Dexmedetomidine Alleviates Abdominal Aortic Aneurysm by Activating Autophagy Via AMPK/mTOR Pathway.

BACKGROUND: Abdominal aortic aneurysms (AAA) are a critical global health issue with increasing prevalence. Dexmedetomidine (DEX) is a highly selective α2-adrenoceptor agonist that has previously been shown to play a protective role in AAA. Nevertheless, the mechanisms underlying its protection effect remain not fully understood. METHODS: A rat AAA model was established via intra-aortic porcine pancreatic elastase perfusion with or without DEX administration. The abdominal aortic diameters of rats were measured. Hematoxylin-eosin and Elastica van Gieson staining were conducted for histopathological observation. TUNEL and immunofluorescence staining were utilized to detect cell apoptosis and α-SMA/LC3 expression in the abdominal aortas. Protein levels were determined using western blotting. RESULTS: DEX administration repressed the dilation of aortas, alleviated pathological damage and cell apoptosis, and suppressed phenotype switching of vascular smooth muscle cells (VSMCs). Moreover, DEX activated autophagy and regulated the AMP-activated protein kinase/mammalian target of the rapamycin (AMPK/mTOR) signaling pathway in AAA rats. Administration of the AMPK inhibitor attenuated the DEX-mediated ameliorative effects on AAA in rats. CONCLUSION: DEX ameliorates AAA in rat models by activating autophagy via the AMPK/mTOR pathway.

Highly Activated Neuronal Firings Monitored by Implantable Microelectrode Array in the Paraventricular Thalamus of Insomnia Rats.

Insomnia is a common sleep disorder around the world, which is harmful to people's health, daily life, and work. The paraventricular thalamus (PVT) plays an essential role in the sleep-wake transition. However, high temporal-spatial resolution microdevice technology is lacking for accurate detection and regulation of deep brain nuclei. The means for analyzing sleep-wake mechanisms and treating sleep disorders are limited. To detect the relationship between the PVT and insomnia, we designed and fabricated a special microelectrode array (MEA) to record electrophysiological signals of the PVT for insomnia and control rats. Platinum nanoparticles (PtNPs) were modified onto an MEA, which caused the impedance to decrease and improved the signal-to-noise ratio. We established the model of insomnia in rats and analyzed and compared the neural signals in detail before and after insomnia. In insomnia, the spike firing rate was increased from 5.48 ± 0.28 spike/s to 7.39 ± 0.65 spike/s, and the power of local field potential (LFP) decreased in the delta frequency band and increased in the beta frequency band. Furthermore, the synchronicity between PVT neurons declined, and burst-like firing was observed. Our study found neurons of the PVT were more activated in the insomnia state than in the control state. It also provided an effective MEA to detect the deep brain signals at the cellular level, which conformed with macroscopical LFP and insomnia symptoms. These results laid the foundation for studying PVT and the sleep-wake mechanism and were also helpful for treating sleep disorders.

Isolation and purification of two antioxidant isomers of resveratrol dimer from the wine grape by counter-current chromatography.

Resveratrol dimers belong to a group of compounds called stilbenes, which along with proanthocyanidins, anthocyanins, catechins, and flavonols are natural phenolic compounds found in grapes and red wine. Stilbenes have a variety of structural isomers, all of which exhibit various biological properties. Counter-current chromatography with a two-phase solvent system composed of n-hexane/ethyl acetate/methanol/water (2:5:4:5, v/v/v/v) was applied to isolate and purify stilbene from the stems of wine grape. Two isomers of resveratrol dimers trans-ε-viniferin and trans-δ-viniferin were obtained from the crude sample in a one-step separation, with purities of 93.2 and 97.5%, respectively, as determined by high-performance liquid chromatography. The structures of these two compounds were identified by (1) H and (13) C NMR spectroscopy. In addition, their antioxidant activities were assessed by 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The antioxidant activities of trans-δ-viniferin were higher than that of trans-ε-viniferin in this model. This work demonstrated that counter-current chromatography is a powerful and effective method for the isolation and purification of polyphenols from wine grape. Additionally, the DPPH radical assay showed that the isolated component trans-δ-viniferin exhibited stronger antioxidant activities than trans-ε-viniferin and a little bit weaker than vitamin E at the same concentration.

High-Throughput Microelectrode Arrays for Precise Functional Localization of the Globus Pallidus Internus.

The globus pallidus internus (GPi) was considered a common target for stimulation in Parkinson's disease (PD). Located deep in the brain and of small size, pinpointing it during surgery is challenging. Multi-channel microelectrode arrays (MEAs) can provide micrometer-level precision functional localization, which can maximize the surgical outcome. In this paper, a 64-channel MEA modified by platinum nanoparticles with a detection site impedance of 61.1 kΩ was designed and prepared, and multiple channels could be synchronized to cover the target brain region and its neighboring regions so that the GPi could be identified quickly and accurately. The results of the implant trajectory indicate that, compared to the control side, there is a reduction in local field potential (LFP) power in multiple subregions of the upper central thalamus on the PD-induced side, while the remaining brain regions exhibit an increasing trend. When the MEA tip was positioned at 8,700 µm deep in the brain, the various characterizations of the spike signals, combined with the electrophysiological characteristics of the ß-segmental oscillations in PD, enabled MEAs to localize the GPi at the single-cell level. More precise localization could be achieved by utilizing the distinct characteristics of the internal capsule (ic), the thalamic reticular nucleus (Rt), and the peduncular part of the lateral hypothalamus (PLH) brain regions, as well as the relative positions of these brain structures. The MEAs designed in this study provide a new detection method and tool for functional localization of PD targets and PD pathogenesis at the cellular level.

Perioperative use of immersive head-mounted virtual reality display enhances patient satisfaction in great saphenous vein surgery: a single-center clinical observation study.

OBJECTIVE: To explore the application effect of head-mounted virtual reality display immersive experience in improving the perioperative satisfaction of patients undergoing great saphenous vein surgery. METHODS: A total of 158 patients undergoing saphenous vein surgery at the First Affiliated Hospital, Jiangxi Medical College, Nanchang University from January 2020 to January 2023 were randomly divided into an observation group and a control group in a 1:1 ratio, with 79 cases in each group. The observation group received head-mounted display virtual reality immersive experience, whereas the control group received midazolam. The study compared the perioperative satisfaction, changes in preoperative and postoperative anxiety and depression scores, intraoperative blood pressure and heart rate, postoperative visual analog scale (VAS) score, and the incidence of postoperative nausea and vomiting between the two groups. Additionally, the satisfaction of patients, anesthesiologists, and chief surgeons was compared. RESULTS: All surgeries were completed successfully. Patients in the observation group exhibited higher perioperative satisfaction compared to those in the control group (P<0.001). There were no significant differences in anxiety or depression scores between the two groups before surgery (P>0.05). However, both groups showed a reduction in anxiety and depression scores postoperatively, with the observation group demonstrating lower scores than the control group (both P<0.05). The observation group also had lower intraoperative blood pressure, heart rate, postoperative VAS scores, and incidence of nausea and vomiting compared to the control group (all P<0.05). Furthermore, the satisfaction levels of the anesthesiologists and chief surgeons were higher in the observation group than in the control group (P=0.043, 0.012). CONCLUSION: Head-mounted display virtual reality immersive experience can enhance perioperative satisfaction among patients undergoing great saphenous vein surgery, reduce anxiety and depression scores, and contribute to the stabilization of hemodynamics during surgery, thereby decreasing postoperative nausea and vomiting.

SWCNTs/PEDOT:PSS nanocomposites-modified microelectrode arrays for revealing locking relations between burst and local field potential in cultured cortical networks.

Burst and local field potential (LFP) are fundamental components of brain activity, representing fast and slow rhythms, respectively. Understanding the intricate relationship between burst and LFP is crucial for deciphering the underlying mechanisms of brain dynamics. In this study, we fabricated high-performance microelectrode arrays (MEAs) using the SWCNTs/PEDOT:PSS nanocomposites, which exhibited favorable electrical properties (low impedance: 12.8 ± 2.44 kΩ) and minimal phase delay (-11.96 ± 1.64°). These MEAs enabled precise exploration of the burst-LFP interaction in cultured cortical networks. After a 14-day period of culture, we used the MEAs to monitor electrophysiological activities and revealed a time-locking relationship between burst and LFP, indicating the maturation of the neural network. To further investigate this relationship, we modulated burst firing patterns by treating the neural culture with increasing concentrations of glycine. The results indicated that glycine effectively altered burst firing patterns, with both duration and spike count increasing as the concentration rose. This was accompanied by an enhanced level of time-locking between burst and LFP but a decrease in synchrony among neurons. This study not only highlighted the pivotal role of SWCNTs/PEDOT:PSS-modified MEAs in elucidating the interaction between burst and LFP, bridging the gap between slow and fast brain rhythms in vitro but also provides valuable insights into the potential therapeutic strategies targeting neurological disorders associated with abnormal rhythm generation.

Experimental Study on Different Improvement Schemes of EICP-Lignin Solidified Silt.

In practical engineering applications, silt is prone to liquefaction and quicksand. This paper mainly studies the improvement effects of urease, lignin and their mixture on the strength and liquefaction resistance of silt. Based on the results and phenomena of an unconfined compressive strength and dynamic triaxial test, the improvement effects of the compressive strength, deformation resistance and liquefaction resistance of silt under different improvement schemes are analyzed, and the optimal values of the cement or lignin when enzyme-induced calcium carbonate precipitation (EICP) technology, lignin alone or EICP and lignin are obtained. The results show that the optimum concentration of the constant temperature and humidity sample (referred to as the constant humidity sample) and the constant temperature immersion sample (referred to as the soaking sample) of urease in the unconfined compressive strength test is 1.0 mol/L, and the compressive strength of the soaking sample is 4.9 MPa, which is 1.56 times that of the constant humidity sample; the optimum addition ratio of the lignin-improved constant humidity sample is 3%, and its compressive strength is 2.07 Mpa; the optimum addition ratio of the samples immersed at constant temperature is 4%, and the compressive strength is 3.05 MPa; when urease combines with lignin to improve silt, 4% is the best lignin addition ratio, the compressive strength of the constant humidity sample reaches 1.57 Mpa and the compressive strength of the soaking sample reaches 3.75 MPa; in the dynamic triaxial multi-stage cyclic load test, all samples were cured at constant humidity sample, and in the urease modified silt scheme, 1.0 mol/L was the optimal cement concentration; in the scheme of improving silt with lignin, 3% is the optimal addition ratio; when 1.25 mol/L cementation solution plus urease crude extract is combined with different ratios of lignin in the experimental scheme, 3% is the best lignin addition ratio.

Risk Perception and Public Pandemic Fatigue: The Role of Perceived Stress and Preventive Coping.

Purpose: This study explores the status of pandemic fatigue, predictors, and their mechanisms of action based on a stress-response framework and a parallel model of future-oriented response. Patients and methods: Study 1 investigated 8426 Chinese adult residents' understanding of and willingness to cooperate with the pandemic prevention and control policies and Study 2 surveyed 1635 Chinese residents on their activeness of pandemic prevention and control (APPC), pandemic risk perception, perceived stress, and future-oriented coping. Results: Study 1 found that public understanding of and willingness to cooperate with prevention policies were significantly lower in 2022 than in 2020 and 2021. Study 2 found that risk perception negatively predicted the APPC; perceived stress and preventive coping significantly mediated the relationship between risk perception and APPC; but perceived stress and proactive coping did not significantly mediate the relationship between risk perception and APPC. Conclusion: This revealed an increase in public fatigue in the third year of the pandemic. Pandemic fatigue can be predicted by pandemic risk perception, but the direct pathway of action is not significant and requires the mediation of perceived stress and preventive coping.

Dexmedetomidine protects cells from Angiotensin II-induced smooth muscle cell phenotype switch and endothelial cell dysfunction.

Abdominal aortic aneurysm (AAA) is a vascular disorder greatly threatening life of the elderly population. Dexmedetomidine (DEX), an α2-adrenergic receptor agonist, has been shown to suppress AAA development. Nevertheless, the signaling pathways that might be mediated by DEX in AAA has not been clarified. Vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) were treated with Angiotensin II (Ang II) to mimic AAA in vitro. BrdU, wound healing, and Transwell assays were utilized for measuring VSMC proliferation and migration. Western blotting was used for evaluating protein levels of contractile VSMC markers, collagens and matrix metalloproteinases (MMPs) in VSMCs as well as apoptosis- and HMGB1/TLR4/NF-κB signaling-related markers in ECs. Cell adhesion molecule expression and monocyte-endothelial adhesion were assessed by immunofluorescence staining and adhesion assays. Flow cytometry was implemented for analyzing EC apoptosis. Hematoxylin-eosin staining and ELISA were used to detect the effect of DEX in vivo. In this study, DEX inhibited Ang II-evoked VSMC phenotype switch and extracellular matrix degradation. DEX suppressed the inflammatory response and apoptosis of ECs induced by Ang II. DEX inhibited HMGB1/TLR4/NF-κB signaling pathway in Ang II-treated ECs. DEX attenuated Ang II-induced AAA and inflammation in mice. Overall, DEX ameliorates Ang II-induced VSMC phenotype switch, and inactivates HMGB1/TLR4/NF-κB signaling pathway to alleviate Ang II-induced EC dysfunction.

Simultaneous real-time analysis of tear film optical quality dynamics and functional visual acuity in dry eye disease.

BACKGROUND: To assess the effect of tear film instability in dry eye disease (DED) by measuring visual performance and tear film optical quality in a simultaneous real-time analysis system. METHODS: Thirty-seven DED participants and 20 normal controls were recruited. A simultaneous real-time analysis system was developed by adding a functional visual acuity (FVA) channel to a double-pass system. Repeated measurements of FVA and objective scatter index (OSI) were performed simultaneously with this system under blink suppression condition for 20 s. Patient-reported symptoms was evaluated using the Ocular Surface Disease Index (OSDI) questionnaire. Mean FVA, mean OSI, and visual acuity break-up time were defined. The OSI maintenance ratio was calculated as an evaluation index to assess the difference between dynamic OSI changes and baseline OSI. The visual maintenance ratio was also calculated in the same way. RESULTS: Moderate correlations were noted between mean OSI and FVA-related parameters (mean FVA, visual maintenance ratio, visual acuity break-up time: 0.53, - 0.56, - 0.53, respectively, P < 0.01 for all). Moderate to high correlations were noted between OSI maintenance ratio and FVA-related parameters (mean FVA, visual maintenance ratio, visual acuity break-up time: - 0.62, 0.71, 0.64, respectively, all P < 0.01). The metrics derived from the simultaneous real-time analysis system were moderately correlated with the patient-reported symptoms and the visual acuity break-up time possessed the highest correlation coefficients with OSDI total, ocular symptoms, and vision-related function (- 0.64, - 0.63, - 0.62, respectively, P < 0.01). The OSI-maintenance ratio alone appeared to exhibit the best performance of the metrics for the detection of DED with sensitivity of 95.0% and specificity of 83.8% and the combinations of FVA parameters and OSI parameters were valid and can further improve the discriminating abilities. CONCLUSIONS: OSI-related metrics were found to be potential indicators for assessing and diagnosing DED which correlated with both subjective visual performance and patient-reported symptoms; the FVA-related metrics were quantifiable indicators for evaluating visual acuity decline in DED. TRIAL REGISTRATION NUMBER: Chinese Clinical Trial Registry, ChiCTR2100051650. Registered 29 September 2021, https://www.chictr.org.cn/showproj.aspx?proj=134612.

Preliminary Application of a Continuous Functional Contrast Visual Acuity System in the Assessment of Visual Function in Dry Eye Patients.

Purpose: To investigate the feasibility and efficacy of a continuous functional contrast visual acuity (CFCVA) system in the assessment of visual function in dry eye disease (DED). Methods: Twenty patients with DED and 15 normal controls were recruited. Subjective symptoms were evaluated using the Ocular Surface Disease Index (OSDI) questionnaire, and tear film stability was assessed by a noninvasive corneal topographer. Under natural blinking conditions, the custom-built CFCVA system was used to take serial visual acuity measurements at 100%, 25%, 10%, and 5% contrast for 60 seconds. A 5-minute measurement at a 100% contrast level was defined as the stress test (ST). Mean CFCVA was defined, and visual maintenance ratio (VMR) was the ratio of mean CFCVA divided by baseline visual acuity. Results: In both groups, VMR decreased and mean CFCVA (logarithm of the minimum angle of resolution) increased with decreasing optotype contrast (from 100% to 5%). In ST, the ST VMR at the fourth and fifth minutes (VMR54 and VMR55) showed the strongest correlations with OSDI total, ocular symptoms, and vision-related function (-0.646 and -0.598, -0.688 and -0.693, and -0.599 and -0.555, respectively, P < 0.05). VMR54 and VMR55 also demonstrated the best discriminating ability for detecting DED, with areas under the curve of 0.903 and 0.867, respectively. Conclusions: Extending the continuous measuring time was more effective for detecting vision-related functional abnormalities in patients with DED than simply decreasing the optotype contrast level. Translational Relevance: The proposed CFCVA system and associated parameters offer a potential method for quantifying and interpreting the visual symptoms of DED in clinical care.

COVID-19 vaccine hesitancy and GAD: The role of risk perception and vaccination status.

Background and purpose: As Coronavirus disease (COVID-19) continues to spread around the world, COVID-19 vaccines are the most effective weapons against the global pandemic. Yet vaccine hesitancy remains a serious problem and can pose certain hazards to individuals' mental health, such as rising anxiety. Therefore, based on Self-Discrepancy Theory, this paper aims to explore the role of COVID-19 vaccine hesitancy on individual generalized anxiety disorder and its influence mechanisms through two studies. Methods: Study one involved 654 Chinese participants using the Vaccine Hesitancy Questionnaire and the Generalized Anxiety Disorder 7-item (GAD-7) scale. In Study two, the Vaccine Hesitation Questionnaire, GAD-7 scale, Perceived Risk of COVID-19 pandemic scale, and Vaccination Status Questionnaire were used and data from 3,282 Chinese residents was collected. Results: Vaccine hesitancy directly increases generalized anxiety disorder; risk perception plays a partial mediating role between vaccine hesitancy and generalized anxiety disorder; vaccination status moderated vaccine hesitancy's effect on risk perception and generalized anxiety disorder. Conclusion: Vaccine hesitancy predicts generalized anxiety disorder through risk perception, but the mediating role of risk perception is moderated by vaccination status, which means that for the vaccinated group when their vaccine hesitancy is reduced, it will be easier to reduce the risk perception and thus the generalized anxiety disorder.

Effect of social support on anxiety of medical staff one year after COVID-19 outbreak: a moderated mediating model.

One year after the outbreak of COVID-19, medical staff are facing high anxiety due to multiple work stresses. Social support has become a protective factor for healthcare workers' anxiety symptoms, but the exact mechanism of action is not yet known. Based on the buffering model, this study aims to explore the impact and mechanisms of action of healthcare workers' perception of social support (PSS) on anxiety symptoms in the context of the epidemic and to further explore how the emotional characteristics of risk perception (ECRP) and resilience play their influence. To this end, this study measured 839 healthcare workers using an online questionnaire from 4 February to 1 March 2021. The results found that PSS among healthcare workers negatively predicted anxiety symptoms. ECRP partially mediated the relationship between PSS and anxiety symptoms, and resilience moderated the first half of the pathway in the model of PSS through ECRP on anxiety symptoms. The emotional characteristics of risk perception of COVID-19 in individuals with high resilience decrease significantly with the increase of PSS, while this change is not significant in individuals with low resilience.

LC/MS guided isolation of alkaloids from lotus leaves by pH-zone-refining counter-current chromatography.

The traditional methods used in natural product separation primarily target the major components and the minor components may thus be lost during the separation procedure. Consequently, it's necessary to develop efficient methods for the preparative separation and purification of relatively minor bioactive components. In this paper, a LC/MS method was applied to guide the separation of crude extract of lotus (Nelumbo nucifera Gaertn.) leaves whereby a minor component was identified in the LC/MS analysis. Afterwards, an optimized pH-zone-refining CCC method was performed to isolate this product, identified as N-demethylarmepavine. The separation procedure was carried out with a biphasic solvent system composed of hexane-ethyl acetate-methyl alcohol-water (1:6:1:6, v/v) with triethylamine (10 mM) added to the upper organic phase as a retainer and hydrochloric acid (5 mM) to the aqueous mobile phase eluent. Two structurally similar compounds--nuciferine and roemerine--were also obtained from the crude lotus leaves extract. In total 500 mg of crude extract furnished 7.4 mg of N-demethylarmepavine, 45.3 mg of nuciferine and 26.6 mg of roemerine with purities of 90%, 92% and 96%, respectively. Their structures were further identified by HPLC/ESI-MSn, FTICR/MS and the comparison with reference compounds.

Numerical Simulations of the Soil-Rock Mixture Mechanical Properties Considering the Influence of Rock Block Proportions by PFC2D.

Soil-rock mixtures (S-RMs), as a kind of special engineering geological material, need to be studied because of the special structure and complex movement mechanism of their rock blocks, their physical and mechanical properties, and the factors underlying rock block movement in the process of their deformation and failure. In this paper, a series of discrete-element numerical models are constructed in particle flow code software (PFC2D). First, the random structure numerical models of S-RMs with different rock block proportions are established. Then, the parameters of the soil meso-structure are inversed by the biaxial simulation test, and a series of biaxial compressive tests are performed. The characteristics of stress and strain, deformation and failure, and rock block rotation and energy evolution are systematically investigated. The results show the following. (1) As the rock block proportion (confining pressure 0.5 MPa) increases, the peak strength of increases, the fluctuations of the post-peak become more obvious, and the dilatancy of the sample increases. (2) As the rock block proportion increases, the width of the shear band increases, the distribution of cracks becomes more complex and dispersed, and the range of the shear zone increases. (3) The number of rock blocks with rotation also increases significantly as rock block proportion increases, and the rotation angles are mostly between -5° and 5°. (4) The strain energy of S-RMs with different rock block proportions follows the same change rule as axial strain, showing a trend of first increasing and then decreasing, like the stress-strain curve.

Dexmedetomidine suppresses the development of abdominal aortic aneurysm by downregulating the mircoRNA­21/PDCD 4 axis.

Abdominal aortic aneurysm (AAA) is a pathological state with permanent dilation, which indicates a fatal potential for aortic rupture. It has been reported that dexmedetomidine (Dex) and microRNA (miR)­21 are involved in the progression of AAA. Thus, the present study aimed to investigate the joint effects of these factors on AAA treatment. For this purpose, rat models of AAA were established with enzyme perfusion and the rats were then injected with Dex. Alterations in the abdominal aorta in rats with AAA were recorded. miR­21 expression in the rats with AAA was determined. Inflammatory factor expression was detected by western blot analysis. Subsequently, a dual­luciferase reporter gene assay was performed to verify the targeting association between miR­21 and programmed cell death protein 4 (PDCD4). Additionally, AAA­related indices and inflammatory responses were examined by an injection of a combination of antagomiR (ant)­miR­21 and Dex or lentivirus­PDCD4­short hairpin RNA. It was found that Dex markedly alleviated the development of AAA and downregulated the expression of inflammatory factors and matrix metalloproteinase in rats with AAA. The high expression of miR­21, which targets PDCD4, was observed in the rats with AAA. However, ant­miR­21 induced AAA development and inflammatory responses. Additionally, the inhibition of PDCD4 reduced AAA development and inflammatory responses. On the whole, the present study demonstrates that Dex inhibits AAA development by downregulating the miR­21/PCDP4 axis. The findings of the present study may provide novel insight for the treatment of AAA. These findings may provide a reference for the future treatment of AAA and may provide theoretical guidance for the early prevention and development of AAA.

Integrated countercurrent extraction of natural products: a combination of liquid and solid supports.

An integrated online column-switching countercurrent chromatography (CCC) with a solid-phase trapping/preconcentration interface is presented. The interface is systematically evaluated in terms of sorbent type, column size, and kinetic factor from the view of the unique CCC process. Results indicate that satisfactory trapping efficiency can be achieved using a 25 mm x 10 mm i.d. column packed with Oasis HLB materials. In addition to the analyte focusing effect, large volume injection is avoided, thereby allowing the use of totally different biphasic liquid systems to enhance the system orthogonality. The present integrated system simply combines the liquid and solid supports and is successfully applied in a one-step preparative separation of four antioxidative compounds from the ethyl acetate extract of traditional Chinese herbal medicine Rubia cordifolia L. (Rubiaceae), exhibiting great advantages in peak resolution, peak capacity, and instrument integration compared with conventional CCC separations.

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 approximately 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.

Preparative separation of anti-oxidative constituents from Rubia cordifolia by column-switching counter-current chromatography.

An effective column-switching counter-current chromatography (CCC) protocol combining stepwise elution mode was successfully developed for simultaneous and preparative separation of anti-oxidative components from ethyl acetate extract of traditional Chinese herbal medicine Rubia cordifolia. The column-switching CCC system was interfaced by a commercial low-pressure six-port switching valve equipped with a sample loop, allowing large volume introduction from the first dimension (1st-D) to the second dimension (2nd-D). Moreover, to extend the polarity window, three biphasic liquid systems composed of n-hexane/ethyl acetate/methanol/water (1:2:1:2, 2:3:2:3, 5:6:5:6 v/v) were employed using stepwise elution mode in the 1st-D. By valve switching technique the whole interested region of 1st-D could be introduced to second dimension for further separation with the solvent system 5:5:4:6 v/v. Using the present column-switching CCC protocol, 500 mg of crude R. cordifolia extract were separated, producing milligram-amounts of four anti-oxidative components over 90% pure. Structures of purified compounds were identified by (1)H and (13)C NMR.

Screening of complex natural extracts by countercurrent chromatography using a parallel protocol.

In countercurrent chromatography (CCC) the choice of the liquid system is the heart of any separation. It corresponds to the selection of the mobile phase and the stationary phase at the same time. Any change in one phase composition induces a change in the other phase composition which renders the choice of the appropriate liquid system difficult and lengthy. A scale of compositions of the heptane-ethyl acetate-methanol-water quaternary liquid system was referred to by letters from A to Z and called the Arizona (AZ) liquid system. Each composition of the AZ system has the same heptane/ethyl acetate and methanol/water volume ratios. It is shown that there is a continuous polarity change from the hydrophilic A composition (ethyl acetate-water) to the hydrophobic Z (heptane-methanol) mixture by measuring the distribution constant K(D) of a known test mixture. For all compounds, the log K(D) is linearly increasing with the water content of the lower aqueous phase of the composition used. The slopes of the log K(D) versus percent H(2)O have very different values which means that the chromatographic selectivity changes with liquid system compositions. The AZ system was associated to the elution-extrusion method to design a procedure to identify rapidly the appropriate solvent composition able to fractionate correctly a complex natural extract. With the use of an integrated three-coil CCC column (40 mL each coil) able to test three AZ compositions in parallel, it is shown that the optimum AZ composition is found in half a day using less than a liter total volume of solvents. Two natural extracts are rapidly screened using the proposed protocol. An extract of Piper longum L. of intermediate polarity was fractionated in five usable portions using the 3/2/3/2 (Q) composition of the AZ system. A polar extract of Polygonum cuspidatum was also separated in five fractions using the 1/6/1/6 (D) composition. In both cases, a 140 mL CCC column was used for a direct scale-up transfer with the same liquid system. Purified fractions were subjected to an antioxidant activity assay and liquid chromatography with UV and mass spectrometry detection (LC-UV/MS) analysis to determine the molecular weight, number, and quantity of compounds in the active fractions. Four fractions of P. cuspidatum showed excellent antioxidant activity. They were rapidly produced at the milligram level by the 140 mL CCC column and fractionated by semipreparative high-performance liquid chromatography (HPLC) in individual compounds that were each identified by NMR and MS and reevaluated for confirmation of bioactivity. The rapid screening CCC protocol associated to the preparative capability of CCC allows for a fast identification and characterization of active compounds in natural products.