Preparative separation of rhein from Chinese traditional herb by repeated high-speed counter-current chromatography

Luteolin-7-O-rutinoside Protects RIN-5F Cells from High-Glucose-Induced Toxicity, Improves Glucose Homeostasis in L6 Myotubes, and Prevents Onset of Type 2 Diabetes

Luteolin-7-O-rutinoside (lut-7-O-rutin), a flavonoid commonly present in Mentha longifolia L. and Olea europaea L. leaves has been used as a flavoring agent with some biological activity. The present study is the first attempt to analyze the protective effect of lut-7-O-rutin on high-glucose-induced toxicity to RIN-5F cells in vitro. We found that lut-7-O-rutin improved insulin secretion in both normal and high-glucose conditions in a dose-dependent manner, without toxicity observed. In addition, 20 µmol of lut-7-O-rutin improves insulin sensitization and glucose uptake significantly (p ≤ 0.01) in L6 myotubes cultured in a high-glucose medium. Lut-7-O-rutin has shown a significant (p ≤ 0.05) effect on glucose uptake in L6 myotubes compared to the reference drug, rosiglitazone (20 µmol). Gene expression analysis confirmed significantly lowered CYP1A, TNF-α, and NF-κb expressions in RIN-5F cells, and increased mitochondrial thermogenesis-related LPL, Ucp-1 and PPARγC1A mRNA expressions in L6 myotubes after 24 h of lut-7-O-rutin treatment. The levels of signaling proteins associated with intracellular glucose uptakes, such as cAMP, ChREBP-1, and AMPK, were significantly increased in L6 myotubes. In addition, the levels of the conversion rate of glucose to lactate and fatty acids were raised in insulin-stimulated conditions; the rate of glycerol conversion was found to be higher at the basal level in L6 myotubes. In conclusion, lut-7-O-rutin protects RIN-5F cells from high-glucose-induced toxicity, stimulates insulin secretion, and promotes glucose absorption and homeostasis via molecular mechanisms.

Therapeutic Emergence of Rhein as a Potential Anticancer Drug: A Review of Its Molecular Targets and Anticancer Properties

According to the World Health Organization (WHO), cancer is the second-highest cause of mortality in the world, and it kills nearly 9.6 million people annually. Besides the fatality of the disease, poor prognosis, cost of conventional therapies, and associated side-effects add more burden to patients, post-diagnosis. Therefore, the search for alternatives for the treatment of cancer that are safe, multi-targeted, effective, and cost-effective has compelled us to go back to ancient systems of medicine. Natural herbs and plant formulations are laden with a variety of phytochemicals. One such compound is rhein, which is an anthraquinone derived from the roots of Rheum spp. and Polygonum multiflorum. In ethnomedicine, these plants are used for the treatment of inflammation, osteoarthritis, diabetes, and bacterial and helminthic infections. Increasing evidence suggests that this compound can suppress breast cancer, cervical cancer, colon cancer, lung cancer, ovarian cancer, etc. in both in vitro and in vivo settings. Recent studies have reported that this compound modulates different signaling cascades in cancer cells and can prevent angiogenesis and progression of different types of cancers. The present review highlights the cancer-preventing and therapeutic properties of rhein based on the available literature, which will help to extend further research to establish the chemoprotective and therapeutic roles of rhein compared to other conventional drugs. Future pharmacokinetic and toxicological studies could support this compound as an effective anticancer agent.

Chromatographic Characterization and GC-MS Evaluation of the Bioactive Constituents with Antimicrobial Potential from the Pigmented Ink of Loligo duvauceli

Chromatographic characterization and the GC-MS evaluation of the black pigmented ink of Loligo duvauceli in the present study have yielded an array of bioactive compounds with potent antimicrobial property. Facing an alarm of antimicrobial resistance globally, a need for elucidating antimicrobial agents from natural sources will be the need for the hour. In this view, this study is aimed at characterizing the black pigmented ink of the Indian squid L. duvauceli. The squid ink was subjected to crude solvent extraction and was fractionated by silica gel column chromatography. TLC and HPTLC profiles were recorded. Antimicrobial bioassay of the squid ink fractions was done by agar well diffusion method. The antimicrobial fraction was then characterized using GC-MS analysis. The results showed that the n-hexane extract upon column fractionation yielded a total of 8 fractions with the mobile phase of Hex/EtOAc in different gradients. TLC and HPTLC profiles showed a single spot with a retention factor of 0.76. Fraction 1 showed significant antibacterial activity against Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, and Lactobacillus acidophilus and a promising antifungal activity against Candida albicans. The antimicrobial fraction upon GC-MS analysis of bis(2-ethylhexyl) phthalate (BEHP) possesses the highest percentage of area normalisation (91%) with other few minor constituents. The study is concluded by stating that the antimicrobial efficacy of the squid ink might be due to the synergistic effects of the phthalate derivative and the other minor volatile compounds analysed in the squid ink.

Antifeedant and larvicidal activities of Rhein isolated from the flowers of Cassia fistula L

Antifeedant and larvicidal activities of rhein (1,8-dihydroxyanthraquinone-3-carboxylic acid) isolated from the ethyl acetate extract of Cassia fistula flower were studied against lepidopteron pests Spodoptera litura and Helicoverpa armigera. Significant antifeedant activity was observed against H. armigera (76.13%) at 1000 ppm concentration. Rhein exhibited larvicidal activity against H. armigera (67.5), S. litura (36.25%) and the LC50 values was 606.50 ppm for H. armigera and 1192.55 ppm for S. litura. The survived larvae produced malformed adults.

Comparison of three different extraction methods and HPLC determination of the anthraquinones aloe-emodine, emodine, rheine, chrysophanol and physcione in the bark of Rhamnus alpinus L. (Rhamnaceae)

INTRODUCTION

Rhamnus alpinus L. (Rhamnaceae), a traditional plants in the flora of the Abruzzo region, is known to contain active anthraquinone secondary metabolites. However, the content of anthraquinones varies among R. alpinus samples depending on collection season and site. Thus, using simple, reliable and accurate analytical methods for the determination of anthraquinones in R. alpinus extracts allows comparative study of different methods of extraction.

OBJECTIVE

After a partial validation of an HPLC method for the simultaneous determination of five anthraquinones, aloe-emodine, rheine, emodine, chrysophanol and physcione, in the bark of R. alpinus, we compared three different methods of extraction.

METHODOLOGY

Anthraquinones were extracted from the bark of R. alpinus using different techniques (methanol maceration, ultrasonic and supercritical CO(2) extraction). Separation and quantification of anthraquinones were accomplished using a reversed-phase C(18) column with the mobile phase of H(2)O-methanol (40 : 60, v/v, 1% formic acid) at a wavelength of 254 nm. The qualitative analyses were also achieved at wavelength of 435 nm.

RESULTS

All calibration curves were linear over the concentration range tested (10-200 mM) with the determination coefficients >or=0.991. The detection limits (S/N = 3) were 5 mM for each analytes. All five anthraquinones were found in the samples tested at concentrations reported in experimental data.

CONCLUSION

The described HPLC method and optimised extraction procedure are simple, accurate and selective for separation and quantification of anthraquinones in the bark of R. alpinus and allow evaluation of the best extraction procedure between the tested assays.

Simultaneous determination of five anthraquinones in medicinal plants and pharmaceutical preparations by HPLC with fluorescence detection

A reversed-phase high-performance liquid chromatography (RP-HPLC) method with fluorescence detection for simultaneous determination of five anthraquinones in Rhubarb collected from nine different locations in China, Polygonum cuspidatum, Polygoni multiflori and three pharmaceutical preparations is proposed and validated. Chromatography was carried out at 25 degrees C on a Hypersil C18 column with the isocratic mobile phase of methanol-0.1% aqueous formic acid (85:15, v/v) at a flow rate of 1.0 ml/min. The excitation and emission wavelengths were set at 440 and 540 nm, respectively. A comprehensive validation of the method included tests of sensitivity, linearity, precision and accuracy. The linear regressions were acquired with r>0.999. Satisfactory intra- and inter-day precisions were achieved with R.S.D.s less than 3.95% and the average recovery factors obtained were in the range of 93.2-103.8%.

Inhibition of cytochrome P450 enzymes by rhein in rat liver microsomes

Rhein, an active ingredient extensively found in plants such as Aloe, Cassitora L., rhubarb and so on, has been used for a long time in China. Pharmacological tests revealed that rhein not only had a strong antibacterial action, but also may be useful in cancer chemotherapy as a biochemical modulator. Its therapeutic action and toxicity is still the subject of considerable research. With microsome incubation assays in vitro and HPLC methods, the inhibition of rat liver CYP1A2, CYP2C9, CYP2D6, CYP2E1 and CYP3A enzymes by rhein were studied kinetically. The results showed the most inhibition of CYP2E1 by rhein (K(i) = 10 microm, mixed); CYP3A and CYP2C9 were also inhibited by rhein, K(i) = 30 microm (mixed) and K(i) = 38 microm (mixed), respectively; rhein revealed some inhibition of CYP1A2 (K(i) = 62 microm, uncompetitive) and CYP2D6 (K(i) = 74 microm, mixed). Drug-drug interactions, especially cytochrome P450 (CYP)-mediated interactions, cause an enhancement or attenuation in the efficacy of co-administered drugs. Inhibition of the five major CYP enzymes observed for rhein suggested that changes in pharmacokinetics of co-administered drugs were likely to occur. Therefore, caution should be paid to the possible drug interaction of medicinal plants containing rhein and CYP substrates.

Countercurrent chromatography: people and applications

The scientific literature was scanned for the published research articles dealing with countercurrent chromatography (CCC) over the time period 1980-May 2008. The search returned 1638 articles that were analyzed focussing on people and applications. Concerning the people, it was found that the geographical location of the CCC authors was relatively well balanced between USA, Asia with mainly China and Japan and Europe. Yoichiro Ito, the inventor of the technique, is by far the most productive author in the field with 331 articles or more than one over five CCC articles published in the time period. Without surprise, English is the dominant language with more than 82% of the articles. A significant 8% amount of CCC articles were published in Chinese in Chinese journals. Chromatography journals are the logical tribune for half of the published CCC articles. Concerning the applications, the separation and purification of natural compounds is the dominant theme in CCC making the subject of more than one article over two. Starting from the plant extract, CCC in few steps can produce significant amounts of more than 95% pure compounds used for identification and/or property studies. Other applications are found in the pharmaceutical and chemical field. The separation of enantiomers on the preparative scale is a field of growing importance.

Traditional Chinese medicine and separation science

Traditional Chinese medicines (TCMs) are getting more and more popular nowadays in the whole world for improving health condition of human beings as well as preventing and healing diseases. TCM is a multi-component system with components mostly unknown, and only a few compounds are responsible for the pharmaceutical and/or toxic effects. The large numbers of other components in the TCM make the screening and analysis of the bioactive components extremely difficult. So, separation and analysis of the desired chemical components in TCM are very important subjects for modernization research of TCM. Thus, many novel separation techniques with significant advantages over conventional methods were introduced and applied to separation and analysis of the chemical constituents in TCM. This review presents just a brief outline of the applications of different separation methods for the isolation and analysis of TCM constituents.

Qualitative and quantitative analysis in quality control of traditional Chinese medicines

Separation techniques with high efficiency and sensitive detection have been widely used for quality control of traditional Chinese medicines (TCMs). High-performance liquid chromatography, gas chromatography, and capillary electrophoresis are commonly used to separate various components in TCMs. Ultraviolet detection, fluorescence detection, evaporative light-scattering detection, mass spectrometry and nuclear magnetic resonance can be applied to separation techniques for qualitative and quantitative analysis of TCMs. The development of quality control for TCMs based on quantitative and qualitative analysis from 2000 to 2007 are reviewed; the fingerprint technique is also discussed due to its broad application in the quality control of TCMs. Prospects for further research based on our primary results are also discussed.

Natural product isolation

Since the 1990s, interest in natural product research has increased considerably. Following several outstanding developments in the areas of separation methods, spectroscopic techniques, and sensitive bioassays, natural product research has gained new attention for providing novel chemical entities. This updated review deals with sample preparation and purification, recent extraction techniques used for natural product separation, liquid-solid and liquid-liquid isolation techniques, as well as multi-step chromatographic operations. It covers examples of papers published since the NPR review 'Modern separation methods' by Marston and Hostettmann,1 with major emphasis on methods developed and the research undertaken since 2000.

Preparative isolation and purification of flavone compounds fromSophora japonica L. by high-speed counter-current chromatography combined with macroporous resin column separation

High-speed counter-current chromatography combined with macroporous resin column separation was applied to the isolation and purification of genistein-7,4'-di-O-beta-D-glucoside (I), genistein-7-O-beta-D-glucopyranoside-4'-O-[(alpha-L-rhamnopyransoyl)-(1-2)-beta-D-glucopyranoside] (II), kaempferol-3-O-beta-D-sophoroside(III), quercetin-3-O-beta-L-ramnopyranosyl-(1 - 6)-beta-D-glucopyranoside (IV), genistein-4'-beta-L-rhamnopyransoyl-(1 - 2)-alpha-D-glucopyranoside (V), and kaempferol-3-O-beta-L-ramnopyranosyl-(1 - 6)-beta-D-glucopyranoside (VI) from the Chinese medicinal herb Sophora japonica L. The crude extracts from the pericarps of Sophora japonica L. were pre-separated on a D-101 macroporous resin column and divided into two parts as sample 1 and sample 2. An 80-mg portion of sample 1 was separated by using n-butanol-acetic acid (1%) (5:5, v/v) as the two-phase solvent system and yielded 30.1 mg of compound I, 23.3 mg of compound II. A 120 mg portion of sample 2 was separated by using ethyl acetate-n-butanol-acetic acid (1%) (5:0.8:5, v/v) as the two-phase solvent system and yielded 5.5 mg of compound III, 31.7 mg of compound IV, 37.4 mg of compound V, and 6.2 mg of compound VI. The purities of compounds I, II, III, IV, V, and VI were 98.7, 98.2, 97.8, 98.5, 99.3, and 98.9%, respectively, as determined by HPLC. The chemical structures of these components were identified by 1H-NMR and 13C-NMR.

Supercritical CO2 extraction of emodin and physcion from Polygonum cuspidatum and subsequent isolation by semipreparative chromatography

Emodin and physcion are abundant anthraquinone compounds found in the traditional Chinese medicinal herb Polygonum cuspidatum Sied. et Zucc. In this paper, emodin and physcion were successfully extracted with supercritical CO2 plus ethanol modifier after the extraction conditions were optimized with uniform design-sequential optimization. Results showed that the ethanol modifier concentration was the main factor for the effective extraction of the emodin. The optimal extraction condition was obtained: 20 MPa, 30 degrees C, and 95% ethanol, at which the yields of emodin and physcion were 0.616 and 0.178 g/100 g, respectively. The yield obtained by supercritical fluid extraction (SFE) was a little lower than that obtained by sonication extraction (SE). The crude extract obtained by SFE was further isolated and purified by semipreparative chromatography with the mobile phase composed of methanol-water (90:1, v/v). Emodin and physcion were obtained with purity 98.6 and 99.1%, respectively, when determined by HPLC, and identification was performed by retention time and UV spectra of the standards. The result suggested that SFE is an alternative and promising method for extraction of the two compounds from P. cuspidatum owing to its environment-friendly properties and fewer coextracts.

Preparative isolation and purification of germacrone and curdione from the essential oil of the rhizomes of Curcuma wenyujin by high-speed counter-current chromatography

High-speed counter-current chromatography (HSCCC) was applied to isolate and purify bioactive compounds in the essential oil of the rhizomes of Curcuma wenyujin. Two sesquiterpenes germacrone and curdione were successfully isolated and purified using two-phase solvent system composed of petroleum ether-ethanol-diethyl ether-water (5/4/0.5/1, v/v) in tail to head elution mode. 62 mg of germacrone and 93 mg of curdione were obtained from 658 mg of the essential oil each at over 95% purity. Their structures were identified by 1H NMR and EI MS.

Application of preparative high-speed counter-current chromatography for separation of methyl gallate from Acer truncatum Bunge

Preparative separation of methyl gallate in leaves extract of Acer truncatum Bunge was conducted using high-speed counter-current chromatography (HSCCC) with a solvent system composed of ethyl acetate-ethanol-water at volume ratios of 5:1:5 (v/v/v). In a single operation, 57.5 mg of methyl gallate was obtained from 120 mg of the extract. HPLC analyses of the counter-current chromatography (CCC) fraction revealed that the methyl gallate was having over 97% purity. Its structure was identified by 1H NMR and 13C NMR.

Isolation and purification of coumarin compounds from Cortex fraxinus by high-speed counter-current chromatography

High-speed counter-current chromatography (HSCCC) was successfully used for the isolation and purification of coumarin compounds from Cortex fraxinus, the Chinese herbal drug. n-Butanol-methanol-0.5% acetic acid (5:1.5:5, v/v) was used as the two-phase solvent system. 14.3 mg of fraxin, 26.5 mg of aesculin, 5.8 mg of fraxetin and 32.4 mg of aesculetin with the purity of 97.6, 99.5, 97.2 and 98.7%, respectively were obtained from 150 mg of crude extracts of C. fraxinus in a single run. The structures of the isolated compounds were identified by 1H NMR and 13C NMR.

Isolation of quercetin-3-O-l-rhamnoside from Acer truncatum Bunge by high-speed counter-current chromatography

Preparative high-speed counter-current chromatography (HSCCC) was successfully used for isolation and purification of quercetin-3-O-L-rhamnoside from the ethyl acetate extract of the leaves of Acer truncatum Bunge using a two-phase-system composed of ethyl acetate-ethanol-water at a volume ratio of 5:1:5 (v/v/v). In a single operation, 41.9mg of quercetin-3-O-L-rhamnoside was obtained from 366mg of the crude extract. High-performance liquid chromatography (HPLC) analyses of the CCC fraction revealed that the purity of quercetin-3-O-L-rhamnoside was over 96%. Its structure was identified by MS, 1H NMR and 13C NMR. Quercetin-3-O-L-rhamnoside was obtained from this plant for the first time.

Recent advances in analysis of Chinese medical plants and traditional medicines

Chinese herbal medicine is gaining increasing popularity worldwide for health promotion and adjuvant therapy. Thus, selective and efficient analytical methods are required not only for quality assurance but also for authentication of the plant material. Applications of both chromatographic and electrophoretic techniques to the analysis of medicinal plants and Chinese traditional medicine preparations over the last 3 years are outlined in this review. The role of chemical fingerprinting is highlighted and a brief survey of determination of toxic components, natural and synthetic adulterants is also included. Moreover, different sample pretreatment and extraction methods are discussed.

Preparative isolation and purification of gastrodin from the Chinese medicinal plant Gastrodia elata by high-speed counter-current chromatography

Gastrodia elata Blume is a famous Chinese medicinal plant, which has been widely used for the treatment of rheumatism, epilepsy, paralysis, hemiplegia, lumbago, headache and vertigo. High-speed counter-current chromatography was successfully used for the first time for the preparative isolation and purification of the bioactive component gastrodin from G. elata Blume. The crude gastrodin was obtained by extraction with ethanol from the dried roots of G. elata Blume under sonication. Preparative high-speed counter-current chromatography with a two-phase solvent system composed of n-butanol-ethyl acetate-water (2:3:5, v/v/v) was successfully performed yielding 48 mg gastrodin at 96% purity from 500 mg of the crude extract (10.3% gastrodin) with the recovery of approximately 90% in a one-step separation.