Binding study of Flos Lonicerae Japonicae with bovine serum albumin using centrifugal ultrafiltration and liquid chromatography

The screening and analysis of bioactive components in traditional Chinese medicines (TCMs) is very important not only for the quality control of Chinese herbs but also for elucidating the therapeutic principles. This study developed a new method for screening and analyzing bioactive compounds from TCMs using centrifugal ultrafiltration coupled with high-performance liquid chromatography. The method was successfully applied in the binding study of Flos Lonicerae Japonicae with bovine serum albumin (BSA), and 11 compounds were found to be bound with the BSA. Eight of them were positively identified as chlorogenic acid, caffeic acid, rutin, quercetin-3-O-glucoside, luteolin-7-O-glucoside, lonicerin, 3, 5-di-O-caffeoyl quinic acid and 3,4-di-O-caffeoyl quinic acid. Another three compounds were tentatively identified as two isomers of chlorogenic acid and one isomer of di-O-caffeoyl quinic acid by comparing the UV data and MS data with the previous reports. Based on modern pharmacological study, these compounds are the major bioactive components in Lonicera japonica. Therefore, the proposed method could be a good approach to predicting the potential bioactivities of multiple compounds in TCMs simultaneously.     

Simultaneous qualitation and quantification of thirteen bioactive compounds in Flos lonicerae by high-performance liquid chromatography with diode array detector and mass spectrometry

A high-performance liquid chromatography (HPLC) with diode array detector (DAD) and electrospray ionization mass spectrometry (ESI-MS) was established for the simultaneous determination of thirteen bioactive compounds in Flos Lonicerae. The optimal chromatographic conditions were obtained on a C(18) column (250x4.6 mm, 5.0 microm) with the column temperature at 30 degrees C. The mobile phase was composed of (A) acetic acid aqueous (0.4%, v/v) and (B) acetonitrile using a gradient elution, the flow rate was 1 ml/min. Detection wavelengths were set at 240 nm for iridoids (loganin, sweroside, secoxyloganin and centauroside), 330 nm for phenolic acids (chlorogenic acid, caffeic acid, 4,5-di-O-caffeoyl quinic acid and 3,4-di-O-caffeoyl quinic acid) and 360 nm for flavonoids (rutin, hyperoside, quercetin-3-O-glucoside, luteolin-7-O-glucoside and lonicerin). The identities of the peaks were accomplished by comparing retention times, UV and mass data with reference compounds under the same conditions. All calibration curves showed good linear regression (r(2)>0.9983) within test ranges. The developed method provided satisfactory precision and accuracy with overall intra-day and inter-day variations of 0.78--1.85% and 1.13--2.36%, respectively, and the overall recoveries of 91.3--104.2% for the thirteen compounds analyzed. The verified method was successfully applied to quantitative determination of the three types of bioactive compounds in ten commercial Flos Lonicerae samples from different markets in China. The analytical results demonstrated that the contents of the thirteen analytes were relatively variant.     

Liquid chromatography-diode array detection-electrospray ionisation mass spectrometry/nuclear magnetic resonance analyses of the anti-hyperglycemic flavonoid extract of Genista tenera. Structure elucidation of a flavonoid-C-glycoside

The anti-hyperglycemic flavonoid extract obtained from Genista tenera was first studied by liquid chromatography (LC)-diode array detection (DAD) which showed the presence of two major compounds. One of them was identified as genistein-7-O-glucoside. Luteolin-7-O-glucoside was detected as a minor constituent, while luteolin-7,3'-di-O-glucoside and rutin were found in trace amounts. LC-DAD-ESI-MS and NMR were used to confirm the structure of these compounds and allowed the elucidation of the structure of the unknown major compound, which is the flavonoid 5,7,4'-trihydroxyisoflavone-8-C-glucoside.     

Hydrolysis of flavonoid glycosides by propolis β-glycosidase

Flavonoids generally occur as O-glycosides with sugars bound in nature, while aglycones and their derivatives are the main flavonoids in propolis. The objective of this work was to study the propolis β-glycosidase activities toward flavonoid β-glycosides and their conjugated forms. β-Glycosidase was extracted from propolis, incubated with ?avonoid glycosides, and analysed for aglycone formation by HPLC. The results demonstrated that glucose conjugates were rapidly hydrolysed, but not conjugates with other sugars, i.e. rutin and naringin. The rate and extent of deglycosylation depends on the structure of the ?avonoid and the position of the sugar substituitions. Quercetin 3-O-glucoside had the highest percent of hydrolysis, while quercetin 7-O-glucoside was the least hydrolysed. The K(m) values for hydrolysis of apigenin 7-glucoside and luteolin-7-O-glucoside were 13 μM and 20 μM, respectively.     

DNA binding studies of a solvatochromic fluorescence probe 3-methoxybenzanthrone

A fluorescence probe of 3-methoxybenzanthrone (MBA) exhibits significant solvatochromic characteristics correlated with the polarity of solvents. The interaction of the solvatochromic fluorescence probe with calf thymus DNA (ct-DNA) has been investigated. In the presence of ct-DNA the fluorescence of MBA is strongly quenched with a blue-shift of emission peak and a hypochromism in absorption spectra. The absorption spectra, fluorescence quenching and fluorescence polarization experiments show that the MBA molecule as an intercalator is inserted into the base-stacking domain of the ct-DNA double helix, and the interaction of the nucleobases with the MBA molecule causes quenching of fluorescence and hypochromism in the absorption spectra. The intrinsic binding constant and the binding site number were determined to be 1.70 x 10(5) mol l-1 in base pairs and six, respectively. The I0/I versus [ct-DNA] plot shows linear relationship in the range covering 4.3 x 10(-7)-1.02 x 10(-4) mol l-1 in base pairs which can be used for ct-DNA determination. The limit of detection was found to be 4.3 x 10(-7) mol l-1 in base pairs (0.5 microgram ml-1).     

Isolation and purification of four flavonoid constituents from the flowers of Paeonia suffruticosa by high-speed counter-current chromatography

Four flavonoids, apigenin-7-O-neohesperidoside, luteolin-7-O-glucoside, apigenin-7-O-glucoside and kaempferol-7-O-glucoside have been isolated and purified for the first time from the flowers of Paeonia suffruticosa by high-speed counter-current chromatography with a two-phase solvent system composed of ethyl acetate-ethanol-acetic acid-water (4:1:0.25:5, v/v). Then, 5 mg apigenin-7-O-neohesperidoside, 4 mg luteolin-7-O-glucoside, 9 mg apigenin-7-O-glucoside and 2.5 mg kaempferol-7-O-glucoside could be obtained after injecting 40 mg sample and their purities were 94, 97, 97 and 96%, respectively. All these constituents were identified by mass spectrometry and nuclear magnetic resonance.     

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.     

Reactive oxygen species scavenging activity of flavone glycosides from Melilotus neapolitana

One new and six known flavone glycosides were isolated from the MeOH extract of Melilotus neapolitana Ten. The new compound, identified as 7-O-beta-D-glucopyranosyloxy-4',5-dihydroxy-3-[O-alpha-L-rhamnopyranosyl-(1-->6)-3-O-beta-D-glucopyranosyloxy]flavone (1) by 1D and 2D NMR techniques and mass spectra, was isolated along with kaempferol-3-O-rutinoside (2), kaempferol-3-O-glucoside (3), rutin (4), quercetin-3-O-glucoside (5), isorhamnetin-3-O-rutinoside (6), and isorhamnetin-3-O-glucoside (7). The antioxidant and radical scavenging activities of these compounds and the whole crude methanol extract were evaluated. The organic extract can inhibit MDA marker's synthesis by 57%. All the metabolites displayed good reducing power, with the kaempferol (2,3) and isorhamnetin derivatives (6,7) being less active than the corresponding quercetin derivatives 4,5.     

Systemic chemical characterization of Lemna minor by UHPLC-Q-Exactive Orbitrap MS coupled with parallel reaction monitoring

Lemna minor L. (LM) has been used for measles opacity, rubella itching, edema, and oliguria, and the main active ingredients were flavonoids, namely, apigenin, apigenin-7-O-glucoside, and luteolin-7-O-glucoside. However, few systematic analyses of their constituents have been performed; thus, it was necessary to establish a fast and efficient method to identify the chemical composition of LM. In this study, the UHPLC-Q-Exactive Orbitrap mass spectrometry coupled with parallel reaction monitoring was established. Finally, a total of 112 constituents, including 30 dipeptides, 28 nucleosides, 11 amino acids, 10 organic acids, 10 flavonoids, and 23 other compounds, were identified by MS, diagnostic fragment ions, and retention time. One hundred one of those chemicals were first found in LM, which was very beneficial for the further development and utilization of nutriments and the medicinal use of LM.     

刺五加叶中黄酮类化合物的结构鉴定

利用电喷雾质谱发现刺五加叶中存在4种黄酮类化合物,进一步分离得到其中的两种,经核磁质谱鉴定,一种为槲皮甙(槲皮素－3－O－α－L－鼠李糖),另一种为金丝桃甙(槲皮素－3－O－β-D－半乳糖).其余两种难以分离的黄酮甙经电喷雾多级串联质谱分析,初步推断为槲皮素和芦丁(槲皮素－3-O－芦丁糖).以上4种均为黄酮醇类化合物,除金丝桃甙外,其它3种为刺五加叶中尚未见报道的黄酮类成分.     

Inhibitory effects of flavonoids on free radical-induced hemolysis and their oxidative effects on hemoglobin

To investigate the effects of flavonoids on free radical-mediated biological membrane damage and the interaction of flavonoids with heme proteins, we studied the effects of quercetin, its glycosides (rutin and quercetin-3-O-glucoside), morin and (-)epicatechin on the hemolysis of the bovine erythrocytes induced by the hydrophilic free radical initiator, 2,2'-azobis(2-amidinopropane)dihydrochloride (AAPH), and their interaction with hemoglobin. These flavonoids retarded the onset of the hemolysis dose-dependently. The effects of quercetin and other flavonoids were much greater than those of dihydric-phenols studied previously. The inhibitory effects of quercetin and its glycosides were stronger than those of morin and (-)epicatechin. In the absence of AAPH, the relatively hydrophobic flavonoids quercetin and morin induced the oxidation of oxyhemoglobin to methemoglobin. Oxidation by quercetin was especially marked. However, this oxidation did not induce hemolysis. These findings indicate that relatively hydrophobic flavonoids penetrate the cytoplasm of erythrocytes, interact with hemoglobin, and oxidize the heme iron.     

Simultaneous determination of seven flavonoids in Potentilla multifida by HPLC

A reversed-phase high-performance liquid chromatographic method is described for the simultaneous determination of seven flavonoids in Potentilla multifida: hyperin, quercetin-3-O-beta-D-glucopyranoside, luteolin-7-O-beta-D-glucuronide, apigenin-7-O-beta-D-glucuronide, quercetin, tribuloside, and apigenin. The method involves the use of a Hypersil octadecylsilyl silica (ODS) analytical column (125A, 5 microm, 4.6 x 250 mm) at 25 degrees C with the mixture of acetonitrile and aqueous H(3)PO(4) as the mobile phase and detection at 254 nm. The recovery of the method is 95.4-104.8%, and linearity (r > 0.9998) is obtained for all the flavonoids. The results indicate that the flavonoid content of P. multifida varied significantly from locality to locality.     

Analysis of antioxidant flavonoids from asteraceae and moraceae plants by capillary electrophoresis

Summary Antioxidant flavonoids from the plantsSolidago gigantea Ait.,Taraxacum officinale Wiggers and Webers (Asteraceae) andMorus nigra L. (Moraceae) have been analysed by capillary electrophoresis (CE).Solidago gigantea was investigated because of its diuretic, spasmolytic, antiphlogistic, and wound-healing effect,Taraxacum officinale because it has been shown to have good diuretic and choleretic activity, andMorus nigra because it is also widely regarded as a diuretic and antidiabetic agent. Aqueous and methanolic extracts of these plants have antioxidant properties. Because their flavonoid composition might be important in their free-radical-scavenging activity, a capillary electrophoretic method was developed for characterization of the flavonoids present. We identified quercetin-3-O-β-rutinoside (rutin), quercetin-3-O-β-d-glucoside (isoquercitrin), and chlorogenic acid as the most abundant compounds inSolidago gigantea andMorus nigra, and apigenin-7-O-β-glucoside, luteolin-7-O-β-glucoside, and chlorogenic acid inTaraxacum officinale. We also discovered that quercetin-3-O-α-rhamnoside (quercitrin) and quercetin-3-O-β-galactoside (hyperoside) were absent from our sample ofSolidago gigantea and quercitrin fromMorus nigra. Quantitative analysis of these extracts was performed by high-performance liquid chromatography (HPLC). Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001     

Simultaneous determination of vitexin-2"-O-glucoside, vitexin-2"-O-rhamnoside, rutin, and hyperoside in the extract of hawthorn (Crataegus pinnatifida Bge.) leaves by RP-HPLC with ultraviolet photodiode array detection

RP-HPLC with UV photodiode array detection (UV-DAD) was developed and validated for the simultaneous determination of vitexin-2"-O-glucoside, vitexin-2"-O-rhamnoside, rutin, and hyperoside in the extract of hawthorn (Crataegus pinnatifida Bge.) leaves. The analytes of interest were separated on a Diamonsil C18 column (250 x 4.6 mm id, 5 microm) with the mobile phase consisting of THF/ACN/methanol/ 0.05% phosphoric acid solution (pH 5.0) (18:1:1:80 v/vl/v). The flow rate was set at 1.0 mL/min and the eluent was detected at 340 nm for the four flavonoids. The method was linear over the studied range of 1.00-100 microg/mL for the four analytes of interest with the correlation coefficient for each analyte greater than 0.999. The LOD and LOQwere 0.03 and 0.10 microg/mL, 0.03 and 0.10 microg/mL, 0.05 and 0.15 pg/mL, 0.10 and 0.30 microg/mL for vitexin-2"-O-glucoside, vitexin-2"-0-rhamnoside, rutin, and hyperoside, respectively. The optimized method was successfully applied to the analysis of four important flavonoids in the extract of hawthorn leaves. The total amounts of the four flavonoids were 22.2, 62.3, 4.27, and 8.24 mg/g dry weight for vitexin-2"-O-glucoside, vitexin-2"-O-rhamnoside, rutin, and hyperoside in the extract of hawthorn leaves, respectively.     

Rapid and simple method for screening of natural antioxidants from Chinese herb Flos Lonicerae Japonicae by DPPH-HPLC-DAD-TOF/MS

A rapid and simple method has been developed for the screening and identification of natural antioxidants of Flos Lonicerae Japonicae (FLJ), derived from the flower buds of Lonicera japonica. The hypothesis is that upon reaction with 1,1-diphenyl-2-picrylhydrazyl (DPPH), the peak areas (PAs) of compounds with potential antioxidant effects in the HPLC chromatograms will be significantly reduced or disappeared, and the identity confirmation could be achieved by HPLC-DAD-TOF/MS hyphenated technique. Using the proposed approach, about 14 compounds in the FLJ extract were found to possess a potential antioxidant activity. They were identified as chlorogenic acid (1), 1-O-caffeoylquinic acid (1-O-CQA, 2), caffeic acid (4), 4-O-CQA (5), rutin (7), isoquercitrin (8), luteolin-7-O-glucoside (9), lonicerin (10), 4,5-O-dicaffeoylquinic acid (4,5-O-diCQA, 11), 3,5-O-diCQA (12), 1,3-O-diCQA (13), 3,4-O-diCQA (14), 1,4-O-diCQA (16), and luteolin (17). In addition, the free radical scavenging capacities of the available identified compounds were also investigated by HPLC assay. The results indicated that the compounds with PAs significantly decreasing were natural antioxidants, whereas those with PAs not changing presented no activities, which accordingly indicated that this newly proposed method could be widely applied for rapid screening and identification of natural antioxidants from complex matrices including Chinese herbal medicines.     

Chemical composition and antioxidant activity of Campanula alliariifolia

In this study, the chemical constituents of Campanula alliariifolia Willd. (Campanulaceae) are being investigated for the first time with the aid of this article. Five known compounds, which were quercetin-3-O-glucoside, quercetin-3-O-rutinoside, kaempferol-3-O-glucoside, lobetyolin (9-O-beta-D-glucopyranosyl-2,10-tetradecadien-4,6-diyne-8,14-diol) and lobetyol (2,10-tetradecadien-4,6-diyne-8,9,14-triol), were isolated from the methanol extract. The antioxidant activity of the methanol extract and the purified compounds of the plant was investigated with DPPH (1,1-diphenyl-picrilyhydrazyl) (free radical scavenging activity) and reducing power methods. The methanol extract has antioxidant capacity according to the mentioned methods. Lobetyol and lobetyolin showed significant antioxidant activity more than both methanol extract and other purified compounds.     

Capillary electrochromatography of selected phenolic compounds of Chamomilla recutita

This article explores the use of capillary electrochromatography for the analysis of chamomile (Chamomilla recutita L.) extracts. After a thorough study of analytical parameters such as mobile and stationary phase composition, applied voltage, and temperature, a methodology to determine 11 bioactive phenolic compounds (coumarins: herniarin, umbelliferone; phenylpropanoids: chlorogenic acid, caffeic acid; flavones: apigenin, apigenin-7-O-glucoside, luteolin, luteolin-7-O-glucoside; flavonols: quercetin, rutin and flavanone: naringenin) in chamomile extracts was proposed. The method was performed in a Hypersil SCX/C18 column with pH 2.8 phosphate buffer at 50 mmol L(-1) containing 50% acetonitrile (pH adjusted before the addition of the organic solvent). All compounds were separated in less than 7.5 min under isocratic conditions. Figures of merit include linearity (peak area versus apigenin concentration) from 50.0-1000 microg/mL (r2=0.995), and intra-day precision of retention time and peak area better than 1.3% CV and 15%, respectively. The limits of detection and quantification for apigenin were 35.0 microg/mL and 150.0 microg/mL, respectively. This article also describes an NMR 1H study, carried out to monitor a new clean-up procedure for extracts containing propyleneglycol, whose components are poorly retained in conventional octadecyl silica cartridges.     

Determination of quercetin and its glucosides in onion by electrochemical methods

Quercetin (Q), quercetin-3,4'-diO-beta-glucoside (Q3,4'G), quercetin-3-O-beta-glucoside (Q3G) and quercetin-4'-O-beta-glucoside (Q4'G) were determined in onion bulbs (Allium cepa) by HPLC with amperometric detection after analysis of the hydrodynamic voltammograms of flavonoid standards within the potential range of 50-1000 mV and by cyclic voltammetry (CV) method. The hydrodynamic voltammetric profiles of flavonoids showed that the peak current of Q, Q3G, Q4'G and Q3,4'G increased rapidly when the applied potential exceeded +450 mV (vs. SCE). High sensitivity and low background current were observed at the applied potential of +950 mV (vs. SCE). The lower limits of detection (LOD) were determined at signal-to-noise ratio of 3 and showed the following values: 8.05x10(-8)M (Q), 1.08x10(-7) M (Q3G), 1.22x10(-7) M (Q4'G) and 2.6x10(-7) M (Q3,4'G). The data provided by HPLC-UV-MS confirmed the presence of Q, Q3G, Q4'G and Q3,4'G in 80% methanol extracts of lyophilised onion bulbs. The CV method was applied for the qualitative assessment of onion flavonoids followed by the determination of anodic peak potential (E(a)) of the standards. The qualitative analysis of onion flavonoids was based on the anodic peak current (I(a)) of the extracts after external standards addition. The recorded cyclic voltammograms of the above flavonoid standards showed that all four compounds had well-defined oxidation waves with peak potentials of 310, 390, 482 and 800 mV (vs. Ag/AgCl) for Q, Q3G, Q4'G and Q3,4'G in 50 mM acetate-acetic buffer (pH 5.5) in 80% methanol, respectively. The study proved applicability of the CV method for identifying Q, Q3G, Q4'G and Q3,4'G in onion.     

Analysis of flavonoid constituents from leaves of Acanthopanax senticosus harms by electrospray tandem mass spectrometry

Three known flavonoids, quercetin, quercitrin (quercetin-3-0-rhamnoside) and rutin (quercetin-3-0 rutinoside), have been identified for the first time in the leaves of Acanthopanax senticosus Harms by using electrospray tandem mass spectrometry techniques (ESI-MS(n)). The flavonoid hyperin (quercetin-3-0-beta-galactoside), already known to be present, was also investigated. The diagnostic fragment ions of the aglycone quercetin were obtained in the ESI-MS(n) experiments, and a fragmentation mechanism proposed.     

Fast chromatographic separation for the quantitation of the main flavone dyes in Reseda luteola (weld)

In the past decades, there has been a renewed interest in the use of natural dye plants for textile dyeing, e.g. Reseda luteola (weld). Its main yellow dye constituents are the flavones luteolin-7,3'-O-diglucoside, luteolin-7-O-glucoside and luteolin. The aim of this work was to develop a simple validated industrially usable quantitative method to assess the flavone content of R. luteola samples. The flavones were overnight extracted from the dried and ground aerial parts of the plant at room temperature via maceration with methanol-water 8:2. Afterwards, they were quantified through internal standardisation against chrysin by RP-HPLC-UV at 345 nm. The efficiency of the one-step extraction was 95%. The limits of detection (LOD) and quantitation (LOQ) were ≤ 1 ng and ≤ 3 ng, respectively, providing ample sensitivity for the purpose. The precision expressed as relative standard deviation of the entire method was <6.5% for the combined content of luteolin-7,3'-O-diglucoside, luteolin-7-O-glucoside and luteolin. The average absolute recovery (accuracy) at three spiking levels was 102% (range: 98-107%) and the relative recovery ranged from 99 to 102%. The separation was initially carried out on a traditional 250 mm × 4.6 mm 5 μm HPLC column (80 min run time, 35.9 mL MeOH). It was then speeded up by the use of a 50 mm × 3.0mm 1.8 μm UHPLC column (5 min run time, 1.4 mL MeCN), while still using a conventional HPLC system. Whereas, the retention times on the UHPLC column were relatively less reproducible, cross-validation showed that the quantitation of luteolin-7,3'-O-diglucoside, luteolin-7-O-glucoside and luteolin was not statistically significantly different, with comparable precision. The method using the UHPLC column is more sensitive. The analytical method described meets the demand for a very small manpower input per sample and uses standard laboratory equipment. Usage of short UHPLC columns opens up interesting possibilities for modernising HPLC-based phytochemical analyses.