Efficient One-Step Separation of Five Flavonoids from the Crude Extract of the Waste Pomace of Sea Buckthorn Berries through Counter-Current Chromatography

The pomace of sea buckthorn berries is usually discarded when transforming into nonalcoholic or alcoholic beverages, jellies, jams, juices, candies and dairy products. Here, we established a promising approach for one step separation of five flavonoids from the waste pomace of sea buckthorn berries through counter-current chromatography. The crude extract of waste pomace of sea buckthorn berries after juicing was injected into counter-current chromatography with hexane/ethyl acetate/ethanol/water (v/v/v/v, 5:7:5:7) as the solvent system. As a result, five flavonoids, including quercetin, laricitrin, isorhamnetin-7-O-rhamnoside, kaempferol and isorhamnetin, were obtained in a single step separation. Our finding showed that ethanol is a good substitute for methanol to regulate the partition coefficient in hexane/ethyl acetate/ methanol/water system. This study provided a significant measure to utilize the waste pomace of Sea buckthorn berries.

HSCCC Separation of Three Main Compounds from the Crude Extract of Dracocephalum Tanguticum by Using Dimethyl Sulfoxide as Cosolvent

Separation of natural compounds directly from the crude extract is a challenging work for traditional column chromatography. In the present study, an efficient method for separation of three main compounds from the crude extract of Dracocephalum tanguticum has been successfully established by high-speed counter-current chromatography (HSCCC). The crude extract was directly introduced into HSCCC by using dimethyl sulfoxide as cosolvent. Ethyl acetate/n-butyl alcohol/0.3% glacial acetic acid (4: 1: 5, v/v) system was used and three target compounds with purity higher than 80% were obtained. Preparative HPLC was used for further purification and three target compounds with purity higher than 98% were obtained. The compounds were identified as chlorogenic acid, pedaliin and pedaliin-6″-acetate.

Extraction process and method validation for bioactive compounds from Citrus reticulata cv. Chachiensis: Application of response surface methodology and HPLC–DAD

Citrus reticulata cv. Chachiensis, a traditional Chinese herb, has extensive medicinal and edible effects. 3′,4′,5,6,7,8-Hexamethoxyflavone (HM) and 5,6,7,8,4′-pentamethoxyflavone (PM) are main bioactive compounds in Chachiensis, which have been reported to possess various biological properties. In this study, supercritical CO2 extraction (SCE) and high-speed countercurrent chromatography (HSCCC) were utilized to prepare HM and PM from Chachiensis. The contents of target compounds were determined by a high-performance liquid chromatography method with diode-array detection (HPLC-DAD), which was validated using the following parameters: linearity, sensitivity, repeatability, stability, precision and accuracy. The SCE conditions were optimized using response surface methodology with central composite design. Obtained optimum conditions were temperature of 37.9 °C, pressure of 26.3 MPa, and modifier volume of 81.0 mL. Under above conditions, the recoveries of target compounds were 92.52 ± 0.83 and 96.36 ± 0.43%, respectively. The most appropriate solvent system for HSCCC was selected as n-hexane/ethyl acetate/methanol/water (1:0.8:1:1.2, v/v). The HSCCC fractions were detected by HPLC-DAD, liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance spectroscopy (1H NMR and 13C NMR). The results indicated that this method was successfully applied to obtain HM and PM with high purities and high recoveries from Chachiensis.

Diagnostic ion filtering targeted screening and isolation of anti-inflammatory iridoid glycosides from Hedyotis diffusa

Efficient and targeted screening and isolation of bioactive compounds from complex natural products is still a challenging work. Herein, diagnostic ion filtering based high-performance liquid chromatography-quadrupole time-of-flight-tandem mass spectrometry was firstly developed to screen six main iridoid glycosides from Hedyotis diffusa. Then, online extraction-high-speed counter current chromatography was proposed for targeted enrichment and preparative isolation using ethyl acetate/n-butanol/water (4.5:0.5:5, v/v/v) as solvent system. After that, Sephadex LH-20 column chromatography using methanol as solvent system was selected for further purification of six iridoid glycosides with purities over 98%. They were finally identified as monotropein, desacetylasperuloside acid, asperuloside, 6-O-(Z)-p-coumaroyl scandoside methyl ester, 6-O-(Z)-feruloyl scandoside methyl ester, and 6-O-(E)-p-coumaroyl scandoside methyl ester. And their anti-inflammatory activities were evaluated and confirmed by lipopolysaccharide activated RAW 264.7 macrophages. Obviously, the results provide a scientific basis for the potential applications of H. diffusa, and the developed methodology is efficient and reliable for targeted screening and isolation of bioactive compounds from natural products.

Recent progress in separation prediction of counter-current chromatography

As a liquid-liquid partition chromatography, counter-current chromatography has advantages in large sample loading capacity without irreversible adsorption, which has been widely applied in separation and purification fields. The main factors, including partition coefficient, two-phase solvent systems, apparatus, and operating parameters greatly affect the separation process of counter-current chromatography. To promote the applications of counter-current chromatography, it is essential to develop theoretical research to master the principles of counter-current chromatographic separations so as to achieve predictions before laborious trials. In this article, recent progress about separation prediction methods are reviewed from a point of the steady and unsteady state of the mass transfer process of counter-current chromatography and its mass transfer characteristics, and then it is divided into three aspects: prediction of partition coefficient, modeling the thermodynamic process of counter-current chromatography, and modeling the dynamic process of counter-current chromatography.

Comparison of microwave-assisted and conventional extraction of mangiferin from mango (Mangifera indica L.) leaves

Mangiferin is the main bioactive component in mango leaves, which possesses anti-inflammatory, antioxidative, antidiabetic, immunomodulatory, and antitumor activities. In the present study, a microwave-assisted extraction method was developed for the extraction of mangiferin from mango leaves. Some parameters such as ethanol concentration, liquid-to-solid ratio, microwave power, and extraction time were optimized by single-factor experiments and response surface methodology. The optimal extraction conditions were 45% ethanol, liquid-to-solid ratio of 30:1 (mL/g), and extraction time of 123 s under microwave irradiation of 474 W. Under optimal conditions, the yield of mangiferin was 36.10 ± 0.72 mg/g, significantly higher than that of conventional extraction. The results obtained are beneficial for the full utilization of mango leaves and also indicate that microwave-assisted extraction is a very useful method for extracting mangiferin from plant materials.