has been evaluated by monitoring volatile carbonyl compounds released in model lipid systems subjected to peroxidation. The procedure employed methodology previously developed for the determination of carbonyl compounds as their pentafluorophenylhydrazine derivatives which were quantified, with high sensitivity, by means of capillary gas chromatography with electron-capture detection. Linoleic acid and sunflower oil were used as model lipid systems. Lipid peroxidation was induced in linoleic acid by the Fe2+ ion (1 mmol L-1, 37 degrees C, 12 h) and in sunflower oil by heating in the presence of O2 (220 degrees C, 2 h). The change in hexanal (the main lipoxidation product) concentration found in the lipid matrix subjected to oxidation with and without the substance being tested was used to calculate the antioxidant protection effect. These procedures were employed to evaluate the antioxidant activity of the essential oils of cilantro ( Coriander sativum L.), fennel ( Foeniculum vulgare Mill.), rosemary ( Rosmarinus officinalis L.), "salvia negra" ( Lepechinia schiedeana), and oregano ( Origanum vulgare L.), and the well-known antioxidants BHA, vitamin E, and Trolox, its water-soluble analog. In the sunflower oil system, the essential oils had a stronger protective effect against lipid peroxidation than BHA, vitamin E, and Trolox within the range of concentrations examined (1-20 g L-1). The highest protecting effect, corresponding to a 90% drop in hexanal release, was observed for cilantro oil at 10 g L-1.     

Effects of St John's wort (Hypericum perforatum L.) extracts on epileptogenesis

The purpose of this study was to investigate the effects of treatment with water, n-butanol and ether extracts of Hypercom perforatum L. on epileptogenesis in rabbits. Animals from the control group received solvent-ethanol, and the kindling model of epilepsy was used. Epileptic focus was induced in Chinchilla rabbits by stimulation of the hippocampus. The following parameters were determined: the minimum current strength necessary to induce after-discharge (AD) - discharges appearing after cessation of stimulation; AD duration; the number of stimulations necessary to induce spontaneous kindling; and the latency time for the development of full kindling. The results obtained indicate that epileptogenesis is influenced by Hypericum perforatum L. extract treatment. Animals treated with an ether extract of Hypericum perforatum L. required significantly weaker minimum current strengths for the development of epileptogenic focus, and displayed longer AD times, while the number of electro-stimulations necessary for full kindling was less. In contrast, animals treated with water and n-butanol extracts required increased electro-stimulations for the development of epileptic discharge, and displayed shortened AD durations versus controls.     

High performance liquid chromatography/electrospray mass spectrometry of Hypericum perforatum extracts

Hypericum perforatum L. (St. John's Wort) is a widely distributed herbaceous perennial plant which has been well known as a medicinal plant since antiquity. In recent years, H. perforatum has received increasing attention for the treatment of depression and other neuralgic disorders. The main constituents of H. perforatum extract include flavonoids, naphthodianthrones, phloroglucinols, essential oils and xanthones. The present work reports the analysis of naphthodianthrones and phloroglucinols in H. perforatum extracts by means of high performance liquid chromatography (HPLC) coupled simultaneously to a diode array detector (DAD) and electrospray mass spectrometry (ESI-MS). Hypericin, pseudohypericin, hyperforin and adhyperforin were separated and identified on the base of their on-line UV and mass spectra. Quantitative analysis of hypericin derivatives in different extracts of H. perforatum using DAD and MS detectors was performed. In addition, direct infusion ESI-MS of H. perforatum extracts was applied to obtain rapid mass fingerprints of constituents present in the sample.     

正交试验优化-顶空固相微萃取-气相色谱-串联质谱法测定水中戊二醛

建立了顶空固相微萃取-气相色谱-串联质谱测定水中戊二醛的方法。设计5因素4水平完整的正交试验,通过极差分析获得顶空固相微萃取优化条件。10 mL,pH 1的水样加入6 g NaCl,经非极性PDM S,100μm纤维头于75℃萃取25 min,210℃解析进样0.2 min。采用VF-5(60 m×0.25 mm×0.25μm)色谱柱程序升温分离,选择多反应监测(M RM)模式采集质谱信息。以m/z 82/54为定量离子,以m/z 82/39为定性离子,外标法定量。结果表明,戊二醛质量浓度在0.02~0.6 mg/L范围内线性良好,相关系数(r)>0.9996,方法检出限7μg/L,定量限20μg/L。低(0.04 mg/L)、中(0.1 mg/L)、高(0.4 mg/L)3个水平加标回收率为87.4%~103.7%,相对标准偏差(RSD)<6%。方法适用于测定水中的戊二醛。     

In-tube extraction for enrichment of volatile organic hydrocarbons from aqueous samples

In-tube extraction (ITEX) is a novel solventless extraction technique in which a headspace syringe with a needle body filled with a sorbent (here: Tenax TA) is used. The analytes are extracted from sample headspace by dynamic extraction. The needle body is surrounded by a separate heater, which is used for thermal desorption of analytes into the injection port of a GC system. We report here for the first time the optimization and evaluation of a fully automated analytical method based on ITEX. As target analytes, 19 common groundwater contaminants such as halogenated volatiles and monoaromatic compounds have been chosen. Method related parameters such as extraction temperature, number of extraction cycles, extraction and desorption volume as well as extraction and desorption flow rates were investigated in detail. The linear dynamic range of the ITEX method ranged over six orders of magnitude between 0.028 microg/L and 1218 microg/L with linear correlation coefficients between 0.990 and 0.998 for the investigated compounds. Method detection limits for monoaromatic compounds were between 28 ng/L (ethylbenzene) and 68 ng/L (1,2,4-trimethylbenzene). For halogenated volatile organic compounds, method detection limits between 48 ng/L (chloroform) and 799 ng/L (dichloromethane) were obtained. The precision of the method with external calibration was between 3.1% (chloroform ethylbenzene) and 7.4% (1,2,3-trimethylbenzene).     

Low‐temperature headspace‐trap gas chromatography with mass spectrometry for the determination of trace volatile compounds from the fruit of Lycium barbarum L.

The total saccharides content of Lycium barbarum L. is very high, and a high temperature would result in saccharide decomposition and the emergence of a large amount of water. Moreover, the volatile compounds from the fruit of L. barbarum L. are rather low in concentration. Hence, it is difficult for a conventional headspace method to study the volatile compounds from the fruit of L. barbarum L. Since headspace‐trap gas chromatography with mass spectrometry is an excellent method for trace analysis, a headspace‐trap gas chromatography with mass spectrometry method based on low‐temperature (30°C) enrichment and multiple headspace extraction was developed to explore the volatile compounds from the fruit of L. barbarum L. The headspace of the sample was extracted in 17 cycles at 30°C. Each time, the compounds extracted were concentrated in the trap (Tenax TA and Tenax GR, 1:1). Finally, all the volatile compounds were delivered into the gas chromatograph after thermal desorption. With the method described above, a total of 57 compounds were identified. The identification was completed by mass spectral search, retention index, and accurate mass measurement.     

Relationship of electrochemical oxidation of catechins on their antioxidant activity in microsomal lipid peroxidation.

The oxidation potentials of catechins were measured by employing flow-through column electrolysis. The oxidation potentials of catechins were shown to depend on their structures. At the same time, the antioxidant activity of catechins on NADPH-dependent lipid peroxidation in rat liver microsomes was evaluated. Catechins showed a 50% inhibition of lipid peroxidation in the concentration range of 10-51 microM. Among those studied, galloylated catechins exhibited stronger antioxidant activities than those of nongalloylated catechins. A quantitative relationship has been obtained to describe the antioxidant activity of catechins: log IC50 (microM)= 1.56+2.49E1/2 (V)-0.29 logP (r=0.907), where IC50 represents the concentration for 50% inhibition of lipid peroxidation, E1/2 represents the half-wave potential of the first oxidation wave, and P represents the octanol/water partition coefficient. This relationship suggested two important characteristics determining catechin antioxidant activity, namely the ease of oxidation and the lipophilicity.