Countercurrent chromatography separation of saponins by skeleton type from Ampelozizyphus amazonicus for off-line ultra-high-performance liquid chromatography/high resolution accurate mass spectrometry analysis and characterisation

A novel strategy by combining foam fractionation with high-speed countercurrent chromatography for the rapid and efficient isolation of antioxidants and cytostatics from Camellia oleifera cake

Camellia oleifera cake is a by-product, which is rich in functional chemical components. However, it is typically used as animal feed with no commercial value. The purpose of this study was to isolate and identify compounds from Camellia oleifera cake using a combination of foam fractionation and high-speed countercurrent chromatography (HSCCC) and to investigate their biological activities. Foam fractionation with enhanced drainage through a hollow regular decahedron (HRD) was first established for simultaneously enriching flavonoid glycosides and saponins for further separation of target compounds. Under suitable operating conditions, the introduction of HRD resulted in a threefold increase in enrichment ratio with no negative effect on recovery. A novel elution-extrusion countercurrent chromatography (EECCC) coupled with the consecutive injection mode was established for the successful simultaneous isolation of flavonoid glycosides and saponins. As a result, 38.7 mg of kaemferol-3-O-[2-O-D-glucopyranosyl-6-O-α-L-rhamnopyranosyl]-β-D-glucopyranoside (purity of 98.17%, FI), 70.8 mg of kaemferol-3-O-[2-O-β-D-xylopyranosyl-6-O-α-L-rhamnopyranosyl]-β-D-glucopyranoside (purity of 97.52%, FII), and 560 mg of an oleanane-type saponin (purity of 92.32%, FIII) were separated from the sample (900 mg). The present study clearly showed that FI and II were natural antioxidants (IC50 < 35 μg/mL) without hemolytic effect. FIII displayed the effect of inhibiting Hela cell proliferation (IC50 < 30 μg/mL). Further erythrocyte experiments showed that this correlated with the extremely strong hemolytic effect of FIII. Overall, this study offers a potential strategy for efficient and green isolation of natural products, and is beneficial to further expanding the application of by-products (Camellia oleifera cake) in food, cosmetics, and pharmacy.

Isolation and Identification of 12-Deoxyphorbol Esters from Euphorbia resinifera Berg Latex: Targeted and Biased Non-Targeted Identification of 12-Deoxyphorbol Esters by UHPLC-HRMSE

Diterpenes from the Euphorbia genus are known for their ability to regulate the protein kinase C (PKC) family, which mediates their ability to promote the proliferation of neural precursor cells (NPCs) or neuroblast differentiation into neurons. In this work, we describe the isolation from E. resinifera Berg latex of fifteen 12-deoxyphorbol esters (1-15). A triester of 12-deoxy-16-hydroxyphorbol (4) and a 12-deoxyphorbol 13,20-diester (13) are described here for the first time. Additionally, detailed structural elucidation is provided for compounds 3, 5, 6, 14 and 15. The absolute configuration for compounds 3, 4, 6, 13, 14 and 15 was established by the comparison of their theoretical and experimental electronic circular dichroism (ECD) spectra. Access to the above-described collection of 12-deoxyphorbol derivatives, with several substitution patterns and attached acyl moieties, allowed for the study of their fragmentation patterns in the collision-induced dissociation of multiple ions, without precursor ion isolation mass spectra experiments (HRMSE), which, in turn, revealed a correlation between specific substitution patterns and the fragmentation pathways in their HRMSE spectra. In turn, this allowed for a targeted UHPLC-HRMSE analysis and a biased non-targeted UHPLC-HRMSE analysis of 12-deoxyphorbols in E. resinifera latex which yielded the detection and identification of four additional 12-deoxyphorbols not previously isolated in the initial column fractionation work. One of them, identified as 12-deoxy-16-hydroxyphorbol 20-acetate 13-phenylacetate 16-propionate (20), has not been described before.

Anti-SARS-CoV-2 Activity of Ampelozizyphus amazonicus (Saracura-Mirá): Focus on the Modulation of the Spike-ACE2 Interaction by Chemically Characterized Bark Extracts by LC-DAD-APCI-MS/MS

Traditional medicine shows several treatment protocols for COVID-19 based on natural products, revealing its potential as a possible source of anti-SARS-CoV-2 agents. Ampelozizyphus amazonicus is popularly used in the Brazilian Amazon as a fortifier and tonic, and recently, it has been reported to relieve COVID-19 symptoms. This work aimed to investigate the antiviral potential of A. amazonicus, focusing on the inhibition of spike and ACE2 receptor interaction, a key step in successful infection. Although saponins are the major compounds of this plant and often reported as its active principles, a polyphenol-rich extract was the best inhibitor of the spike and ACE2 interaction. Chemical characterization of A. amazonicus bark extracts by LC-DAD-APCI-MS/MS before and after clean-up steps for polyphenol removal showed that the latter play an essential role in maintaining this activity. The effects of the extracts on viral replication were also assessed, and all samples (aqueous and ethanol extracts) demonstrated in vitro activity, inhibiting viral titers in the supernatant of Calu-3 cells after 24 hpi. By acting both in the SARS-CoV-2 cell entry process and its replication, A. amazonicus bark extracts stand out as a multitarget agent, highlighting the species as a promising candidate in the development of anti-SARS-CoV-2 drugs.

Saracura-Mirá, a Proposed Brazilian Amazonian Adaptogen from Ampelozizyphus amazonicus

The Amazon Forest is known all over the world for its diversity and exuberance, and for sheltering several indigenous groups and other traditional communities. There, as well as in several other countries, in traditional medical systems, weakness, fatigue and debility are seen as limiting health conditions where medicinal plants are often used in a non-specific way to improve body functions. This review brings together literature data on Ampelozizyphus amazonicus, commonly known in Brazil as "saracura-mirá" and/or "cerveja de índio", as an Amazonian adaptogen, including some contributions from the authors based on their ethnographic and laboratory experiences. Topics such as botany, chemistry, ethnopharmacological and pharmacological aspects that support the adaptogen character of this plant, as well as cultivation, market status and supply chain aspects are discussed, and the gaps to establish "saracura-mirá" as an ingredient for the pharmaceutical purposes identified. The revised data presented good scientific evidence supporting the use of this Amazonian plant as a new adaptogen. Literature data also reveal that a detailed survey on natural populations of this plant is needed, as well as agronomical studies that could furnish A. amazonicus bark as a raw material. Another important issue is the lack of developed quality control methods to assure its quality assessment.

On-line coupling pressurised liquid extraction with two-dimensional counter current chromatography for isolation of natural acetylcholinesterase inhibitors from Astragalus membranaceus

INTRODUCTION

Radix Astragali, the dried root of Astragalus membranaceus (Fish.) Bge. (family Fabaceae), which is known as Huangqi in China, has been proven to be an immunostimulant, diuretic, antidiabetic, analgesic, and it has also been used as a health food supplement in some Asian populations and also serves as a lead herb in many traditional Chinese medicine formulations as well as in Chinese ethnic tonifying soups.

OBJECTIVE

Screening and purification of bioactive compounds from natural products is challenging work due to their complexity. We present the first report on the use of pressurised liquid extraction and on-line two-dimensional counter current chromatography as an efficient medium for scaled-up extraction and separation of six bioactive compounds from Astragalus membranaceus.

METHOD

We applied the established method with ultrafiltration-liquid chromatography to screen acetylcholinesterase inhibitors, which were then evaluated and confirmed for anti-Alzheimer activity using PC12 cell model.

RESULTS

Six major compounds, namely, calycosin-7-O-β-d-glucoside, pratensein-7-O-β-d-glucoside, formononetin-7-O-β-d-glucoside, calycosin, genistein, and formononetin, with acetylcholinesterase binding affinities were identified and isolated from the raw plant materials via two sets of n-hexane/ethyl acetate/0.2% acetic acid (first-stage counter current chromatography) and n-hexane/ethyl acetate/methanol/water (second-stage counter current chromatography) solvent systems: 1.87:1.0:1.33 and 5.62:1.0:2.42:5.25, v/v/v/v, which were optimised by a mathematical model.

CONCLUSION

Therefore, a useful platform for the large-scale production of bioactive and nutraceutical ingredients was developed herein. With the on-line system developed here, we present a feasible, selective, and effective strategy for rapid screening and identification of enzyme inhibitors from complex mixtures.

Mass spectrometry as a tool for the dereplication of saponins from Ampelozizyphus amazonicus Ducke bark and wood

INTRODUCTION

Mass spectrometry in natural products research has been used as a first step to identify possible chemical structures and to guide subsequent efforts to isolate novel compounds. Preparations of Ampelozizyphus amazonicus Ducke (AA) are known for their high content of saponins, especially dammarane-type triterpenoid aglycones. In the Amazon, where it is known as "saracura-mirá", roots and bark are widely used for the treatment and prevention of malaria, while the wood is discarded. The extract prepared from the wood is also saponin-rich, but its exact chemical composition has not been described.

OBJECTIVE

This study provides information on the chemical profiling and tentative structural identification of the major compounds (saponins) present in aqueous and ethanol extracts of bark and wood of AA by mass spectrometry.

METHODS

The strategy used to identify compounds present in all samples was ultra-high-performance liquid chromatography with an ultraviolet detector coupled to tandem mass spectrometry (UHPLC-UV-MS/MS) for the analysis of fragmentation patterns through product ion scan using MZmine 2 software. Also, direct sample injection and electrospray ionisation combined with high-resolution mass spectrometry (DI-ESI-HRMS) measurements were performed.

RESULTS

The extracts showed chemical similarity, and 95 saponins were tentatively identified in AA wood and bark, including 73 which are described for the first time as tentative structures for this plant species.

CONCLUSION

This research describes a useful method for the fast and simultaneous tentative identification of major saponins in AA, contributing to the study of the chemical properties of this genus and family. Furthermore, it demonstrates the importance of the qualitative dereplication process, allowing a straightforward way to propose the tentative identification of compounds.

Analytical, Preparative, and Industrial-Scale Separation of Substances by Methods of Countercurrent Liquid-Liquid Chromatography

Countercurrent liquid-liquid chromatographic techniques (CCC), similar to solvent extraction, are based on the different distribution of compounds between two immiscible liquids and have been most widely used in natural product separations. Due to its high load capacity, low solvent consumption, the diversity of separation methods, and easy scale-up, CCC provides an attractive tool to obtain pure compounds in the analytical, preparative, and industrial-scale separations. This review focuses on the steady-state and non-steady-state CCC separations ranging from conventional CCC to more novel methods such as different modifications of dual mode, closed-loop recycling, and closed-loop recycling dual modes. The design and modeling of various embodiments of CCC separation processes have been described.

Rapid Recognition and Targeted Isolation of Anti-HIV Daphnane Diterpenes from Daphne genkwa Guided by UPLC-MSn

Daphnane diterpenes with a 5/7/6-tricyclic ring system exhibit potent anti-HIV activity but are found in low abundance as plant natural products. In this study, an effective approach based on mass spectrometric fragmentation pathways was conducted to specifically recognize and isolate anti-HIV compounds of this type from Daphne genkwa. Briefly, the fragmentation pathways of reference analogues were elucidated based on characteristic ion fragments of m/z 323 → 295 → 267 or m/z 253 → 238 → 197 by ultra-high-performance liquid chromatography-ion trap tandem mass spectrometry (UPLC-IT-MSⁿ) and then applied to the differentiations of substances with or without an oxygenated group at C-12. Twenty-seven daphnane diterpenes were successfully recognized from a petroleum ether extract of D. genkwa, including some potential new compounds and isomers that could not be identified accurately only from the ion fragments. Further separation of these target compounds using high-speed countercurrent chromatography (HSCCC) and preparative HPLC led to the isolation of three new (11, 25, and 27) and 14 known compounds, whose structures were identified and confirmed based on MS, NMR, and electronic circular dichroism (ECD) spectroscopy. The isolates exhibited anti-HIV activities at nanomolar concentrations. The results demonstrated that this strategy is feasible and reliable to rapidly recognize and isolate daphnane diterpenes from D. genkwa.

Structure Elucidation, Conformation, and Configuration of Cytotoxic 6-Heptyl-5,6-dihydro-2 H-pyran-2-ones from Hyptis Species and Their Molecular Docking to α-Tubulin

Cytotoxic 6-heptyl-5,6-dihydro-2 H-pyran-2-ones are chemical markers of Hyptis (Lamiaceae) and are responsible for some of the therapeutic properties of species with relevance to traditional medicine. The present investigation describes the isolation of known pectinolides A-C (1-3), in addition to the new pectinolides I-M (4-8), from two Mexican collections of H. pectinata by HPLC. The novel biosynthetically related monticolides A (9) and B (10) were also isolated by high-speed countercurrent chromatography from H. monticola, an endemic species of the Brazilian southeastern high-altitude regions. A combination of chemical correlations, chiroptical measurements, and Mosher ester NMR analysis was used to confirm their absolute configuration. The utility of DFT-NMR chemical shifts and J_H-H calculations was assessed for epimer differentiation. Molecular docking studies indicated that 6-heptyl-5,6-dihydro-2 H-pyran-2-ones have a high affinity for the pironetin-binding site of α-tubulin, which may be a possible mechanism contributing to the cytotoxic potential of these small and flexible molecules.

Countercurrent separation assisted identification of two mammalian steroid hormones in Vitex negundo

Countercurrent separation (CCS) has been widely used for the separation of high abundance compounds. However, the identification of low abundance compounds, such as mammalian steroid hormones, from natural sources is still a challenging task. A mixture of 14 human steroid hormone reference compounds was prepared for the development of a CCS enrichment strategy. The TLC-based GUESS (Generally Useful Estimate of Solvent Systems) method along with partitioning experiments were implemented to develop a process for the enrichment of these low abundance compounds with CCS. The application of CCS to the steroid hormone enrichment of Vitex negundo extracts was demonstrated by the identification of progesterone and estriol. This method provides a CCS-driven strategy to mine plant sources for low abundance compounds.

An easy-to-use calculating machine to simulate steady state and non-steady-state preparative separations by multiple dual mode counter-current chromatography with semi-continuous loading of feed mixtures

Multiple dual mode counter-current chromatography (MDM CCC) separation processes with semi-continuous large sample loading consist of a succession of two counter-current steps: with "x" phase (first step) and "y" phase (second step) flow periods. A feed mixture dissolved in the "x" phase is continuously loaded into a CCC machine at the beginning of the first step of each cycle over a constant time with the volumetric rate equal to the flow rate of the pure "x" phase. An easy-to-use calculating machine is developed to simulate the chromatograms and the amounts of solutes eluted with the phases at each cycle for steady-state (the duration of the flow periods of the phases is kept constant for all the cycles) and non-steady-state (with variable duration of alternating phase elution steps) separations. Using the calculating machine, the separation of mixtures containing up to five components can be simulated and designed. Examples of the application of the calculating machine for the simulation of MDM CCC processes are discussed.

Characterisation of nutraceutical compounds from different parts of particular species of Citrus sinensis 'Ovale Calabrese' by UHPLC-UV-ESI-HRMS

Consumers are aware of diet causing health problems and therefore there is an increased demand for natural ingredients that are expected to be safe and health-promoting. Many of these compounds belong to the class of flavonoids and can be divided into these five groups: flavanones, flavones, flavonols, flavanols, isoflavones and anthocyanidins. Extracts from citrus fruits are usually used as functional ingredients for several products. The aim of this paper was to develop an UHPLC-UV-ESI-HRMS method to define the metabolite profile of different parts of citrus fruit, of a particular cultivar called 'Ovale Calabrese', and in its main by-products. The high resolution mass spectrometry analysis allowed the identification of 27 compounds belonging to the classes of flavonoids and terpenoids. The high contents of phytochemical compounds, reveal the potential use of the 'Ovale Calabrese' as a rich source of nutraceutical compounds.

The 9th International Countercurrent Chromatography Conference held at Dominican University, Chicago, USA, August 1-3, 2016

The 9th International Countercurrent Chromatography Conference (CCC 2016) was held at Dominican University near Chicago, IL (USA), from August 1st-3rd, 2016. The biennial CCC 20XX conferences provide an opportunity for countercurrent chromatography and centrifugal partition chromatography (CCC/CPC) manufactures, marketers, theorists, and research scientists to gather together socially, learn from each other, and advance countercurrent separation technology. A synopsis of the conference proceedings as well as a series of short reviews of the special edition articles is included in this document. Many productive discussions and collegial conversation at CCC 2016 attested to the liveliness, connectivity, and productivity of the global countercurrent research community and bodes well for the success of the 10th conference at the University of Braunschweig, Germany on August 1-3, 2018.