Separation of natural products by centrifugal partition chromatography

An Unprecedented 4,8-Cycloeudesmane, Further New Sesquiterpenoids, a Triterpene, Steroids, and a Lignan from the Resin of Commiphora myrrha and Their Anti-Inflammatory Activity In Vitro

Myrrh has a long tradition in the treatment of inflammatory diseases. However, many of its (active) constituents are still unknown. In the present study, secondary metabolites were isolated from an ethanolic extract by various separation methods (liquid-liquid partition, silica and RP18 flash chromatography, CPC, and preparative HPLC), their structures were elucidated with NMR spectroscopy and mass spectrometry, and the selected compounds were tested for their effect on LPS-induced NO production by RAW 264.7 murine macrophages. Among the isolated substances are 17 sesquiterpenes (1-17) including the first 4,8-cycloeudesmane (1), a triterpene (38), two phytosterols (39, 40) and one lignan (43), which were previously unknown as natural products. Numerous compounds are described for the first time for the genus Commiphora. Eight of the eleven compounds tested (1, 29, 31, 32, 34-37) showed a statistically significant, concentration-dependent weak to moderate anti-inflammatory effect on NO production in the LPS-stimulated RAW 264.7 macrophages in vitro. For the reference substance, furanoeudesma-1,3-diene, an IC50 of 46.0 µM was determined. These sesquiterpenes might therefore be part of the multi-target molecular principles behind the efficacy of myrrh in inflammatory diseases.

Isolation of Anti-Prion Compounds from Curcuma phaeocaulis Valeton Extract

Prion diseases, known as a group of fatal neurodegenerative disorders caused by prions, remain incurable despite extensive research efforts. In a recent study, crude extract from Curcuma phaeocaulis Valeton (Cp) showed promising anti-prion efficacy in in vitro and in vivo models, prompting further investigation into their active compounds. We endeavored to identify the chemical constituents of the Cp extract and discover potential anti-prion agents. With the use of centrifugal partition chromatography (CPC), major constituents were isolated from the n-hexane (HX) fraction of the extract in a single step. Spectroscopic analysis confirmed the presence of curcumenone, curcumenol, and furanodienone. Subsequent efficacy testing in a cell culture model of prion disease identified curcumenol and furanodienone as active compounds. This study underscores the potential of natural products in the search for effective treatments against prion diseases.

Terpenoids from Myrrh and Their Cytotoxic Activity against HeLa Cells

The oleo-gum resin of Commiphora myrrha (Nees) Engl. has a long history of medicinal use, although many of its constituents are still unknown. In the present investigation, 34 secondary metabolites were isolated from myrrh resin using different chromatographic techniques (silica flash chromatography, CPC, and preparative HPLC) and their structures were elucidated with NMR spectroscopy, HRESIMS, CD spectroscopy, and ECD calculations. Among the isolated substances are seven sesquiterpenes (1-7), one disesquiterpene (8), and two triterpenes (23, 24), which were hitherto unknown, and numerous substances are described here for the first time for C. myrrha or the genus Commiphora. Furthermore, the effects of selected terpenes on cervix cancer cells (HeLa) were studied in an MTT-based in vitro assay. Three triterpenes were observed to be the most toxic with moderate IC₅₀ values of 60.3 (29), 74.5 (33), and 78.9 µM (26). Due to the different activity of the structurally similar triterpenoids, the impact of different structural elements on the cytotoxic effect could be discussed and linked to the presence of a 1,2,3-trihydroxy substructure in the A ring. The influence on TNF-α dependent expression of the intercellular adhesion molecule 1 (ICAM-1) in human microvascular endothelial cells (HMEC-1) was also tested for 4-6, 9-11, 17, 18, 20, and 27 in vitro, but revealed less than 20% ICAM-1 reduction and, therefore, no significant anti-inflammatory activity.

Marine algal flavonoids and phlorotannins; an intriguing frontier of biofunctional secondary metabolites

Algae are the oldest representatives of the plant world with reserves exceeding hundreds of millions of tons in the world's oceans. Currently, a growing interest is placed toward the use of algae as feedstocks for obtaining numerous natural products. Algae are a rich source of polyphenols that possess intriguing structural diversity. Among the algal polyphenols, phlorotannins, which are unique to brown seaweeds, and have immense value as potent modulators of biochemical processes linked to chronic diseases. In algae, flavonoids remain under-explored compared to other categories of polyphenols. Both phlorotannins and flavonoids are inclusive of compounds indicating a wide structural diversity. The present paper reviews the literature on the ecological significance, biosynthesis, structural diversity, and bioactivity of seaweed phlorotannins and flavonoids. The potential implementation of these chemical entities in functional foods, cosmeceuticals, medicaments, and as templates in drug design are described in detail, and perspectives are provided to tackle what are perceived to be the most momentous challenges related to the utilization of phlorotannins and flavonoids. Moving beyond: industrial biotechnology applications, metabolic engineering, total synthesis, biomimetic synthesis, and chemical derivatization of phlorotannins and flavonoids could broaden the research perspectives contributing to the health and economic up-gradation.

Sesquiterpenes from Myrrh and Their ICAM-1 Inhibitory Activity In Vitro

By using various chromatographic steps (silica flash, CPC, preparative HPLC), 16 sesquiterpenes could be isolated from an ethanolic extract of myrrh resin. Their chemical structures were elucidated by 1D and 2D NMR spectroscopy and HRESIMS. Among them, six previously unknown compounds (1-6) and another four metabolites previously not described for the genus Commiphora (7, 10, 12, 13) could be identified. Sesquiterpenes 1 and 2 are novel 9,10-seco-eudesmanes and exhibited an unprecedented sesquiterpene carbon skeleton, which is described here for the first time. New compound 3 is an 9,10 seco-guaian and the only peroxide isolated from myrrh so far. Compounds 1, 2, 4, 7-9, 11, 13-16 were tested in an ICAM-1 in vitro assay. Compound 7, as well as the reference compound furanoeudesma-1,3-diene, acted as moderate inhibitors of this adhesion molecule ICAM-1 (IC50: 44.8 and 46.3 μM, respectively). These results give new hints on the activity of sesquiterpenes with regard to ICAM-1 inhibition and possible modes of action of myrrh in anti-inflammatory processes.

Optimized conversion of antiproliferative lignans pinoresinol and epipinoresinol: Their simultaneous isolation and identification by centrifugal partition chromatography and high performance liquid chromatography

High amount of the valuable lignan pinoresinol (PR) was determined in Carduus nutans fruit (7.8mg/g) for the first time. A preparative separation method using two consecutive, identical steps of centrifugal partition chromatography (CPC) was developed in order (i) to isolate PR and (ii) to subsequently isolate PR and its 7' epimer epipinoresinol (EPR) simultaneously after an optimized acid treatment which resulted in PR epimerization forming equal amounts of PR and EPR, from C. nutans fruit. As optimal conditions, a two-phase solvent system consisting of methyl tert-butyl ether:acetone:water (4:3:3, v/v/v) for CPC separation, and an acid treatment performed at 50°C for 30min for the epimerization were applied. Thus, 33.7mg and 32.8mg PR and EPR, in as high as 93.7% and 92.3% purity, were isolated from 10.0gC. nutans fruit, representing 86.4% and 84.1% efficiency, respectively. Conversion characteristic of PR and EPR in acidic medium, determined as a function of time and temperature of acid treatment provides their unambiguous identification by on-line high performance liquid chromatography (HPLC). Antiproliferative assay of isolated PR and EPR in two different types of colon cancer cell lines (HCT116 and SW480) confirmed that both epimers caused a more significant decrease of viability in HCT116 cells than in SW480 cells, suggesting their similar mechanism of antiproliferative action.

Isolation of Methoxyfuranocoumarins From Ammi majus by Centrifugal Partition Chromatography

Pure methoxyfuranocoumarins were isolated from Ammi majus L. by use of low-pressure column chromatography (LPCC) followed by centrifugal partition chromatography (CPC). The concentrated petroleum ether extract from fruits of A. majus was fractionated on a silica gel column using a gradient of ethyl acetate in dichloromethane (0-80%, v/v). Coumarin-rich fractions were analyzed by thin-layer chromatography (TLC) and high-performance liquid chromatography with diode array detection (HPLC/DAD). Xanthotoxin (8-MOP) and isopimpinellin (isoP), structurally similar compounds, were isolated in one fraction (FR6). To avoid multistep and long-lasting TLC preparation, optimization of CPC conditions has been performed. In one run, an effective separation of 8-MOP and isoP was achieved. The two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (10 : 8 : 10 : 9; v/v) in an ascending mode (the aqueous phase was a stationary phase, and the organic phase was a mobile phase), with flow rate 3 mL/min and rotation speed 1,600 r.p.m., was used. The identification and high purities of isolated 8-MOP (98.7%) and isoP (100%) were confirmed by HPLC/DAD assay, when compared with standards. The developed CPC method could be applied to the effective isolation of 8-MOP and isoP from plant extracts. The high purity of obtained compounds makes possible further exploitation of these components in biological studies.

Preparative isolation and purification of phlorotannins from Ecklonia cava using centrifugal partition chromatography by one-step

Various bioactive phlorotannins of Ecklonia cava (e.g., dieckol, eckol, 6,6-bieckol, phloroglucinol, phloroeckol, and phlorofucofuroeckol-A) are reported. However, their isolation and purification are not easy. Centrifugal partition chromatography (CPC) can be used to efficiently purify the various bioactive-compounds efficiently from E. cava. Phlorotannins are successfully isolated from the ethyl acetate (EtOAc) fraction of E. cava by CPC with a two-phase solvent system comprising n-hexane:EtOAc:methanol:water (2:7:3:7, v/v) solution. The dieckol (fraction I, 40.2mg), phlorofucofuroeckol-A (fraction III, 31.1mg), and fraction II (34.1mg) with 2,7-phloroglucinol-6,6-bieckol and pyrogallol-phloroglucinol-6,6-bieckol are isolated from the crude extract (500 mg) by a one-step CPC system. The purities of the isolated dieckol and phlorofucofuroeckol-A are ⩾90% according to high performance liquid chromatography (HPLC) and electrospray ionization multi stage tandem mass spectrometry analyses. The purified 2,7-phloroglucinol-6,6-bieckol and pyrogallol-phloroglucinol-6,6-bieckol are collected from fraction II by recycle-HPLC. Thus, the CPC system is useful for easy and simple isolation of phlorotannins from E. cava.

Counter-current chromatography for the separation of terpenoids: a comprehensive review with respect to the solvent systems employed

Natural products extracts are commonly highly complex mixtures of active compounds and consequently their purification becomes a particularly challenging task. The development of a purification protocol to extract a single active component from the many hundreds that are often present in the mixture is something that can take months or even years to achieve, thus it is important for the natural product chemist to have, at their disposal, a broad range of diverse purification techniques. Counter-current chromatography (CCC) is one such separation technique utilising two immiscible phases, one as the stationary phase (retained in a spinning coil by centrifugal forces) and the second as the mobile phase. The method benefits from a number of advantages when compared with the more traditional liquid-solid separation methods, such as no irreversible adsorption, total recovery of the injected sample, minimal tailing of peaks, low risk of sample denaturation, the ability to accept particulates, and a low solvent consumption. The selection of an appropriate two-phase solvent system is critical to the running of CCC since this is both the mobile and the stationary phase of the system. However, this is also by far the most time consuming aspect of the technique and the one that most inhibits its general take-up. In recent years, numerous natural product purifications have been published using CCC from almost every country across the globe. Many of these papers are devoted to terpenoids-one of the most diverse groups. Naturally occurring terpenoids provide opportunities to discover new drugs but many of them are available at very low levels in nature and a huge number of them still remain unexplored. The collective knowledge on performing successful CCC separations of terpenoids has been gathered and reviewed by the authors, in order to create a comprehensive document that will be of great assistance in performing future purifications.

Preparative isolation of sargachromanol E from Sargassum siliquastrum by centrifugal partition chromatography and its anti-inflammatory activity

Centrifugal partition chromatography (CPC) can be used to isolate various bioactive compounds from natural materials by one-step. We confirmed antioxidative compounds existed in chloroform (CHCl3) fraction of Sargassum siliquastrum using online-HPLC. Fractions (A, B, C, D and E) were separated from the CHCl3 fraction by preparative CPC (n-hexane:ethyl acetate:methanol:water, 5:5:7:3, v/v). In this study, we proved that the isolated compounds exhibit anti-inflammatory activities using lipopolysaccharide (LPS) stimulated RAW 264.7 macrophages. The fraction A which exhibited the strongest inhibitory effect on nitric oxide (NO) production level, was confirmed as sargachromanol E by LC-MS-ESI, (1)H NMR and (13)C NMR data. The sargachromanol E significantly reduced the inflammatory response in LPS induced macrophages, decreasing LPS-induced transcription factor of pro-inflammatory cyclooxygenase-2, NO synthase, phosphate P38, phosphate ERK1/2, LPS-stimulated tumor-necrosis factor alpha, interleukin-1 beta and prostaglandin E2 release. In conclusion, it was suggested that sargachromanol E inhibited inflammation in LPS induced RAW 264.7 cells via MAPK pathway.

Intermittent counter-current extraction-Equilibrium cell model, scaling and an improved bobbin design

This paper describes an equilibrium cell model for intermittent counter-current extraction that is analytically solved for the first time for continuous sample injection between a pair of columns. The model is compared with practice for injections of a model mixture of compounds on a standard high-performance counter-current chromatography instrument giving good agreement for compound elution order and the times to maximum concentration for the eluted components. An improved design of end fittings for the counter-current chromatography bobbins is described which permits on-column switching of the mobile and stationary phases. This on-column switching successfully eliminates the displaced stationary phase seen in fractions when operating ICcE with standard flying leads and gives a 6% reduction in the retention time of compounds and improved resolution due to the elimination of the time delay required to pump the previous mobile phase from standard flying leads.

Kenganthranol F, a new Anthranol from Psorospermum aurantiacum

A new anthranol, kenganthranol F, was isolated from the ethyl acetate extracts of the seeds and the whole plant of the Cameroonian plant Psorospermum aurantiacum (Hypericaceae), together with fifteen known compounds viz., ferruginin B, vismin, vismion D, haronginanthrone, kenganthraquinone, kenganthranol B and kenganthranol E isolated from the fruits and 3-geranyloxyemodinanthrone, 2-geranylemodin, bianthrone A1, vismione D, 1,8-dihydroxy- 3-geranyloxy-6-methylanthraquinone, vismione M, vismiaquinone, vismiaquinone C being isolated from the whole plant. The structure of the new isomer of kenganthranol F was determined to be 1,8,10-trihydroxy-3,4-[2,2-dimethyldihydropyrano]-6-methyl-2,5-bis-(3,3-dimethylallyl)-anthrone.

Large scale purification of B-type fumonisins using centrifugal partition chromatography (CPC)

For toxicological studies of B-type fumonisin in animals, high amounts of pure fumonisins are needed. In the past, several methods for the isolation and purification of fumonisins have been published, stating the problem of high losses of fumonisins during chromatography on solid phases. In this manuscript we describe a new approach based on liquid-liquid partition techniques using centrifugal partition chromatography in combination with ion exchange chromatography for the large-scale isolation of B-type fumonisins with good recovery rates, minimizing losses of fumonisins during the purification. A batch of cultures grown on solid media of 2 kg maize yields approximately 1 g of pure fumonisins with a purity of >98%.

One-step isolation of γ-oryzanol from rice bran oil by non-aqueous hydrostatic countercurrent chromatography

The value-added γ-oryzanol was purified in one step from crude rice bran oil (RBO) using a preparative hydrostatic countercurrent chromatography (hydrostatic CCC) method, operating in the dual mode. The fractionation was performed using a non-aqueous biphasic solvent system consisting of heptane-acetonitrile-butanol (1.8:1.4:0.7, v/v/v), leading rapidly to the target compounds. Transfer of the analytical CCC method to large-scale isolation was also carried out yielding a high quantity-high purity fraction of γ-oryzanol. In addition, a fraction of hydroxylated triterpene alcohol ferulates (polar γ-oryzanol) was clearly separated and obtained. Furthermore, a fast HPLC-APCI(±)-HRMS method was developed and applied for the identification of γ-oryzanol as well as the polar γ-oryzanol in RBO and the resulting fractions. The purity of γ-oryzanol fraction was estimated as 97% based on HPLC-APCI-HRMS analysis.

An In-House Built Semiautomated Countercurrent Chromatography Workstation

An elution—extrusion countercurrent chromatography workstation was designed and built in-house for fractionating crude natural product extracts. The engineering efforts of this project included both custom hardware and software integration. The resulting workstation operates four individual chromatography coils for natural product extract separation and purification. The workstation offers the ability to collect fractions into 16 × 100 mm borosilicate glass test tubes or allows for stream splitting of the coil effluent so that the fractions can be collected into both 16 × 100 mm borosilicate test tubes and a 96-well microplate. Solvent pumping for each of the chromatography columns is achieved through the use of syringe pumps. The workstation is controlled though a custom control software application, C_Cubed, written in Visual Basic 6.0 (VB6). Software architecture consists of three levels. At the lowest level, there are ActiveX dll device drivers that interface with the physical hardware. The middle layer is a custom scheduler allowing for multitasking of instrument movements. The upper level is composed of a Wizard-style user interface that mimics the scientific workflow. Finally, by using a software timer the software application was written to operate on a single thread, but exhibit multithreaded behavior.

One step purification of flavanone glycosides from Poncirus trifoliata by centrifugal partition chromatography

Flavanone glycosides were successfully separated from the crude extract of Poncirus trifoliata by preparative centrifugal partition chromatography with a two-phase solvent system composed of ethyl acetate-acetonitrile-water (3:2:5, v/v/v). Naringin (50.0 mg), neoponcirin (16.8 mg), and poncirin (71.9 mg) were purified from the 524 mg crude extract in only one step. The purities of the isolated compounds were determined to be over 90% by HPLC analysis and their structures were elucidated by (1)H NMR, (13)C NMR, and ESI-MS.

Preparative isolation and purification of sinomenine fromSinomenium acutum by centrifugal partition chromatography

Preparative centrifugal partition chromatography (CPC) was successfully carried out for the separation of sinomenine from the methanolic extract of Sinomenium acutum stems and rhizomes. The optimum two-phase solvent system of CPC was composed of n-hexane/ethyl acetate/methanol/water at a volume ratio of 1:6:2:8 (v/v/v/v) with 0.1% triethylamine (TEA). Preparative CPC yielded 44.3 mg of sinomenine from 400 mg of MeOH extract with a purity of 96.9%.

Preparative isolation and purification of geniposide from gardenia fruits by centrifugal partition chromatography

The iridoid glycoside, geniposide was purified by centrifugal partition chromatography (CPC) with a two-phase solvent system composed of ethyl acetate:isopropanol:water (3:2:5, v/v) from an 80% methanolic extract of fruits of Gardenia jasminoides. Preparative CPC yielded 56.2 mg of geniposide in a one-step separation of 500 mg of extract, with a purity of 95% as determined by HPLC. Isolated geniposide was identified from its 1H-NMR, 13C-NMR and MS spectra.

Preparative isolation and purification of atractylon and atractylenolide III from the Chinese medicinal plantAtractylodes macrocephala by high-speed counter-current chromatography

The medicinal plant Atractylodes macrocephala (Baizhu in Chinese) has been widely used in traditional Chinese medicine for energy and stomach complaints, treatment of dyspepsia and anorexia, anti-inflammation, anticancer and for increasing assimilation. A high-speed counter-current chromatography (HSCCC) method was developed for the preparative separation and purification of two main bioactive components, namely, atractylon and atractylenolide III from A. macrocephala by using light petroleum (60-90 degrees C)-ethyl acetate-ethanol-water (4:1:4:1 v/v) as the two-phase solvent system in dual-mode elution. Compared with the separation using the normal-mode elution, the dual-mode HSCCC can be achieved with shorter elution time. Atractylenolide III (32.1 mg) at 99.0% purity and 319.6 mg atractylon at 97.8% purity could be obtained from 1000 mg crude sample in a single run. The recoveries of atractylenolide III and atractylon were 95.4 and 92.6%, respectively.

A preparative isolation and purification of arctigenin and matairesinol fromForsythia koreana by centrifugal partition chromatography

Centrifugal partition chromatography was applied to separate arctigenin and matairesinol from Forsythia koreana extract with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (5:5:5:5 v/v). Using this method, arctigenin and matairesinol were successfully separated from partially purified F. koreana extracts in only one step. The purities of isolated compounds were determined to be over 90% by HPLC analysis.

Isolation of secondary metabolites from roots of Plumbago auriculata Lam. by countercurrent chromatography

Centrifugal liquid-liquid partition chromatography presents significant advantages for the separation and purification of plant metabolites owing to the short operational time of the process and the elimination of possible irreversible adsorption of compounds. The crude chloroform extract from roots of Plumbago auriculata was analysed by countercurrent chromatography using hexane:ethyl acetate:methanol:water (40:10:10:2, v/v) as solvent system. The isolation of the naphthoquinones plumbagin and epi-isoshinanolone, the steroids sitosterol and 3-O-glucosylsitosterol, plumbagic and palmitic acids was easily achieved. Naphthoquinones are typical components of Plumbago species and they show interesting biological activities.

Analytical aspects of drugs of natural origin

The current importance of drugs of natural origin and their different phytotherapeutical preparations are mentioned. Analytical aspects related to vegetable drugs and their extracts are discussed. An overview is given on procedures used for the isolation of reference compounds, sample preparation for high-performance liquid chromatographic analysis, identification of vegetable drugs and detection of adulterants. The different approaches currently employed for the standardization of extracts are presented. The various aspects are discussed with the aid of illustrative examples.