Xiaofang Hou

A vascular smooth muscle/cell membrane chromatography–offline-gas chromatography/mass spectrometry method for recognition, separation and identification of active components from traditional Chinese medicines

We describe an analytical method of vascular smooth muscle cell membrane chromatography (VSM/CMC) combined with gas chromatography/mass spectrometry (GC/MS) for recognition, separation and identification of active components from traditional Chinese medicines (TCMs). VSM cells by means of primary culture with rat thoracic aortas were used for preparation of the stationary phase in the CMC model. Retention components by the VSM-CMC model were collected and then analyzed by GC/MS under the optimized conditions in offline conditions. After investigating the suitability and reliability of the VSM/CMC-offline-GC/MS method using nifedipine and nitrendipine as standard compounds, this method was applied in screening active components from the extracts of TCMs such as Radix Angelicae Dahuricae (RAD), Rhizomza Seu Radix Notopterygii (RSRN), Radix Glehniae (RG) and Fructus Cnidii (FC). Retention components from the extracts in the VSM-CMC model were imperatorin and osthole identified by the GC/MS method. In vitro pharmacological trials indicated that imperatorin and osthole could concentration dependently relax the rat thoracic artery pre-contracted by KCl (P<0.05). The maximum relaxation effects (R(max)) were 63+/-5% and 40+/-6% for imperatorin and osthole, respectively. The VSM/CMC-offline-GC/MS method is an effective screening system that can rapidly detect and enrich target components from a complex sample and then accurately identify them.

Applications of HPLC/MS in the analysis of traditional Chinese medicines

In China, traditional Chinese medicines (TCMs) have been used in clinical applications for thousands of years. The successful hyphenation of high-Performance liquid chromatography (HPLC) and mass spectrometry (MS) has been applied widely in TCMs and biological samples analysis. Undoubtedly, HPLC/MS technique has facilitated the understanding of the treatment mechanism of TCMs. We reviewed more than 350 published papers within the last 5 years on HPLC/MS in the analysis of TCMs. The present review focused on the applications of HPLC/MS in the component analysis, metabolites analysis, and pharmacokinetics of TCMs etc. 50% of the literature is related to the component analysis of TCMs, which show that this field is the most populär type of research. In the metabolites analysis, HPLC coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry has been demonstrated to be the powerful tool for the characterization of structural features and fragmentation behavior patterns. This paper presented a brief overview of the applications of HPLC/MS in the analysis of TCMs. HPLC/MS in the fingerprint analysis is reviewed elsewhere.

Recent advances in cell membrane chromatography for traditional Chinese medicines analysis.

Traditional Chinese medicines (TCMs) have been used for preventative care for thousands of years. The active components are the basis for the pharmacodynamics of TCMs, and they can be an important source of lead compounds. As a bioaffinity chromatography technique, cell membrane chromatography (CMC) has been developed for almost 20 years since 1996. It has been proven to be a useful method for studying drug-receptor interactions and screening active components from medicinal herbs. In our review in 2007 (Drug Discov. Ther., 1 (2007) 104-107), the preparation, identification, evaluation, and preliminary applications of CMC stationary phases were presented. In this article, we briefly review some of the latest progress and applications about CMC including instrument development, research on drug-receptor interactions, screening active components from TCMs, and quality control of TCMs.

Screening active anti‐breast cancer compounds from Cortex Magnolia officinalis by 2D LC–MS

Most of the anti-breast cancer drugs are often limited owing to drug resistance and serious adverse reactions. Therefore, development of more targeted and low toxic drugs from traditional Chinese medicines for breast cancer are needed. At the same time, establishment of fast and effective drug screening methods are urgently required. We describe here a 2D LC method of MDA-MB-231 cell membrane chromatography combined with HPLC/MS for recognition, separation, and identification of target components from traditional Chinese medicine Cortex Magnolia officinalis. The MDA-MB-231 cells membrane was used to prepare the chromatographic stationary phase in the first dimension. The active compounds had a retention characteristic on the cell membrane chromatography model (10 × 2.0 mm, 5 μm). The retention fractions were enriched using an online C(18) column (10 × 1.0 mm, 5 μm) and were analyzed by the second dimension RP chromatography. Finally, the activity of the retention fractions was tested through in vitro experiments. Results showed that the retention fractions were honokiol and magnolol and the inhibition rate on MDA-MB-231 cell growth were 23 and 64 μM, respectively. These results support the conclusion that this coupled analytical technique could be an efficient method in drug discovery.

Determination of flavor enhancers in milk powder by one-step sample preparation and two-dimensional liquid chromatography.

Maltol, ethyl maltol, vanillin, and ethyl vanillin are important food additives as flavor enhancers. To quantify the four additives in milk powder, a novel 2D liquid chromatographic (2DLC) method was developed in this article. In such a 2DLC system, the target fractions eluted from the first dimensional column (C4) are stored onto the trapping column (C8) for subsequent analysis; after that, they were switched into the second dimensional column (C18) by a two-position six-port switching valve. A one-step sample preparation method was used prior to 2DLC chromatographic analysis, which was easy and convenient. After optimization of all experimental parameters, the new method was validated in terms of linearity, LODs, and LOQs, intra- and interday precision, and accuracy. A conventional single-dimensional liquid chromatographic method was also proposed in this work for comparison. In order to evaluate the applicability of the new 2DLC method, five brands of commercial milk powder samples (n = 8) were analyzed. Vanillin and ethyl vanillin were detected in two samples, respectively. It is showed that the 2DLC method is effective in quality control programs of milk powder products.

Photoexcited state properties of carbon dots from thermally induced functionalization of carbon nanoparticles

Carbon dots are small carbon nanoparticles with various surface passivation schemes, in which more effective has been the deliberate chemical functionalization of the nanoparticles for brighter fluorescence emissions, though the synthesis method is more tedious and subject to some limitations in the selection of functionalization molecules. Another more popular synthesis method has been the carbonization of organic species, with the method being more efficient and versatile, but less controllable in the synthesis and for the desired dot structure and performance. In this work, a hybrid approach combining the advantageous characteristics of the two synthesis methods was applied to the preparation of carbon dots with polyethyleneimine (PEI) for surface passivation, where pre-processed and selected small carbon nanoparticles were functionalized with PEI in microwave-induced thermal reactions. The optical absorption and fluorescence emission properties were evaluated, and the results suggested that the carbon dots thus prepared shared the same photoexcited state characteristics with those from the deliberate chemical functionalization, including comparable fluorescence colors and other properties. A further demonstration on the similarity in photoexcited state properties was based on the same visible light-activated bactericidal functions of the PEI-carbon dots as those found in carbon dots from the deliberate chemical functionalization. The advantages and potential limitations of the hybrid approach for more controllable yet versatile and efficient syntheses of carbon dots are highlighted and discussed.

An improved cell membrane chromatography method for the simultaneous screening of two epidermal growth factor receptor antagonists from radix scutellariae

A high-expression epidermal growth factor receptor cell membrane chromatography using the silica gel with the average particle size of 3 μm as the stationary phase carrier coupled with high-performance liquid chromatography and mass spectrometry was established for the online screening of epidermal growth factor receptor antagonists from Radix Scutellariae (Huang Qin in Chinese), a traditional Chinese medicine. In this study, the growth factor receptor cell membrane chromatography model using the smaller particle size carrier showed a higher efficiency for simultaneous screening baicalein, another one of the potential epidermal growth factor receptor antagonists from Radix Scutellariae extract besides wogonin, which was found in our previous work. The molecular docking result showed the occupancy site and binding mode of baicalein and wogonin with epidermal growth factor receptor tyrosine kinase were similar to gefitinib. The result of the assay for the in vitro inhibitory activity showed that baicalein and wogonin inhibited the growth of the high-expression epidermal growth factor receptor cell in a dose-dependent manner and even achieved a better inhibition effect than gifitinib in the low-dosage range.

An online coupled breast cancer cell membrane chromatography with HPLC/MS for screening active compounds from Fructus evodiae

As a preliminary stage of drug discovery, the screening of active compounds from complex systems requires efficient and accurate techniques. In our study, a two dimensional liquid chromatography method was developed for the fast screening of anti-breast cancer compounds. MDA-MB-231 cell membrane chromatography and high performance liquid chromatography/mass spectroscopy was combined online for recognition, separation, and identification of target components from the traditional Chinese medicine Fructus evodiae. Here, the breast cancer cells MDA-MB-231 were used to prepare the chromatographic stationary phase in the first dimension. The target compounds had a retention characteristic on cell membrane chromatography. The retention fraction was enriched using an online C18 column and was analyzed by the second dimensional reversed phase chromatography. Finally, the activity of the retention fractions was tested through in vitro experiments. Results showed that the target compounds were evodiamine and rutaecarpine and their IC50 values were 33.4 μM and 73.4 μM, respectively, which illustrated that they could inhibit the growth of MDA-MB-231 cells. These results support the conclusion that this coupled analytical technique could be an efficient method in drug discovery.

Modified facile synthesis for quantitatively fluorescent carbon dots

A simple yet consequential modification was made to the popular carbonization processing of citric acid - polyethylenimine precursor mixtures to produce carbon dots (CDots). The modification was primarily on pushing the carbonization processing a little harder at a higher temperature, such as the hydrothermal processing condition of around 330 °C for 6 hours. The CDots thus produced are comparable in spectroscopic and other properties to those obtained in other more controlled syntheses including the deliberate chemical functionalization of preprocessed and selected small carbon nanoparticles, demonstrating the consistency in CDots and reaffirming their general definition as carbon nanoparticles with surface passivation by organic or other species. Equally significant is the finding that the modified processing of citric acid - polyethylenimine precursor mixtures could yield CDots of record-setting fluorescence performance, approaching the upper limit of being quantitatively fluorescent. Thus, the reported work serves as a demonstration on not only the need in selecting the right processing conditions and its associated opportunities in one-pot syntheses of CDots, but also the feasibility in pursuing the preparation of quantitatively fluorescent CDots, which represents an important milestone in the development and understanding of these fluorescent carbon nanomaterials.

A stop-flow two-dimensional liquid chromatography method for determination of food additives in yogurt

A heart-cutting, two-dimensional (2D) high performance liquid chromatography method was developed in this research to simultaneously quantify five food additives (aspartame, benzoic acid, natamycin, saccharin sodium and sorbic acid) in yogurt drinks. In this 2D system, a Venusil XBP-C4 column was selected in the first dimension as a pre-separation column; a Purospher® STAR RP-18 column was employed in the second dimension as a further analysis column; a two position, six-port switching valve was used to transfer the targets from the first dimension to the second dimension under stop-flow conditions. To investigate the specificity and accuracy of the new system, it was validated in terms of selectivity, response function, linearity, precision, sensitivity and recovery. In addition, a conventional single-dimensional high performance liquid chromatography method was also proposed for comparison. The recovery of food additives obtained with the new method (from 94.5% to 103.9%) was significantly better than that obtained with the conventional method (from 75.1% to 110.4%). Furthermore, this new method benefits from a simplified one-step sample preparation procedure, which contributes to a shorter analysis time, more accurate results and less solvent usage.