Preparative separation of five polyphenols from the fruits of Sorbus pohuashanensis Hedl. by high-speed counter-current chromatography

Properties, extraction and purification technologies of Stevia rebaudiana steviol glycosides: A review

For health and safety reasons, the search for green, healthy, and low-calorie sweeteners with good taste has become the demand of many consumers. Furthermore, the need for sugar substitutes of natural origin has increased dramatically. In this review, we briefly discussed the safety and health benefits of stevia sweeteners and enumerated some examples of physiological functions of steviol glycosides (SGs), such as anti-inflammatory, anti-obesity, antihypertensive, anti-diabetes, and anticaries, citing various evidence related to their application in the food industry. The latest advances in emerging technologies for extracting and purifying SGs and the process variables and operational strategies were discussed. The impact of the extraction methods and their comparison against the conventional techniques have also been demonstrated. These technologies use minimal energy solvents and simplify subsequent purification stages, making viable alternatives suitable for a possible industrial application. Furthermore, we also elucidated the potential for advancing and applying the natural sweeteners SGs.

Optimisation of isolation of polyphenols from Malus pumila Mill. Leaves by high-speed countercurrent chromatography using response surface methodology

Considering comprehensive utilization of natural products, isolation and activity determination processes of bioactive compounds are essential. In this study, a combined high-speed countercurrent chromatography (HSCCC) with preparative HPLC method was developed to isolate the five antioxidant polyphenols from 75% ethanol extract of Malus pumila Mill. leaves. The HSCCC conditions were optimized by response surface methodology (RSM) considering two response indexes including retention of stationary phase and analysis time. The optimal HSCCC conditions were flow rate of 2.11 mL/min, revolution speed of 717 rpm, and temperature of 25℃, with a solvent system of ethyl acetate/methanol/water (10:1:10, v/v/v). The unseparated fractions obtained from HSCCC were subjected to preparative HPLC for further isolation. As a result, phloridzin (15.3 mg), isoquercitrin (2.1 mg), quercetin 3-O-xyloside (1.9 mg), quercetin-3-O-arabinoside (4.0 mg), and quercitrin (2.0 mg) were isolated from 200.0 mg extracts. The purities of these compounds were all above 92%. Their chemical structures were identified by mass spectrometer and nuclear magnetic resonance. The five isolated compounds were further investigated for their rat hippocampal neuroprotective effects against hydrogen peroxide-induced oxidative stress. No cytotoxicity was observed in all tested concentrations. While all five compounds except phloridzin showed significantly neurogenic activities and neuroprotective effects, especially at the concentration of 0.5 mg/L. These results demonstrate that RSM is a suitable technique for optimisation of HSCCC and the isolated polyphenols can be used as antioxidants in pharmaceutical and food products.

Protection against myocardial ischemia/reperfusion injury in mice by 3-caffeoylquinic acid isomers isolated from Saxifraga tangutica

The development of ischemic heart disease (IHD) involves a variety of pathophysiological responses, such as mitochondrial dysfunction. Many compounds with antioxidant activity isolated from natural products have been shown to have significant effects on the prevention and treatment of cardiovascular diseases. However, little is known about the palliative effects of 3-caffeoylquinic acid isomers isolated from Saxifraga tangutica (S. tangutica) on myocardial ischemia/reperfusion injury (MIRI). Three isomers of 3-caffeoylquinic acid were isolated from S. tangutica and identified as neochlorogenic acid (Fr2-4-1-1, 18.5 mg), chlorogenic acid (Fr2-5-1-1, 81.7 mg) and cryptochlorogenic acid (Fr2-5-2-1, 15.0 mg) using medium-pressure liquid chromatography-high-pressure two-dimensional liquid chromatography. An in vitro DPPH assay showed that cryptochlorogenic acid (CCGA), neochlorogenic acid (NCGA) and chlorogenic acid (CGA) (in order of activity from strongest to weakest) possessed superior antioxidant activity. Langendorff's in vitro model was utilized to explore the protective effects of 3 caffeoylquinic acid isomers against MIRI. The ex vivo MIRI assay demonstrated that CCGA significantly improved hemodynamic function (P < 0.05), hemodynamic function-related indices (LVDP, RPP, +dP/dt and -dP/dt), and cell morphology in I/R myocardium tissues. In addition, the results of western blot analysis showed that mitochondrial biogenesis was significantly increased in I/R myocardial tissues after treatment with CCGA. In contrast, the activities of CGA and NCGA were lower. This is the first demonstration of efficient preparative isolation of 3-caffeoylquinic acid isomers (CGA, NCGA and CCGA) from S. tangutica. CCGA may be a promising approach for the treatment of cardiac I/R injury, especially for the regulation of mitochondrial biogenesis after MIRI.

Ultrasound-Assisted Extraction of Paeonol from Moutan Cortex: Purification and Component Identification of Extract

Moutan Cortex (MC) is a traditional Chinese medicine that contains abundant medicinal components, such as paeonol, paeoniflorin, etc. Paeonol is the main active component of MC. In this study, paeonol was extracted from MC through an ultrasound-assisted extraction process, which is based on single-factor experiments and response surface methodology (RSM). Subsequently, eight macroporous resins of different properties were used to purify paeonol from MC. The main components of the purified extract were identified by ultra-performance liquid chromatography-quadrupole-time of flight-mass spectrometry (UPLC-Q-TOF-MS/MS). The results indicate the optimal parameters are as follows: liquid-to-material ratio 21:1 mL/g, ethanol concentration 62%, ultrasonic time 31 min, ultrasonic temperature 36 °C, ultrasonic power 420 W. Under these extraction conditions, the actual yield of paeonol was 14.01 mg/g. Among the eight tested macroporous resins, HPD-300 macroporous resin was verified to possess the highest adsorption and desorption qualities. The content of paeonol increased from 6.93% (crude extract) to 41.40% (purified extract) after the HPD-300 macroporous resin treatment. A total of five major phenolic compounds and two principal monoterpene glycosides were characterized by comparison with reference compounds. These findings will make a contribution to the isolation and utilization of the active components from MC.

Modeling and optimization of the protocol of complex chromatography separation of cyclooxygenase-2 inhibitors from Ganoderma lucidum spore

INTRODUCTION

The spores of the medicinal fungus Ganoderma lucidum possess hepatoprotective properties. The main components, triterpenes, are particularly beneficial, making the screening and preparation of active triterpenes from Ganoderma lucidum significant.

OBJECTIVES

We aimed to screen and verify cyclooxygenase-2 inhibitors from G. lucidum spores, establish a rapid online hyphenated technique for the preparation of active ingredients, and analyze the structures of the active ingredients.

METHODS

Ultrafiltration LC combined with an enzyme inhibition assay and molecular docking was employed to screen and evaluate cyclooxygenase-2 ligands, which were prepared by pressurized liquid extraction coupled online with countercurrent chromatography and semi-preparative LC. The structures of the compounds were identified by nuclear magnetic resonance spectroscopy.

RESULTS

Six cyclooxygenase-2 inhibitors, namely, ganoderic acids I, C₂ , G, B, and A and ganoderenic acid A, were screened and evaluated. They were prepared using the online hyphenated technique, following which their structures were identified.

CONCLUSION

This study provides opportunities for the discovery and development of new therapeutic drugs from other natural resources, as the present instrumental setup achieved efficient and systematic extraction and isolation of natural products compared with reference separation methods, thus exhibiting significant potential for industrial applications.

GUESS - A simple approach to accelerate optimization countercurrent separation

The generally useful estimate of solvent systems (GUESS) method, which is based on thin layer chromatography, is a simple and practical method for selecting solvent systems for countercurrent chromatography (CCC). However, it is rarely used for complex samples derived from natural products. In this study, GUESS was used for CCC solvent system selection and polarity-adjusted CCC separations of several fractions, which were obtained from a silica gel column containing complex compositions with a broad polarity from Salvia bowleyana Dunn. The GUESS method was performed on five fractions based on solvent systems in the n-hexane-ethyl acetate-methanol-water (HEMWat) family. Based on the GUESS results, the optimal solvent systems were selected for CCC separation. Twelve diterpenoids were obtained from the five silica gel column fractions of S. bowleyana Dunn using elution-extrusion countercurrent chromatography (EECCC). These demonstrate that GUESS guidance and the polarity adjustment of the solvent system accelerate the optimization of CCC separation conditions and simplify the process of accommodating a broad polarity of components in complicated mixture fractions. We therefore confirmed the feasibility and advantage of the GUESS method for complex natural chemical component separations.

The separation regularity of the three-phase solvent system of counter-current chromatography based on polarity parameter modeling

The three-phase solvent system of counter-current chromatography can separate compounds with a wide range of polarity, but there is no study of its separation regularity. Therefore, in this work, the separation regularity of the three-phase solvent system was initially investigated from the perspective of solvent polarities and compound polarities. The standard compounds covering a wide polarity range were selected, and three-phase solvent systems, n-hexane/methyl acetate/acetonitrile/water, and n-hexane/methyl tert-butyl ether/acetonitrile/water were used for modeling. The results showed that in the three-phase solvent system, the partition coefficient for the middle and lower phases (lgK_M/L) increased with increasing logP values in three intervals logP < 0, 0 < logP < 4, and logP > 4. In addition, the partition coefficient for the upper and middle phases (lgK_U/M) between the upper and middle phases of the small polarity compounds increases with increasing logP values. LogP vs lgK_M/L of 7 solvent systems were employed for the smoothing spline fit through a predictive model design of the curve fitting toolbox in MATLAB software, and good results were achieved. LogP versus lgK_M/L for n-hexane/methyl tert-butyl ether/acetonitrile/water solvent systems were used for the second-order power fit, and satisfactory results were obtained. The relationship between polarity parameters and separation case parameters was explored using a heat map approach. The separation regularity of the three-phase solvent system was preliminarily investigated. This regularity study gives hope of assistance to the chemists studying three-phase solvents and counter-current chromatography.

Receptor-ligand affinity-based screening and isolation of water-soluble 5-lipoxygenase inhibitors from Phellinus igniarius

We developed an efficient combination method for extraction, biological activity screening, and preparation of 5-lipoxygenase inhibitors from Phellinus igniarius. 5-Lipoxygenase inhibitors were rapidly screened using ultrafiltration-liquid chromatography based on the receptor-ligand affinity. Parameters such as extraction time, extraction times, and temperature as well as liquid-solid ratio were optimized using response surface methodology to maximize the total yield of the three target compounds. Next, bioactive ingredients were isolated using high-speed countercurrent chromatography and semi-preparative liquid chromatography. Three active ingredients, phellibaumin E, protocatechuic aldehyde, and osmundacetone, were obtained via ultrafiltration-liquid chromatography. Subsequently, the potential anti-dementia effects of the obtained bioactive compounds were verified using molecular docking assays. The above-mentioned target compounds, with purities of 98.82%, 98.89%, and 99.51%, respectively, were separated using a two-phase solvent system consisting of n-hexane-ethyl acetate-ethanol-water (2.5:2:0.75:3, v/v/v/v) coupled with semi-preparative liquid chromatography.

Online extraction and enrichment coupling with high-speed counter-current chromatography for effective and target isolation of antitumor anthraquinones from seeds of Cassia obtusifolia

Traditional bioassay-guided investigation of bioactive compounds from natural products comprises critical steps, such as extraction, repeated column separation, and activity assay. Thus, the development of facile, rapid, and efficient technology is critically important. Here, a HepG2 cell-based extraction method was first developed to rapidly screen potential antitumor compounds from the seeds ofCassia obtusifolia. Then, an online extraction and enrichment-high-speed counter-current chromatography (HSCCC) strategy was fabricated to facilely and efficiently isolate target antitumor compounds, which included direct extraction from solid C. obtusifolia, removal of polar interferences, enrichment of target compounds, and preparative isolation by HSCCC using flow rate stepwise increasing mode. After further purification by Sephadex LH-20 column, five antitumor anthraquinones, aurantio-obtusin, 1-desmethylaurantio-obtusin, chryso-obtusin, obtusin, and questin, were obtained for structural characterization and bioassay verification. The results may not only provide new perspectives for facile and rapid investigation of bioactive compounds from complex natural products, but also offer a scientific basis for the potential applications of C. obtusifolia.