One-step separation and purification of three lignans and one flavonol from Sinopodophyllum emodi by medium-pressure liquid chromatography and high-speed counter-current chromatography

Extraction Techniques and Analytical Methods for Isolation and Characterization of Lignans

Lignans are a group of natural polyphenols present in medicinal plants and in plants which are a part of the human diet for which more and more pharmacological activities, such as antimicrobial, anti-inflammatory, hypoglycemic, and cytoprotective, are being reported. However, it is their cytotoxic activities that are best understood and which have shed light on this group. Two anticancer drugs, etoposide, and teniposide, were derived from a potent cytotoxic agent—podophyllotoxin from the roots of Podophyllum peltatum. The evidence from clinical and observational studies suggests that human microbiota metabolites (enterolactone, enterodiol) of dietary lignans (secoisolariciresinol, pinoresinol, lariciresinol, matairesinol, syringaresinol, medioresinol, and sesamin) are associated with a reduced risk of some hormone-dependent cancers. The biological in vitro, pharmacological in vivo investigations, and clinical studies demand significant amounts of pure compounds, as well as the use of well-defined and standardized extracts. That is why proper extract preparation, optimization of lignan extraction, and identification are crucial steps in the development of lignan use in medicine. This review focuses on lignan extraction, purification, fractionation, separation, and isolation methods, as well as on chromatographic, spectrometric, and spectroscopic techniques for their qualitative and quantitative analysis.

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.

A combination strategy for extraction and isolation of multi-component natural products by systematic two-phase solvent extraction-(13)C nuclear magnetic resonance pattern recognition and following conical counter-current chromatography separation: Podophyllotoxins and flavonoids from Dysosma versipellis (Hance) as examples

Despite of substantial developments of extraction and separation techniques, isolation of natural products from natural resources is still a challenging task. In this work, an efficient strategy for extraction and isolation of multi-component natural products has been successfully developed by combination of systematic two-phase liquid-liquid extraction-(13)C NMR pattern recognition and following conical counter-current chromatography separation. A small-scale crude sample was first distributed into 9 systematic hexane-ethyl acetate-methanol-water (HEMWat) two-phase solvent systems for determination of the optimum extraction solvents and partition coefficients of the prominent components. Then, the optimized solvent systems were used in succession to enrich the hydrophilic and lipophilic components from the large-scale crude sample. At last, the enriched components samples were further purified by a new conical counter-current chromatography (CCC). Due to the use of (13)C NMR pattern recognition, the kinds and structures of major components in the solvent extracts could be predicted. Therefore, the method could collect simultaneously the partition coefficients and the structural information of components in the selected two-phase solvents. As an example, a cytotoxic extract of podophyllotoxins and flavonoids from Dysosma versipellis (Hance) was selected. After the systematic HEMWat system solvent extraction and (13)C NMR pattern recognition analyses, the crude extract of D. versipellis was first degreased by the upper phase of HEMWat system (9:1:9:1, v/v), and then distributed in the two phases of the system of HEMWat (2:8:2:8, v/v) to obtain the hydrophilic lower phase extract and lipophilic upper phase extract, respectively. These extracts were further separated by conical CCC with the HEMWat systems (1:9:1:9 and 4:6:4:6, v/v). As results, total 17 cytotoxic compounds were isolated and identified. In general, whole results suggested that the strategy was very efficient for the systematic extraction and isolation of biological active components from the complex biomaterials.

Preparative isolation of six anti-tumour biflavonoids from Selaginella doederleinii Hieron by high-speed counter-current chromatography

INTRODUCTION

Biflavonoids are the primary constituents of Selaginella doederleinii Hieron, to which different bioactivities have been attributed, including anti-cancer, anti-inflammatory, anti-oxidant, anti-fungal and anti-virus activity. However, effective methods for separation of these compounds are not currently available.

OBJECTIVE

To develop a high performance and bioassay-guided method for preparative isolation of biflavonoids from S. doederleini via high-speed counter-current chromatography (HSCCC).

METHODS

The anti-proliferation effects of four fractions (70% ethanol, petroleum ether, dichloromethane and acetic ether extracts) of S. doederleinii on five human cancer cells were monitored. The dichloromethane and acetic ether extracts showed good cytotoxicities to the studied cancer cell lines, guiding the subsequent separation. Two solvent systems composed of n-hexane:ethyl acetate:methanol:water (1:2:1.5:1.5, v/v) and n-hexane:ethyl acetate:methanol:water (3:2:3:2, v/v) were developed for separation of the active fractions, respectively. Identification of the biflavonoids was performed by EI-MS(n) , (1) H- and (13) C-NMR.'

RESULTS

Under the optimised conditions, 12.6 mg amentoflavone (91.4%), 6.6 mg robustaflavone (90.4%), 7.5 mg 2'', 3''-dihydro-3', 3'''-biapigenin (98.2%) and 7.3 mg 3', 3'''-binaringenin (90.3%) from acetic ether extract (500 mg) and 6.3 mg heveaflavone (93.5%) and 5.3 mg 7, 4', 7'', 4'''-tetra-O-methyl-amentoflavone (94.5%) from dichloromethane extract (200 mg) were obtained, respectively. The anti-proliferation effects of the six biflavonoids on the five human cancer cells were further verified.

CONCLUSION

The study provides methodological references for simultaneously preparative isolation of several bioactive biflavones from the herbal family of Selaginella. It is the first report discovering 2'', 3''-dihydro-3', 3'''-biapigenin and 3', 3'''-binaringenin from this herb and describing their cytotoxicities to human cancer cell lines.