Analysis of the stable free radical scavenging capability of artificial polyphenol mixtures and plant extracts by capillary electrophoresis and liquid chromatography–diode array detection–tandem mass spectrometry

The oxidation process of phenolic compounds of an artificial mixture consisting of six polyphenols and the extract of eggplant (Solanum melongena) skin was monitored by using capillary zone electrophoresis and liquid chromatography–diode array detection–tandem mass spectrometry. The methods developed enabled simultaneous evaluation of the antioxidative capability of each compound. The above oxidation process was carried out using two radicals, viz. the 2,2-diphenyl-1-picrylhydrazyl and hydroxyl radicals generated via the Fenton reaction. The radical scavenging effects of artificial and natural polyphenol mixtures were compared.     

Electrophoretic identification and quantitation of compounds in the polyphenolic fraction of extra-virgin olive oil

A capillary zone electrophoresis method has been carried out to determine and quantitate some compounds of the polyphenolic fraction of virgin olive oil which have never previously been determined before using capillary electrophoresis, such as elenolic acid, ligstroside aglycon, oleuropein aglycon, and (+)-pinoresinol. The compounds were identified using standards obtained by semipreparative high-performance liquid chromatography (HPLC). A detailed method optimization was performed to separate the phenolic compounds present in olive oil using a methanol-water extract of Picual extra-virgin olive oil, and different extraction systems were compared (C18-solid phase extraction (SPE), Diol-SPE, Sax-SPE and liquid-liquid extraction). The optimized parameters were 30 mM sodium tetraborate buffer (pH 9.3) at 25 kV with 8 s hydrodynamic injection, and the quantitation was carried out by the use of two reference compounds at two different wavelengths.     

Capillary electrophoresis,high‐performance liquid chromatography,and thin‐layer chromatography analyses of phenolic compounds from rapeseed plants and evaluation of their antioxidant activity

Rapeseed plants, known for oil production, are also known to contain phenolic compounds such as phenolic acids and flavonoids, with potential antioxidant and anticancer activities. The separation and identification of 11 phenolic acids in rapeseed extracts (including leaves, flowers, Chinese seeds, Belgian seeds, and cake) by capillary electrophoresis were investigated. The results were compared with those obtained with high‐performance liquid chromatography and thin‐layer chromatography and showed that the capillary electrophoresis technique offers several advantages for the identification of phenolic compounds in various rapeseed extracts. The antioxidant activity of rapeseed extracts and reference compounds was evaluated using four different approaches, namely, 2,2′‐azinobis‐ (3‐ethylbenzohiazoline‐6‐sulfonic acid assay, free radical 2,2‐diphenyl‐1‐picrylhydrazyl assay, electron paramagnetic resonance spectroscopy and the measurement of the total polyphenol content. The contents of total polyphenols in the tested extracts were ranging between 5.4 and 21.1% m/m and ranked as follows: Chinese seeds ? Belgian seeds ? Flowers ? Cake ? Leaves.     

Identification of phenolic compounds from pollen extracts using capillary electrophoresis–electrospray time-of-flight mass spectrometry

In this work, a new, easy and rapid method of analyzing phenolic compounds in pollen extract, based on capillary electrophoresis coupled with electrospray ionization time-of-flight-mass spectrometry (CE–ESI–TOF–MS), has been developed. A systematic investigation of separation parameters has been performed with respect to resolution, sensitivity, analysis time and peak shape. The electrophoretic parameters and electrospray conditions must be optimized to obtain reproducible analyses. Using this method, several important phenolic compounds such as acetin-glucoside, 7-O-methylherbacetin-3-sophoroside, galloyl-glucose, quercetin-3-sophoroside, apigenin-6,8-di-C-glycoside, quercetin-3-rutinoside, genistein-7-O-β-D-glucoside, luteolin-7-O-glucoside, apigenin-7-O-glucoside and 2′,4′,6′-trihydroxy-3′-formyldihydrochalcone have been determined directly from pollen extract. The efficiency, the rapidity, the small amounts of sample required, and the high resolution of CE coupled with the sensitivity, the selectivity, the accurate masses and the true isotopic patterns obtained using TOF-MS point to the potential of this approach for identifying the phenolic compounds present in pollen.     

Chemical composition and antioxidant activity of Borago officinalis L. leaf extract growing in Algeria

The aqueous and hydroalcoholic extracts of borage (Borago officinalis) leaves from Annaba region (Algeria) were preliminary analyzed for their phenolic profile (total phenolics, total flavonoids, total flavonols, total tannins and total anthocyanins). These extracts were evaluated for their antioxidant properties by different methods such as DPPH radical scavenging, test NBT and total antioxidant activity. The two extracts have exhibited a high antiradical capacity. Indeed, the ethanolic extract showed the lower IC50 values and the highest amount of phenolics (94.09 ± 1.72 mg gallic acid/g dry extract). Using LC-MS/MS analysis, it was possible to identify phenolic acids, flavonoids, sterol and for the first time oleuropein was identified in the aqueous extract of the plant. The obtained results have demonstrated that phenolic compounds are the major contributor to the antioxidant activity of plants.     

HPLC-ESI-MS/MS analysis of phenolics and in vitro antioxidant activity of Epilobium angustifolium L.

The aerial parts of Epilobium plants are widely used as folk medicine and food around the world. The present study was aimed to investigate the antioxidant activities and active chemical constituents from Epilobium angustifolium L. The results revealed that the EtOAc extract, rich in phenolic compounds and flavonoids (16.81 ± 0.67 g GAE/100 g extract and 4.95 ± 0.21 g QE/100 g extract, respectively), possessed significantly antioxidant activities in reducing power, DPPH radical scavenging activity, ABTS radical scavenging activity and highly in inhibiting lipid peroxidation activity. Simultaneously, active fractions F to H from EtOAc extracts showing potent in vitro antioxidant activities also contained high content of total phenolic and flavonoid. Twenty-eight compounds were identified as phenolic compounds and flavonoids by LC-MS/MS. The results illustrate that the E. angustifolium L., which is rich in phenolics, could be used as a natural resource of antioxidant ingredient.     

Determination of phenolic compounds,in vitro antioxidant activity and characterization of secondary metabolites in different parts of Passiflora cincinnata by HPLC-DAD-MS/MS analysis

Abstract

Ethanol extracts of different parts of Passiflora cincinnata were obtained by maceration. The total phenolic and flavonoid contents were evaluated. The antioxidant activities were determined by β-carotene-linoleic acid bleaching test, 2,2-diphenyl-1-picrylhydrazil (DPPH), and 2,2’-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging. The crude ethanol stem extract showed the highest amount of total polyphenols (45.53?mg gallic acid equivalent/g) while the highest total flavonoid contents (1.42?mg of quercetin equivalent/g) were observed in the leaf extract. The lowest IC₅₀ (25.65?μg/ml) by the DPPH method was observed for the stem extract. The ABTS method showed a significant antioxidant activity for all investigated extracts. The secondary metabolite composition of ethanol extracts was assessed by HPLC-DAD-MS/MS analysis, leading to the identification of fourteen secondary metabolites in P. cincinnata extracts. These results showed the potentiality of this species as a source of phenolic compounds and antioxidants.     

Phytochemical composition,in vitro antioxidant activity and antibacterial mechanisms of Neolamarckia cadamba fruits extracts

Aqueous extracts of Neolamarckia cadamba fruits prepared at different maturity stages were used for the analysis of various phytochemicals, and their antioxidant and antibacterial activities were determined. Ripe fruit extract had highest phenolics (3.14 mM GAE/ g fruit extract) with caffeic acid, tannic acid, syringic acid and quercetin as major phenolic compounds. The ripe fruit extract showed lowest IC₅₀ values in DPPH radical scavenging assay (231.33 μg fruit extract/ mL), and highest ABTS radical scavenging activity (111.18 μM TEAC/g). Immature fruit extract showed lowest minimum inhibitory concentration against tested bacteria, and the antibacterial activity was probably due to membrane permeation, as was evident by leakage of genetic material and reduction in propidium iodide uptake by bacterium; and by inhibition of sugar and amino acid uptake. The appreciable amount of phenolic compounds and biological activities in the aqueous extracts of N. cadamba fruits suggests it's potential application as natural preservative.     

Fast separation and determination of carnosic acid and rosmarinic acid in different rosemary (Rosmarinus officinalis) extracts by capillary zone electrophoresis with ultra violet-diode array detection

Summary Carnosol, carnosic acid, rosmarinic acid and other not identified phenolic compounds were separated by capillary zone electrophoresis (CZE) using a 40-cm long capillary and a 20 mM tetraborate buffer (pH 9.0), within 3 min. A UV-diode array detector was employed to collect spectra of phenolic compounds. The effect of some separation parameters on peak resolution and migration time of phenolic species present in a refined rosemary extract was studied. The repeatability of the method was also investigated: the intraday relative standard deviation on total peak area was less than 4%, while the intraday relative standard deviation on migration time was less than 0.6%. Moreover the CZE method showed good sensitivity (0.0007 μg mL¹ for carnosic acid and rosmarinic acid). Carnosic acid and rosmarinic acid have been quantified in different commercial extracts of rosemary. Finally, the optimized method was also applied to evaluate the recovery of these two compounds when different organic solvents were employed during the extraction procedure.     

Analysis of drugs, natural and bioactive compounds containing phenolic groups by capillary electrophoresis coupled to mass spectrometry

This review summarizes the use of capillary electrophoresis (CE) coupled to mass spectrometry (MS) for the analysis of phenolic compounds and its latest developments. Special attention is paid to the different interfaces. The instrumental setups are discussed and demonstrated in a high number of real applications.     

Analysis of synthetic chemical drugs in adulterated Chinese medicines by capillary electrophoresis/electrospray ionization mass spectrometry

Sixteen synthetic chemical drugs, often found in adulterated Chinese medicines, were studied by capillary electrophoresis/UV absorbance (CE/UV) and capillary electrophoresis/electrospray ionization mass spectrometry (CE/ESI-MS). Only nine peaks were detected with CZE/UV, but on-line CZE/MS provided clear identification for most compounds. For a real sample of a Chinese medicinal preparation, a few adulterants were identified by their migration times and protonated molecular ions. For coeluting compounds, more reliable identification was achieved by MS/MS in selected reaction monitoring mode. Micellar electrokinetic chromatography (MEKC) using sodium dodecyl sulfate (SDS) provided better separation than capillary zone electrophoresis (CZE), and, under optimal conditions, fourteen peaks were detected using UV detection. In ESI, the interference of SDS was less severe in positive ion mode than in negative ion mode. Up to 20 mM SDS could be used in direct coupling of MEKC with ESI-MS if the mass spectrometer was operated in positive ion mode. Because of better resolution in MEKC, adulterants can be identified without the use of MS/MS.     

Comparative study of aqueous and non-aqueous capillary electrophoresis in the separation of halogenated phenolic and bisphenolic compounds in water samples

Capillary zone electrophoresis methods, based on either aqueous and non-aqueous solutions as running buffers and UV spectrophotometric detection, have been developed and optimized for the separation of several halogenated phenolic and bisphenolic compounds, suspected or proved to exhibit hormonal disrupting effects. Both aqueous capillary electrophoresis (CE) and non-aqueous capillary electrophoresis (NACE) methods were suitable for the analysis of compounds under study. The separation of the analytes from other 25 potentially interfering phenolic derivatives was achieved with NACE method. Large-volume sample stacking using the electroosmotic flow pump (LVSEP) was assayed as on-column preconcentration technique for sensitivity enhancement. LVSEP-CE and LVSEP-NACE improved peak heights by 5-26 and 16-330 folds, respectively. To evaluate their applicability, the capillary electrophoresis methods developed were applied to the analysis of water samples, using solid-phase extraction as sample pre-treatment process.     

Unique phenolic constituent in Cimicifuga dahurica (Turcz.) Maxim. through Box–Behnken design and response surface methodology

Cimicifuga dahurica (Turcz.) Maxim. exerts significant antioxidative due to its high phenolic constituent content. In this study, the extraction condition of the phenolic constituents and antioxidant effect was optimized by the Box‐Behnken design and response surface methodology. Eleven main bioactive analytes of Cimicifuga dahurica (Turcz.) Maxim. were simultaneously quantified by high‐performance capillary electrophoresis with diode‐array detector to assess the effect of extraction technology. The optimal extraction parameters were determined as: the concentration of ethanol 56.21%, liquid/solid ratio 14.65:1, and extraction time 1.64 h for 2.67 times. According to the results, a maximal value of total phenolic acids (3.67 mg/g) was obtained. Meanwhile, the influence of different extraction technology on antioxidant activities were evaluated by 1,1‐diphenyl‐2‐picrylhydrazyl, 2,2′‐azino‐bis‐(3‐ethylbenzthiazoline‐6‐sulfonate), ferric reducing antioxidant power and hydroxyl radical scavenging method. The results presented here showed that the content of phenolic acid and antioxidant effect was much higher than the European Pharmacopoeia. Altogether, this method successfully applied response surface methodology to optimize the Cimicifuga dahurica (Turcz.) Maxim. extract with high antioxidant activities.     

Phenolic Compound Profile by UPLC-MS/MS and Encapsulation with Chitosan of Spondias mombin L. Fruit Peel Extract from Cerrado Hotspot—Brazil

Taperebá (Spondias mombin L.) is a native species of the Brazilian Cerrado that has shown important characteristics such as a significant phenolic compound content and biological activities. The present study aimed to characterize the phenolic compound profile and antioxidant activity in taperebá peel extract, as well as microencapsulating the extract with chitosan and evaluating the stability of the microparticles. The evaluation of the profile of phenolic compounds was carried out by UPLC-MS/MS. The in vitro antioxidant activity was evaluated by DPPH and ABTS methods. The microparticles were obtained by spray drying and were submitted to a stability study under different temperatures. In general, the results showed a significant content of polyphenols and antioxidant activity. The results of UPLC-MS/MS demonstrated a significant content of polyphenols in taperebá peel, highlighting the high content of ellagic acid and quercetin compounds. There was significant retention of phenolic compounds when microencapsulated, demonstrating high retention at all evaluated temperatures. This study is the first to microencapsulate the extract of taperebá peel, in addition to identifying and quantifying some compounds in this fruit.     

超高效液相色谱-四极杆-飞行时间质谱定性研究茶叶籽中的酚类化合物

采用超高效液相色谱(UHPLC)-四极杆-飞行时间质谱(Q-TOF/MS)技术定性分析茶叶籽中的酚类化合物。茶叶籽样品经乙醇水溶液提取后经反相色谱分离,通过Q-TOF/MS进行化合物的鉴定。基于山茶属及相关植物化学组成的文献,建立了一个含有106种酚类化合物的数据库。对UHPLC-Q-TOF/MS采集得到的一级质谱数据进行数据库检索,然后对检索到的化合物色谱峰进行二级质谱扫描,根据得到的碎片离子推断化合物的结构。初步推断出茶叶籽提取物中的24种酚类化合物,包括13种酚酸类、4种儿茶素类和7种黄酮类化合物,并通过与标准品比对,进一步确证了这些化合物。结果表明UHPLC-Q-TOF/MS技术可以用于对茶叶籽中酚类化合物进行快速、准确、可靠的定性分析,促进新化合物的发现与鉴别。     

Capillary electrophoretic separation of phenolic diterpenes from rosemary

The major phenolic diterpenes responsible for the antioxidant properties of rosemary extracts, namely carnosol and carnosic acid, were separated by capillary zone electrophoresis (CZE) using a 56 cm long uncoated fused-silica capillary and a 50 mM disodium tetraborate buffer of pH 10.1. The effect of the buffer type, pH and concentration, and the capillary length on the separation, was studied. Carnosol and carnosic acid were identified in the electrophoregrams of rosemary extracts through their migration times and UV spectra obtained by CZE analysis of pure compounds isolated from a rosemary extract by HPLC fractionation. The CZE method had good reproducibility (relative standard deviation less than 5%) and was applied to compare the contents of carnosol and carnosic acid in solid and oil-dispersed commercial extracts of rosemary and in rosemary leaves. The separation of carnosol and carnosic acid was accomplished in less than 11 min.     

Bioactive components of the hop strobilus: comparison of different extraction methods by capillary electrophoretic and chromatographic methods

In the present study, the composition of the hop strobilus extract by using different extraction methods under different solvent conditions was analysed and compared. Several separation methods were applied to obtaining detailed information about the hop extract: capillary zone electrophoresis (CZE), high-performance liquid chromatography-mass-spectrometry (HPLC-MS/MS) and gas chromatography-mass-spectrometry (GC-MS). The electropherograms of different extracts varied dramatically. The oxidation reaction of the hop strobilus extract was examined.     

Complete assignment of bilberry (Vaccinium myrtillus L.) anthocyanins separated by capillary zone electrophoresis

Capillary zone electrophoresis (CZE) mobilities of fifteen anthocyanins in bilberry extract were completely characterized. Four minor anthocyanins in bilberry extract (malvidin 3-O-alpha-L-arabinopyranoside (Mv 3-ara), peonidin 3-O-beta-D-galactopyranoside (Pn 3-gal), peonidin 3-O-alpha-L-arabinopyranoside (Pn 3-ara), and petunidin 3-O-alpha-L-arabinopyranoside (Pt 3-ara)) that remained unidentified in our previous CZE study were isolated from the bilberry extract, and the chemical structures were assigned by NMR and MS. Their CZE mobilities were then precisely examined together with those of other major anthocyanins in the extract. When the CZE mobilities of the fifteen anthocyanins assigned here were plotted against their molecular weight/numbers of free phenolic group, it was found that separation of anthocyanins by CZE is primarily determined by the type of conjugated sugar present, and secondly by the aglycon structure.     

Screening of antioxidant phenolic compounds in Chinese Rhubarb combining fast counter‐current chromatography fractionation and liquid chromatography/mass spectrometry analysis

In this paper, an effective method combing fast elution‐extrusion counter‐current chromatography (CCC) and LC/MS for rapid screening of antioxidative phenolic compounds in Chinese Rhubarb is presented. An integrated three‐coil CCC column (40 mL each coil) was used to accomplish the optimization of biphasic liquid system. In a single run (approximately 40 min), the solvent system composed of n‐hexane/ethyl acetate/methanol/water (1:1:1:1, v/v) was selected as optimum CCC liquid system for fast fractionation of the crude ethanol extract. With a 140 mL‐capacity CCC instrument, 100 mg Chinese Rhubarb extract was separated under the optimized conditions, producing six fractions in only 100 min. The quantities of each fraction were ～15 mg. In addition, each fraction was subjected to antioxidant activity assay and characterized by LC/MS analysis. Fifty compounds, including phenolic acids, phenolic glucosides and hydroxyanthraquinones, were detected by LC/MS/MS analysis. As a result, gallic acid together with Fr I showed excellent antioxidant activity, which was well consistent with previous studies and exhibited great potential for natural drug discovery program of the present method.