Application of accelerated solvent extraction coupled with high-performance counter-current chromatography to extraction and online isolation of chemical constituents from Hypericum perforatum L

Multi-dimensional preparation of Thymus quinquecostatus Celak. by normal-phase flash chromatography coupled to counter-current chromatography

In this study, a multi-dimensional chromatography system was developed by integrating normal-phase flash chromatography and counter-current chromatography to isolate flavonoids, phenylpropanoids, and thymol from the aerial parts of Thymus quinquecostatus Celak. In the online multi-dimensional switching system, a normal-phase flash chromatograph packed with 1.2 g of dry homogeneous silica gel mixture (containing 600 mg of methanol extract) was connected to counter-current chromatography via a six-port valve. Two two-dimensional separations were performed using n-heptane-ethyl acetate-methanol-water (6:4:6:4, v/v) and ethyl acetate-water solvent systems sequentially to separate the constituents of Thymus quinquecostatus Celak. The upper phase of the former solvent system was utilized as both elution solvent for flash chromatography and the stationary phase for counter-current chromatography, while the lower phase of the latter solvent system containing 10 mM trifluoroacetic acid was employed as elution solvent for flash chromatography and one mobile phase in pH gradient counter-current chromatography. Thymol (7) and xanthomicrol (8), two hydrophobic ingredients, were purified in the initial two-dimensional separation. The subsequent two-dimensional separation yielded six hydrophilic compounds, namely dihydrokaempferol-7-O-D-glucopyranoside (1), lithospermic acid (2), luteolin-7-O-glucuronide (3), rosmarinic acid (4), messerschmidin (5) and apigenin-7-O-D-glucuronide (6). This study represents the first documented use of online multi-dimensional normal-phase flash chromatography coupled to counter-current chromatography for separating constituents from Thymus quinquecostatus Celak.

Valeriana rigida Ruiz & Pav. Root Extract: A New Source of Caffeoylquinic Acids with Antioxidant and Aldose Reductase Inhibitory Activities

Valeriana rigida Ruiz & Pav. (V. rigida) has long been used as a herbal medicine in Peru; however, its phytochemicals and pharmacology need to be scientifically explored. In this study, we combined the offline 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH)-/ultrafiltration-high-performance liquid chromatography (HPLC) and high-speed counter-current chromatography (HSCCC)/pH-zone-refining counter-current chromatography (pH-zone-refining CCC) to screen and separate the antioxidants and aldose reductase (AR) inhibitors from the 70% MeOH extract of V. rigida, which exhibited remarkable antioxidant and AR inhibitory activities. Seven compounds were initially screened as target compounds exhibiting dual antioxidant and AR inhibitory activities using DPPH-/ultrafiltration-HPLC, which guided the subsequent pH-zone-refining CCC and HSCCC separations of these target compounds, namely 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, 5-O-caffeoylquinic acid, 3,4-O-di-caffeoylquinic acid, 3,5-O-di-caffeoylquinic acid, 4,5-O-di-caffeoylquinic acid, and 3,4,5-O-tri-caffeoylquinic acid. These compounds are identified for the first time in V. rigida and exhibited remarkable antioxidant and AR inhibitory activities. The results demonstrate that the method established in this study can be used to efficiently screen and separate the antioxidants and AR inhibitors from natural products and, particularly, the root extract of V. rigida is a new source of caffeoylquinic acids with antioxidant and AR inhibitory activities, and it can be used as a potential functional food ingredient for diabetes.

MeJA Elicitation of Chicory Hairy Roots Promotes Efficient Increase of 3,5-diCQA Accumulation, a Potent Antioxidant and Antibacterial Molecule

Cichorium intybus L. (Asteraceae) is an important industrial crop, as well as a medicinal plant which produces some bioactive compounds implicated in various biological effects with potential applications in human health. Particularly, roots produce hydroxycinnamic acids like 5-caffeoyquinic acid and 3,5-dicaffeoylquinic acid (di-CQA). The present investigation relates to the use of methyl jasmonate for enhancing phenolic compounds accumulation and production in hairy root cultures of C. intybus. Elicitated hairy root growth rate increased 13.3 times compared with the initial inoculum in a period of 14 days and di-CQA production represented about 12% of DW. The elicitation has also promoted the production of tricaffeoylquinic acid never described in the chicory roots and identified as 3,4,5-tricaffeoyquinic acid by means of nuclear magnetic resonance. Our study confirmed the strong anti-oxidant effect of di-CQA. Our results also confirmed globally a selectivity of action of di-CQA against Gram-positive bacteria, in particular against some strains of Staphylococcus and Streptococcus. However, a non-negligible antibacterial activity of di-CQA against Pseudomonas aeruginosa was also underlined (MIC = 0.156 mg.mL⁻¹ against some P. aeruginosa strains). The influence of di-CQA has been explored to evaluate its impact on the physiology of P. aeruginosa. Di-CQA showed no effect on the biofilm formation and the production of extracellular pyocyanin. However, it demonstrated an effect on virulence through the production of pyoverdine with a dose-dependent manner by more than 7-fold when treated at a concentration of 128 µg·mL⁻¹, thus suggesting a link between di-CQA and iron sequestration. This study shows that elicitated hairy root cultures of chicory can be developed for the production of di-CQA, a secondary metabolite with high antibacterial potential.

Optimized and Validated HPLC Analysis of St. John's Wort Extract and Final Products by Simultaneous Determination of Major Ingredients

Aim of this work was to develop a validated high performance liquid chromatography method for the analysis of extracts and final products of St. John's wort, according to international guidelines for bioanalytical method validation. Chromatographic separation was performed on a C18 column with a combination of gradient and isocratic steps; the mobile phase composed of ammonium acetate solution (pH 4.5; 10 mM), acetonitrile and methanol. Quantification and method validation was performed using extract spiked with external reference standards of chlorogenic acid, rutin, hyperoside, isoquercitrin, quercetin and hypericin. Validation study revealed that trans-chlorogenic acid is partially transformed into its cis-isomer during analysis. The method showed good linearity, precision and accuracy. Hyperforin was completely unstable. All other ingredients were stable at -18°C and after three freeze-thaw cycles, while stability of most ingredients was limited at room temperature and 4 - 8°C; quercetin was the most unstable one. The major ingredients of methanolic extracts, infusions and final products of Hypericum perforatum were completely resolved and quantified. Beyond its potential usefulness in the analysis of St. John's wort products, this study addresses the issue of validation from the perspective of the field of bioanalysis and reveals the wealth of critical information which can be derived.

Evaluation of phenolic profile, enzyme inhibitory and antimicrobial activities of Nigella sativa L. seed extracts

Black cumin (Nigella sativa L. [N.sativa]) seed extracts demonstrated numerous beneficial biological effects including, among others, antidiabetic, anticancer, immunomodulatory, antimicrobial, anti-inflammatory, antihypertensive, and antioxidant activity. To better understand the phytochemical composition of N. sativa seeds, methanol seed extracts were analyzed for phenolic acid and flavonoid content. Furthermore, we tested N. sativa methanol, n-hexane, and aqueous seed extracts for their inhibitory activity against butyrylcholinesterase (BChE) and catalase (CAT) as well as for antimicrobial activity against several bacterial and a yeast strains. The phenolic content of N. sativa was analyzed using ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). The inhibition of BChE was assessed by modified Ellman's method, and the inhibition of CAT was determined by monitoring hydrogen peroxide consumption. The extracts were tested against Bacillus subtilis, Staphylococcus aureus, Salmonella enterica, and Escherichia coli using the agar diffusion method. The UHPLC-MS/MS method allowed the identification and quantification of 23 phenolic compounds within 15 minutes. The major components found in N. sativa seed extract were sinapinic acid (7.22 ± 0.73 µg/mg) as a phenolic acid and kaempferol (11.74 ± 0.92 µg/mg) as a flavonoid. All extracts showed inhibitory activity against BChE, with methanol seed extract demonstrating the highest inhibitory activity (inhibitory concentration 50% [IC50] 79.11 ± 6.06 µg/ml). The methanol seed extract also showed strong inhibitory activity against CAT with an IC50 value of 6.61 ± 0.27 µg/ml. Finally, the methanol extract exhibited considerable inhibitory activity against the tested microbial strains. Overall, this is the first study to investigate the ability of black cumin seed extracts to inhibit CAT. Our results indicate that N. sativa seed can be considered as an effective inhibitor of CAT activity.

Analysis of lignans in Magnoliae Flos by turbulent flow chromatography with online solid-phase extraction and high-performance liquid chromatography with tandem mass spectrometry

In this study, a method coupling turbulent flow chromatography with online solid-phase extraction and high-performance liquid chromatography with tandem mass spectrometry was developed for analyzing the lignans in Magnoliae Flos. By the online pretreatment of turbulent flow chromatography solid-phase extraction, the impurities removal and analytes concentration were automatically processed, and the lignans were separated rapidly and well. Seven lignans of Magnoliae Flos including epieudesmin, magnolin, 1-irioresinol-B-dimethyl ether, epi-magnolin, fargesin aschantin, and demethoxyaschantin were identified by comparing their retention behavior, UV spectra, and mass spectra with those of reference substances or literature data. The developed method was validated, and the good results showed that the method was not only automatic and rapid, but also accurate and reliable. The turbulent flow chromatography with online solid-phase extraction and high-performance liquid chromatography with tandem mass spectrometry method holds a high potential to become an effective method for the quality control of lignans in Magnoliae Flos and a useful tool for the analysis of other complex mixtures.

How to eliminate the formation of chlorogenic acids artefacts during plants analysis? Sea sand disruption method (SSDM) in the HPLC analysis of chlorogenic acids and their native derivatives in plants

The analytical procedures for determining plant constituents involve the application of sample preparation methods to fully isolate and/or pre-concentrate the analyzed substances. High-temperature liquid extraction is still applied most frequently for this purpose. The present paper shows that high-temperature extraction cannot be applied for the analysis of chlorogenic acids (CQAs) and their derivatives in plants as it causes the CQAs transformation leading to erroneous quantitative estimations of these compounds. Experiments performed on different plants (black elder, hawthorn, nettle, yerba maté, St John's wort and green coffee) demonstrate that the most appropriate method for the estimation of CQAs/CQAs derivatives is sea sand disruption method (SSDM) because it does not induce any transformation and/or degradation processes in the analyzed substances. Owing to the SSDM method application we found that the investigated plants, besides four main CQAs, contain sixteen CQAs derivatives, among them three quinic acids. The application of SSDM in plant analysis not only allows to establish a true concentration of individual CQAs in the examined plants but also to determine which chlorogenic acids derivatives are native plant components and what is their concentration level. What is even more important, the application of SSDM in plant analysis allows to eliminate errors that may arise or might have arisen in the study of chlorogenic acids and their derivatives in plant metabolism.

Countercurrent Separation of Natural Products: An Update

This work assesses the current instrumentation, method development, and applications in countercurrent chromatography (CCC) and centrifugal partition chromatography (CPC), collectively referred to as countercurrent separation (CCS). The article provides a critical review of the CCS literature from 2007 since our last review (J. Nat. Prod. 2008, 71, 1489-1508), with a special emphasis on the applications of CCS in natural products research. The current state of CCS is reviewed in regard to three continuing topics (instrumentation, solvent system development, theory) and three new topics (optimization of parameters, workflow, bioactivity applications). The goals of this review are to deliver the necessary background with references for an up-to-date perspective of CCS, to point out its potential for the natural product scientist, and thereby to induce new applications in natural product chemistry, metabolome, and drug discovery research involving organisms from terrestrial and marine sources.

Ultrasound-assisted dynamic extraction coupled with parallel countercurrent chromatography for simultaneous extraction, purification, and isolation of phytochemicals: application to isoflavones from red clover

A novel procedure comprising ultrasonic-assisted dynamic extraction (UADE) coupled with two countercurrent-chromatography systems (parallel countercurrent chromatography, PCCC) was developed. This technique offers the possibility for simultaneous extraction, solvent configuration, purification, and isolation of target compounds. This new approach was applied to the fractionation and purification of isoflavones from red clover. The two-phase solvent system was prepared by automating the equipment. The lower aqueous phase of the two-phase solvent system was used as the UADE solution and as the mobile phase for PCCC. After the extraction and purification steps, the purified sample was pumped into the countercurrent chromatography 1 (CCC1) column for the first isolation step. During CCC1 separation, the sample was enriched and purified and then pumped into the CCC2 column for the second isolation step. After completion of the first cycle of UADE-PCCC steps, the second-cycle experiments were performed. Using this sequence, five target compounds, daidzein, prunetin, genistein, irilone, and maackiain, with >95.31 % purity were successfully extracted and isolated using the two-phase solvent system of n-hexane-ethyl acetate-ethanol-water (0.623:1.00:0.99:1.246, v/v). With this instrumental setup, scientific and systematic extraction and isolation of natural products was achieved, and this technique has great potential for industrial application. Graphical Abstract Simplified schematic of instrumental setup of UADE combined with two HSCCC instruments.

Isolation of mono-caffeoylquinic acids from tobacco waste using continuous resin-based pre-separation and preparative HPLC

Three isomers of mono-caffeoylquinic acid, specifically, 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid and 5-O-caffeoylquinic acid, were successfully isolated from a crude extract of tobacco (Nicotiana tobaccum L.) wastes using continuous resin-based pre-separation and preparative high-performance liquid chromatography (HPLC). The extract of tobacco wastes was continuously pre-separated by resin-based columns packed with D101 and XAD-4, yielding total mono-caffeoylquinic acids with a purity of 67.71% and a recovery rate of 90.06%. Variables affecting resolution and productivity of three mono-caffeoylquinic acid isomers in preparative HPLC (i.e. mobile-phase composition, pH, flow rate and loading amount) were studied. The optimum chromatographic conditions were determined to be a mobile phase consisting of 15% (v/v) methanol and aqueous acetic acid with a pH of 4.5, a flow rate of 4.0 mL/min, a loading amount of 4 mL and a detection wavelength of 360 nm. From 300 mg of loading sample, 56.3 mg of 3-O-caffeoylquinic acid, 92.8 mg of 5-O-caffeoylquinic acid and 73.1 mg of 4-O-caffeoylquinic acid were obtained in a single run, each with a purity of over 98% by HPLC. The structures of the isolated compounds were elucidated by ESI-MS, (1) H-NMR and (13) C-NMR spectral data.

Response surface modeling and optimization of accelerated solvent extraction of four lignans from fructus schisandrae

A new method based on accelerated solvent extraction (ASE) combined with response surface methodology (RSM) modeling and optimization has been developed for the extraction of four lignans in Fructus Schisandrae (the fruits of Schisandra chinensis Baill). The RSM method, based on a three level and three variable Box-Behnken design (BBD), was employed to obtain the optimal combination of extraction condition. In brief, the lignans schizandrin, schisandrol B, deoxyschizandrin and schisandrin B were optimally extracted with 87% ethanol as extraction solvent, extraction temperature of 160 °C, static extraction time of 10 min, extraction pressure of 1,500 psi, flush volume of 60% and one extraction cycle. The 3D response surface plot and the contour plot derived from the mathematical models were applied to determine the optimal conditions. Under the above conditions, the experimental value of four lignans was 14.72 mg/g, which is in close agreement with the value predicted by the model.