Preparative high-speed counter-current chromatography separation of grape seed proanthocyanidins according to degree of polymerization

The biological functions of proanthocyanidin and its application in pig production

Proanthocyanidins (PACs) are natural polyphenolic compounds widely distributed in various plants, which are mixtures of oligomers and polymers formed by the polymerization of different numbers of catechins and epicatechins. PACs exhibit a range of biological activities, including antioxidant, anti-inflammatory, anti-cancer, anti-atherosclerotic, hypoglycemic, and antihypertensive effects, as well as the ability to regulate intestinal flora and promote fat metabolism. These properties render PACs highly promising for applications in the food, pharmaceutical, and cosmetic industries, garnering substantial interest from researchers globally. Additionally, PACs demonstrate significant nutritional benefits in animal husbandry. Dietary PACs can enhance animal growth, mitigate oxidative stress, decrease feeding expenses, and offer an environmentally friendly, antibiotic-free alternative. Therefore, PACs have great application potential in the field of pig production. This article reviews the basic properties, biological functions, and research status and application in pig production of PACs, aiming to provide theoretical guidance for the development of substitute antibiotic feed additives.

In Vitro Culture of Human Dermal Fibroblasts on Novel Electrospun Polylactic Acid Fiber Scaffolds Loaded with Encapsulated Polyepicatechin Physical Gels

Polyepicatechin (PEC) in a hydrogel has previously shown promise in enhancing physiological properties and scaffold preparation. However, it remains unclear whether PEC-based fibers can be applied in skin tissue engineering (STE). This study aimed to synthesize and characterize electrospun PEC physical gels and polylactic acid (PLA) scaffolds (PLAloadedPECsub) for potential use as constructs with human dermal fibroblasts (HDFs). PEC was produced through enzymatic polymerization, as confirmed by Fourier transform infrared (FTIR) spectroscopy. Scanning electron microscopy (SEM) demonstrated the feasibility of producing PLAloadedPECsub by electrospinning. The metabolic activity and viability of HDFs cocultured with the scaffolds indicate that PLAloadedPECsub is promising for the use of STE.

Procyanidin B2-3'-O-Gallate Derived from Grape Seed Polymeric Procyanidins via the Galloyl-Attached Nucleophilic Degradation as a Potential Hepatoprotective Agent

An effective method was developed for preparing galloylated procyanidins (GPCs) using galloyl-attached nucleophilic degradation. Under degradation conditions optimized through Box-Behnken design and single-factor experiments, two dimeric and three tetrameric GPCs were produced, with the yield of procyanidin B2-3'-O-gallate (B2-3'-G) reaching up to 232 mg/g (PPCs). The structure of B2-3'-G was identified by UV, FTIR, NMR, CD, MS, and phloroglucinolysis. Furthermore, the protective effect of B2-3'-G against alcohol-induced liver injury (ALI) was investigated. Compared with the parent compounds, B2-3'-G exhibited a stronger capacity for inhibiting ALI, attributed to its polymerization degree and galloyl group. Subsequent experiments revealed that the pretreatment of BRL-3A cells with B2-3'-G prior to ethanol improved ALI through activation of the Nrf2-HO-1/NQO1 pathway and initiation of enzymatic antioxidant systems. These findings suggest that GPC B2-3'-G is a potential hepatoprotective agent, which provides a new perspective for functional development of GPCs.

Evaluation of biological activity and prebiotic properties of proanthocyanidins with different degrees of polymerization through simulated digestion and in vitro fermentation by human fecal microbiota

The bioactive activity of proanthocyanidins (PAs) is closely associated with their degree of polymerization (DP), however, the effects of PAs with different DP on digestion and gut microbiota have remained unclear. To investigate this, we conducted in vitro simulated digestion and colonic fermentation studies on samples of PAs with different DP. The results showed that PAs was influenced by both protein precipitation and enzymolysis, resulting in a decrease in functional activity. PAs with a high DP were more sensitive to the gastrointestinal environment. The significant clustering trend in colonic fermentation verified the reliability of multivariate statistical techniques for screening samples with distinct functional differences. The gut microbiota analysis showed that oligomeric PAs had a stronger promoting effect on beneficial bacteria, while high polymeric PAs had a greater inhibitory effect on harmful bacteria. This study offers new insights into the biological activity and microbiological mechanisms of PAs with different DP.

Rapid screening and isolation of 5-lipoxygenase inhibitors in Inonotus obliquus and mechanism of action in the treatment of asthma

Accurate screening and targeted preparative isolation of active substances in natural medicines have long been two technical challenges in natural medicine research. This study outlines a new approach to improve the efficiency of natural product preparation, focusing on rapidly and accurately screening potential active ingredients in Inonotus obliquus as well as efficiently preparing 5-lipoxidase (5-LOX) inhibitors, to provide new ideas for the treatment of asthma with Inonotus obliquus. First, we used ultrafiltration (UF) mass spectrometry to screen for three potential inhibitors of 5-LOX in Inonotus obliquus. Subsequently, the inhibitory effect of the active ingredients screened in the UF assay on 5-LOX was verified using the molecular docking technique, and the potential role of the active compounds in Inonotus obliquus for the treatment of asthma was analyzed by network pharmacology. Finally, based on the above activity screening guidelines, we used semi-preparative liquid chromatography and consecutive high-speed countercurrent chromatography to isolate three high-purity 5-LOX inhibitors such as betulin, lanosterol, and quercetin. Obviously, through the above approach, we have seamlessly combined rapid discovery, screening, and centralized preparation of the active ingredient with molecular-level interactions between the active ingredient and the protease.

Novel l-Cysteine Incomplete Degradation Method for Preparation of Procyanidin B2-3'-O-Gallate and Exploration of its in Vitro Anti-inflammatory Activity and in Vivo Tissue Distribution

In this study, an effective method for preparation of bioactive galloylated procyanidin B2-3'-O-gallate (B2-3'-G) was first developed by incomplete depolymerization of grape seed polymeric procyanidins (PPCs) using l-cysteine (Cys) in the presence of citric acid. The structure-activity relationship of B2-3'-G was further evaluated in vitro through establishing lipopolysaccharide (LPS)-induced inflammation in RAW264.7 cells. The results suggested that the better protective effects of B2-3'-G against inflammation were attributed to its polymerization degree and the introduction of the galloyl group, compared to its four corresponding structural units. In vivo experiments demonstrated that the B2-3'-G prototype was distributed in plasma, small intestine, liver, lung, and brain. Remarkably, B2-3'-G was able to penetrate the blood-brain barrier and appeared to play an important role in improving brain health. Furthermore, a total of 18 metabolites were identified in tissues. Potential metabolic pathways, including reduction, methylation, hydration, desaturation, glucuronide conjugation, and sulfation, were suggested.

Exploring separation patterns and mechanisms of proanthocyanidins in grape seeds and pomace with diverse molecular weights, compositions, and structures

The function of proanthocyanidins (PAs) relies on their structure and requires high-purity PAs. Though Sephadex LH-20 gel permeation chromatography (GPC) is expected to separate PAs based on structure, its usage rules and mechanisms remain unclear. This study delves into the PAs separation patterns on Sephadex LH-20, first confirming the purification mechanisms of PAs with various mean degrees of polymerization (DP) using the adsorption kinetic model. The study found that an increase in the molecular weight or mean DP of PAs results in decreased polarity, reduced hydrogen bonding actions, and intensified hydrophobic effect, causing delayed extraction of PAs on Sephadex LH-20, with galloylated PA as an exception, which was extracted first despite its high DP. Additionally, the principles for separating specific composition, such as monomers, dimers, etc., were evaluated. The study sheds light on enhancing the purification efficiency of PAs, thus advancing the precise separation technology of diverse proanthocyanidins.

Application of one-step inner-recycling counter-current chromatography for the preparative separation and purification of chemical constituents from the rhizome of Bergenia ciliate (haw.) Sternb

Bergenia ciliata (haw.) Sternb, the renowned pharmaceutical plant in Jammu and Kashmir of Pakistan, is widely applied in treating different illnesses including diabetes, diarrhea, and vomiting. This work employed an efficient one-step inner-recycling counter-current chromatography for preparative separating and purifying compounds with similar partition coefficients from the rhizome of Bergenia ciliate (haw.). Five compounds, including quercetin rhamnodiglucoside (1), quercetin-3-O-rutinoside (2), bergenine (3), kaempferol (4), and palmatic acid (5), were successfully separated using the optimized biphasic solvent system that contained ter-butylmetylether/n-butanol/acetonitrile/water (2:2:1:5, v/v) with the purities over 98%. Mass spectrometry and nuclear magnetic resonance were conducted for structural identification. As a result, our proposed strategy might be applied in separating compounds with similar partition coefficients, which was advantageous with regard to the less solvent and time consumption, and the increased number of theoretical plates.

Isolation and purification of high polar glycosides from aerial parts of Gynostemma pentaphyllum (Thunb.) Makino by linear gradient counter-current chromatography coupled with inner-recycling mode

Gynostemma pentaphyllum (Thunb.) Makino represents the popular health food and supplemental product with broad pharmacological activities. The highly polar glycosides, including flavonoids and saponins, are major effective active components that contain diverse sugar positions and quantities, which result in diverse chemical polarities, making it challenging to separate and isolate these components. The present work described the rapid and efficient linear gradient counter-current chromatography to preparatively separate glycosides from aboveground parts of G. pentaphyllum. Besides, the ethyl acetate and n-butanol binary mobile phases were achieved through adjusting associated proportions. Six glycosides, including quercetin-3-O-neohesperidoside (1), kaempferol-3-O-robinobioside (2), kaempferol-3-O-neohesperidoside (3), gypenoside LVI (4), ginsenoside Rb3 (5), and gypenoside XLVI (6), were isolated at the purities greater than 98%. Moreover, electrospray ionization mass spectrometry and nuclear magnetic resonance tandem mass spectrometry were conducted for structural identification. According to our findings, the established linear gradient counter-current chromatography was an efficient approach to separate the highly polar glycosides from aboveground parts of G. pentaphyllum. Our proposed strategy can be used to separate active compounds from other complex natural products.

Procyanidin B2: A promising multi-functional food-derived pigment for human diseases

Natural edible pigments play a paramount part in the food industry. Procyanidin B2 (PB2), one of the most representative naturally occurring edible pigments, is usually isolated from the seeds, fruits, and leaves of lots of common plants, such as grapes, Hawthorn, black soybean, as well as blueberry, and functions as a food additive in daily life. Notably, PB2 has numerous bioactivities and possesses the potential to treat/prevent a wide range of human diseases, such as diabetes mellitus, diabetic complications, atherosclerosis, and non-alcoholic fatty liver disease, and the underlying mechanisms were partially elucidated, including mediating signaling pathways like NF-κB, MAPK, PI3K/Akt, apoptotic axis, and Nrf-2/HO-1. This paper presents a review of the natural sources, bioactivities, and the therapeutic/preventive potential of PB2 and the possible mechanisms, with the aim of promoting the development of PB2 as a functional food and providing references for its clinical application in the treatment of diseases.

UPLC-Q-TOF-MS and NMR identification of structurally different A-type procyanidins from peanut skin and their inhibitory effect on acrylamide

BACKGROUND

Flavan-3-ol polyphenols have been shown to have great advantages in inhibiting acrylamide formation. However, flavan-3-ol polyphenols have structures that vary significantly, and existing research has been focused mainly on the effects of B-type procyanidins and structural units of procyanidins. This study aims to separate structurally different A-type procyanidins from peanut skin and compare their inhibitory effects on acrylamide in an asparagine-glucose simulation system.

RESULTS

Five compounds were separated and identified from peanut skin, including epicatechin-(2β → O → 7, 4β → 8)-ent-epicatechin, epicatechin-(2β → O → 7, 4β → 8)-epicatechin, epicatechin-(2β → O → 7, 4β → 8)-epicatechin-(4β → 6)-catechin, epicatechin-(2β → O → 7, 4β → 8)-epicatechin-(4β → 8)-catechin, and epicatechin-(4β → 6)-epicatechin-(4β → 8, 2β → O → 7)-catechin. All the procyanidins could reduce the acrylamide content within a certain range of concentrations. The highest inhibition rates followed the order of compound 5 (A-type trimer) > compound 1 (A-type dimer) > compound 2 (A-type dimer) > compound 3 (A-type trimer) > compound 4 (A-type trimer). Comparison analysis showed that structurally different A-type procyanidins have various inhibitory effects on acrylamide production, which may be related to their spatial configuration and bond connection mode.

CONCLUSION

Overall, our findings help us to gain a better understanding of the relationship between the structure of procyanidins and their inhibitory effects on acrylamide, particularly the inhibitory effect of A-type. There are potential practical implications if people use A-type procyanidins as acrylamide inhibitors in hot processed foods in the future. © 2022 Society of Chemical Industry.

Integrated LC-MS/MS method and network pharmacology for exploring the characterization and mechanism of neuroprotective effect of Vitis amurensis Rupr. wine polyphenol

Polyphenols are the main active components in Vitis amurensis Rupr. wine, which show good protective effects on the nervous system, but their compositions in Vitis amurensis Rupr. wine and the molecular mechanism underlying their neuroprotection remains unclear. The purpose of this study is to investigate the potential mechanism of the neuroprotective effect of Vitis amurensis Rupr. wine polyphenols on the basis of the specific composition of polyphenols in Vitis amurensis Rupr. wine. In this study, 40 phenolic compounds which include 15 anthocyanins, 10 flavonoids, 10 phenolic acids, 3 proanthocyanidins and 2 resveratrols were identified by UPLC Q-Exactive Orbitrap MS. Furthermore, An UPLC-QqQ/MS method was established to simultaneously determine the phenolic compounds in Vitis amurensis Rupr. Wine, and analyze the content differences of phenolic compounds between Vitis amurensis Rupr. and Vitis vinifera wine. Finally, network pharmacology was employed for the first time to predict the possible pharmacological mechanisms of Vitis amurensis wine polyphenols against nervous damage. Multivariate network analysis indicated that quercetin, (-)-epigallocatechin and various anthocyanins were found as prominent compounds for the treatment of nervous system diseases. Vitis amurensis Rupr. wine polyphenols mainly acted on these key targets, including AKT1, EGFR, ESR1, and SRC, and further regulate the PI3K-AKT and Rap1 signaling pathway for treating nervous system diseases. Our findings suggested that polyphenols in Vitis amurensis Rupr. wine possess neuroprotective effect through multicomponent, multitarget, and multichannel. PRACTICAL APPLICATIONS: Studies have revealed that Vitis amurensis Rupr. has higher levels of phenolic compounds than Vitis vinifera wine. However, due to the few and limited study of Vitis amurensis Rupr., their compositions in Vitis amurensis Rupr. wine and the molecular mechanism underlying their neuroprotection remains unclear. This research uses a holistic network pharmacology strategy to investigate the potential targets and pharmacological mechanisms of Vitis amurensis Rupr. wine polyphenols against nervous damage. To some things up, The finding elucidates the relationships between signaling pathways, targets, and compounds in Vitis amurensis Rupr. wine polyphenols, which may provide guidance and foundations for further application of medicinal food.

Protective effect of grape seed extract against chronic physical stress-induced zona fasciculata injury in male rats: Functional, immunohistochemical and electron microscopic study

In the present study, we investigated the antioxidant effect of grape seed extract (GSE) against chronic immobilization stress-induced zona fasciculata injury in Wistar male rats. Thirty male rats were divided into three groups: Non-stress group: rats were not subjected to stress protocol and received distilled water orally for 30 days. Stress group: rats received distilled water orally for 15 consecutive days before the induction of chronic immobilization stress experiment (repeated stress for 15 consecutive days), distilled water was continued along with the constant stress experiment. GSE-stress group: rats treated with oral GSE (300 mg/kg), administered orally for 15 consecutive days before the induction of chronic immobilization stress experiment (repeated stress for 15 consecutive days), GSE was continued along with the stress exposure. Chronic stress was induced by placing each animal in a restrainer for 2 h daily for 15 consecutive days in both Stress and GSE-stress groups. The serum corticosterone and adrenal cortex malondialdehyde (MDA) levels were measured as indices of stress. Immunohistochemistry of the inducible nitric oxide synthase (iNOS) as a nitrosative stress marker beside the adrenal cortex's ultrastructure, particularly zona fasciculata, was assessed. Chronic restraint stress significantly elevated the serum corticosterone and adrenal cortex MDA levels, while oral administration of GSE reduced the serum corticosterone level, adrenal cortex MDA levels, and iNOS immunoreactivity in zona fasciculata. Besides, adrenocortical ultrastructure significantly improved. These results suggested that GSE enhanced the antioxidant defense against reactive oxygen species produced under chronic stress conditions, protecting the adrenal cortex.

One-Step Preparative Separation of Fucoxanthin from Three Edible Brown Algae by Elution-Extrusion Countercurrent Chromatography

A method for batch preparation of fucoxanthin from brown algae was established, which possessed the advantages of high yield and high purity. The ultrasonic-assisted extraction method was used to obtain a crude extract from Sargassum fusiforme as the separation sample. Then the crude extract was separated by elution-extrusion countercurrent chromatography. The optimum preparation conditions of fucoxanthin were determined as follows: n-hexane-ethanol-water (20:9:11, v:v:v) as a two-phase solvent system, the mobile phase flow rate was 5 mL min-1, the revolution speed was 800 r min-1, the loading capacity was 60 mg 10 mL-1 and the temperature was 25 °C. By this method, 12.8 mg fucoxanthin with a purity of 94.72% was obtained from the crude extract of Sargassum fusiforme. In addition, when the loading capacity was 50 mg 10 mL-1, the purity of fucoxanthin reached 96.01%. Two types of by-products, chlorophyll and pheophytin, could also be obtained during the process of separation. This optimal method was further applied to separate fucoxanthin from Laminaria japonica and Undaria pinnatifida, and 6.0 mg and 9.7 mg fucoxanthin with a purity of 96.24% and 92.62% were acquired, respectively. Therefore, it was demonstrated that the preparation method of fucoxanthin established in this study had an applicability to brown algae, which improved the utilization value of raw materials.

Rapid fingerprinting of extractable and non-extractable polyphenols from tropical fruit peels using direct analysis in real time coupled to orbitrap mass spectrometry

A simple and rapid direct analysis in real-time coupled to high-resolution mass spectrometry (DART-HRMS) methodology was developed to generate the extractable and non-extractable polyphenols (NEPs) fingerprint for four different passion fruits, G. mangostana, and A. squamosa peels as case-study to investigate the influence of alkaline hydrolysis and enzymatic-assisted extraction (EAE) on the recovery of NEPs. The extraction residue obtained after these treatments was also analyzed by DART-HRMS. Data compiled from DART-HRMS mass spectra were processed with principal component analysis to discriminate among the different treatments. EAE with Depol enzyme enabled to obtain NEPs with the highest signal intensity in DART-HRMS analysis from all peels except for P. edulis and A. squamosa peels. In these two cases, NEPs were better extracted by EAE with Promod enzyme and alkaline hydrolysis. Results showed that the applied treatments were efficient to extract NEPs since their signal intensities in the extraction residues were very low compared with their extracts.

Proanthocyanidin A1 promotes the production of platelets to ameliorate chemotherapy-induced thrombocytopenia through activating JAK2/STAT3 pathway

BACKGROUND

Chemotherapy-induced thrombocytopenia (CIT) is a severe adverse drug reaction, and the main reason for CIT is the destruction of megakaryocytes (MKs, precursor cells of platelet) in bone marrow by chemotherapy. Peanut skin, the seed coat of Arachis hypogaea L., is a traditional Chinese medicine commonly used to treat thrombocytopenia. However, its active compounds and the mechanisms remain unclear.

PURPOSE

This study aims to clarify the active compounds of peanut skin to exhibit thrombogenic effects against CIT and their underlying mechanisms in vitro and in vivo.

STUDY DESIGN

The bioassay-guided isolation based on the proliferation of MKs was used to explore the possible platelet-enhancing ingredients in peanut skin. HSCCC technique coupled with preparative HPLC was used to separate the active compounds. Dami cells and carboplatin-treated mice model were used to evaluate the thrombogenic effects of PS-1. Network pharmacology, molecular docking, dynamics simulation studies, kinase activity, surface plasmon resonance (SPR), cellular thermal shift assay (CETSA), isothermal dose-response fingerprint (ITDRF_CETSA) and western blot analysis were performed to investigate the mechanisms of PS-1.

RESULTS

Proanthocyanidin A1 (PS-1) and its stereoisomers (PS-2-4) were demonstrated to promote the proliferation of MKs (Dami cells), especially PS-1 (EC₅₀ = 8.58 μM). Further studies demonstrated that PS-1 could induce the differentiation of Dami cells in dose/time-dependent manner. Biological target analysis showed that PS-1 directly bound to JAK2 (KD = 2.06 μM) to exert potent activating effect (EC₅₀ = 0.66 μM). Oral administration of PS-1 (25 or 50 mg/kg) significantly improved CIT, but this effect was confirmed to be inhibited by JAK2 inhibitor AG490, indicating that PS-1 exerted its efficacy through JAK2 in vivo.

CONCLUSION

Proanthocyanins (PS-1-4) derived from peanut skin were first clarified as platelet-enhancing ingredients to improve CIT. The underlying mechanism of PS-1 was proved to promote the proliferation and differentiation of MKs via JAK2/STAT3 pathway both in vitro and in vivo.

The condensed tannin chemistry and astringency properties of fifteen Vitis davidii Foex grapes and wines

This study sought to determine the effects of variety on the astringency and chemistry of condensed tannins of spine grapes and wines. Fifteen varieties of red spine grape (Vitis davidii Foex) were used. Condensed tannin content, composition, and wine astringency were determined. The condensed tannin profiles were assessed by high-performance liquid chromatography coupled with diode array detector (HPLC-DAD). The condensed tannin content highly depended on the variety ranging from 0.30 mg/g to 7.80 mg/g (in skins), from 3.12 mg/g to 8.82 mg/g (in seeds), and from 62.60 mg/L to 225.90 mg/L (in wines). There were significant differences in proportions of certain constitutive subunits (as mole%) and mean degree of polymerization (mDp) among the varieties. Correlation analysis revealed that condensed tannin concentration and composition had a significant effect on the sensory evaluation and quantitative analysis of astringency. A positive correlation between mDp and astringency was also observed. The present results expand knowledge of the characterization of spine grape and wine condensed tannin chemistry and astringency.

Isolation and purification of flavonoids from Euonymus alatus by high-speed countercurrent chromatography and neuroprotective effect of rhamnazin-3-O-rutinoside in vitro

The flavonoids from Euonymus alatus exhibit many biological activities including significant antioxidant, anti-inflammatory, anti-cancer. In this work, a high-speed countercurrent chromatography method for the isolation and purification of flavonoids from crude extracts of Euonymus alatus was established. The effects of several solvent systems on the separation efficiency of target compounds in the extract of Euonymus alatus were studied. The solvent system composed of n-hexane-ethyl acetate-methanol-water at a volume ratio of (3:5:3:5, v/v) was chosen, in which the lower phase was used as the mobile phase at the rotation speed of 800 rpm and flow rate of 2.0 mL/min. The three flavonoids were obtained and identified as patuletin-3-O-rutinoside, rhamnazin-3-O-rutinoside, and dehydrodicatechin A by mass spectroscopy and nuclear magnetic resonance, and the quantities of patuletin-3-O-rutinoside, rhamnazin-3-O-rutinoside, and dehydrodicatechin A were 2.2, 9.7, and 1.8 mg, respectively. The results indicated that high-speed countercurrent chromatography was a simple and efficient method for the isolation and purification of flavonoids from the crude extracts of Euonymus alatus. The cellular antioxidant activity experimental result indicated that rhamnazin-3-O-rutinoside could alleviate H₂ O₂ -induced oxidative stress.

Novel perspectives of environmental proteomics

The connection among genome expression, proteome alteration, metabolism regulation and phenotype change under environmental stresses is very vague. It is a tough task for the traditional research approaches to reveal the related scientific mechanisms of the above connection at molecular and systematic levels. Proteomics approach is an insightful tool for revealing the biological functions, metabolic networks and functional protein interaction networks of cells and organisms under stresses at the systematic level. The purpose of this review is to provide an insightful guideline on how to set up a proteomic investigation for revealing biomolecule mechanisms, protein biomarkers and metabolism networks related to stress response, pollutant recognition, transport and biodegradation, and providing an insightful high-throughput approach for screening functional enzymes and effective microbes based on bioinformatics and functional verification method. Furthermore, the toxicity evaluation of pollutants and byproducts by proteomics approaches provides a scientific insight for early diagnosis of ecological risk and determination of the effectiveness of pollutant treatment techniques.

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.

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

The fruits of Sorbus pohuashanensis Hedl. (S. pohuashanensis) are rich in polyphenols with many beneficial effects such as anti-inflammatory, anti-tussive, anti-asthmatic and anti-cancer. In this study, five polyphenols, including three phenolic acids and two flavonoids, were successfully prepared from the fruits of S. pohuashanensis by high-speed counter-current chromatography (HSCCC) using different solvent systems for the first time. Ethyl acetate-n-butanol-water (3.5:1.5:5, v/v) was screened as the two-phase system to separate neochlorogenic acid (1), chlorogenic acid (2), quercetin 3-O-(6″-α-L-rhamnopyranosyl-4'″-α-L-rhamnopyranosyl)-β-D-glucopyranoside (3) and rutin (5). N-hexane-ethyl acetate-methanol-water (1:3:1:3.5, v/v) was first utilized to isolate 3,5-O-dicaffeoylquinic acid (4). The purities of all these compounds were above 95%. In addition, their chemical structures were identified by mass spectrometer (MS), nuclear magnetic resonance (NMR) or the standards. These results indicated that HSCCC was an effective method to separate polyphenols compounds from the fruits of S. pohuashanensis.

Development of MALDI MS peptide array for thrombin inhibitor screening

The development of in situ methods for the analysis and visualization of enzyme activity is of paramount importance in drug discovery, research, and development. In this work, the functionalized and array patterned indium tin oxide (ITO) glass slides were fabricated by non-covalent immobilization of amphipathic phospholipid-tagged peptides encompassing the thrombin cleavage site on steric acid-modified ITO slides. The fabricated peptide arrays provide 60 spots per slide, and are compatible with matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) measurement, free matrix peak interference, and tolerance to repeated aqueous washing. The peptide arrays were used for the investigation of thrombin activity and screening for its potential inhibitors. The thrombin activity and its Michaelis-Menten constant (K_m) for immobilized peptide substrate was determined using developed MALDI MS peptide array. To investigate the applicability and effectiveness of peptide arrays, the anti-thrombin activity of grape seed proanthocyanidins with different degrees of polymerization (DP) was monitored and visualized. MALDI MS imaging results showed that the fractions of proanthocyanidins with the mean DP of 4.61-6.82 had good thrombin inhibitory activity and their half-maximal inhibitory concentration (IC₅₀) were below 10 μg/mL. Therefore, the developed peptide array is a reliable platform for the discovery of natural thrombin inhibitors.

Proanthocyanidins Should Be a Candidate in the Treatment of Cancer, Cardiovascular Diseases and Lipid Metabolic Disorder

The conventional view of using medicines as routine treatment of an intractable disease is being challenged in the face of extensive and growing evidence that flavonoids in foods, especially proanthocyanidins (PAs), can participate in tackling fatal diseases like cancer, cardiovascular and lipid metabolic diseases, both as a precautionary measure or as a dietary treatment. Although medical treatment with medicines will remain necessary in some cases, at least in the short term, PAs’ function as antioxidant, anti-inflammatory drugs, signal pathway regulators remain critical in many diseases. This review article demonstrates the physical and biological properties of PAs, summarizes the health benefits of PAs found by researchers previously, and shows the possibility and importance of being a dietary treatment substance.

Characterization of Antibacterial Proanthocyanidins of Dalbergia monetaria, an Amazonian Medicinal Plant, by UHPLC-HRMS/MS

Dalbergia monetaria is an Amazonian plant whose bark is widely used to treat urinary tract infections. This paper describes a bio-guided study of ethanolic extracts from the bark and leaves of D. monetaria, in a search for metabolites active against human pathogenic bacteria. In vitro assays were performed against 10 bacterial strains, highlighting methicillin-sensitive Staphylococcus aureus and methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa. Fractioning of the extracts was performed using instrumental and classical techniques, and samples were characterized by UHPLC-HRMS/MS. Ethyl acetate fractions from bark and leaves showed similar antibacterial activities. EAFB is enriched in isoflavone C-glucosides and EAFL enriched in proanthocyanidins. Subfractions from EAFL presented higher activity and showed a complex profile of proanthocyanidins constructed by (epi)-cassiaflavan and (epi)-catechin units, including dimers, trimers and tetramers. The fragmentation pattern emphasized the neutral loss of cassiaflavan units by quinone-methide fission. Fraction SL7-6, constituted by (ent)-cassiaflavan-(ent)-cassiaflavan-(epi)-catechin isomers, showed the lowest MIC against the S. aureus and P. aeruginosa with values corresponding to 64 and 32 µg/mL, respectively. Cassiaflavan-proanthocyanidins have not been found previously in another botanical genus, except in Cassia, and the traditional medicinal use of D. monetaria might be related to the antibacterial activity of proanthocyanidins characterized in the species.

Purification of Sesquiterpenes from Saussurea Lappa Roots by High Speed Counter Current Chromatography

Sesquiterpenes lactones including costunolide and dehydrocostus lactone, were isolated from Saussurea lappa roots, which had exhibited a wide range of biological activities such as anti-cancer, anti-inflammatory, antiulcer, and immunomodulatory activities. High-speed counter-current chromatography (HSCCC) was applied for the rapid preparative isolation of sesquiterpenes lactones from Saussurea lappa roots. A solvent optimization method for HSCCC was presented, i.e. the separation factors of compounds after the partition coefficient (K) of solvent system should be investigated. Using this method, 150 mg of costunolide, 140 mg of dehydrocostus and 15 mg of 10-methoxy-artemisinic acid with purities of 95%, 98%, and 98% were obtained within 150 min. The structures of three compounds were identified by mass spectrum (MS) and nuclear magnetic resonance (NMR) spectroscopy. These results offered an efficient strategy for separation of potentially health-relevant phytochemicals from Saussurea lappa roots.

Evaluation of an Integrated Ultrafiltration/Solid Phase Extraction Process for Purification of Oligomeric Grape Seed Procyanidins

The effectiveness of a preparative integrated ultrafiltration/solid-phase extraction (UF/SPE) process for purification of oligomeric procyanidins (OPCs) from a crude grape seed extract (GSE) was studied for the first time. The separation of OPCs from polymeric procyanidins (PPCs) by UF was very efficient. The membrane showed an acceptable filtration flux of 6 to 3.5 L/h·m² at 0.5 bar of transmembrane pressure and 95% recovery of its water flux after chemical cleaning. The process was scalable to a pilot scale. The separation of very polar and ionic species from OPCs by SPE (XAD7HP and XAD16 resins) was also very good, but both adsorbents lost their retention capacities quickly, due probably to irreversible retention of OPCs/PPCs. Even though the global purification of OPCs by the integrated UF/SPE process allowed the recovery of 24.2 g of highly purified OPCs (83% purity) from 14.4 L of crude grape seed extract, the use of these adsorbents for further purification of the OPCs was very limited.

Preparative Separation of Procyanidins from Cocoa Polyphenolic Extract: Comparative Study of Different Fractionation Techniques

To provide further insight into the antioxidant potential of procyanidins (PCs) from cocoa beans, PC extract was fractionated by several methodologies, including solid phase extraction, Sephadex LH-20 gel permeation, and preparative HPLC using C18 and diol stationary phases. All the isolated fractions were analyzed by UHPLC-QTOF-MS to determine their relative composition. According to our results, classical techniques allowed good separation of alkaloids, catechins, dimers, and trimers, but were inefficient for oligomeric PCs. Preparative C18-HPLC method allowed the attainment of high relative composition of fractions enriched with alkaloids, catechins, and PCs with degree of polymerization (DP) < 4. However, the best results were obtained by preparative diol-HPLC, providing a separation according to the increasing DP. According to the mass spectrometry fragmentation pattern, the nine isolated fractions (Fractions II–X) consisted of exclusively individual PCs and their corresponding isomers (same DP). In summary, an efficient, robust, and fast method using a preparative diol column for the isolation of PCs is proposed. Regarding DPPH^• and ABTS^•+ scavenging activity, it increases according to the DP; therefore, the highest activity was for cocoa extract > PCs > monomers. Thereby, cocoa procyanidins might be of interest to be used as alternative antioxidants.

New perspectives on the biosynthesis, transportation, astringency perception and detection methods of grape proanthocyanidins

Proanthocyanidins (PAs) are important secondary metabolites crucial for the quality of grape berry and wine. Despite important advances in our understanding of the structural and regulatory genes involved in the PAs biosynthesis pathway, our knowledge about the details of biosynthetic and regulatory networks, especially the mechanism of polymerization and transportation remains limited. We provided an overview of the latest discoveries related to the mechanisms of grape PAs structure, astringency properties, detection methods, biosynthesis and transportation. We also summarized the environmental influencing factors of PAs synthesis in grape. Future trends were discussed.

The applicability of high-speed counter current chromatography to the separation of natural antioxidants

Antioxidants play an essential role in human health, as they have been found to be capable of lowering the incidence of many diseases, such as cancer and angiocardiopathy. Currently, more attention is paid to natural antioxidants because of the possible insecurity of synthetic antioxidants. Thus, the development of efficient techniques or methods to separate antioxidants from natural sources is requested urgently. High-speed counter current chromatography (HSCCC) is a unique support-free liquid-liquid chromatographic technique and has been widely applied in the field of separation of natural products. In this review, we summarize and analyze the related researches on the application of HSCCC in the separation of various natural antioxidants so far. The purpose of the article is to provide a certain theoretical support for the separation of natural antioxidants by HSCCC, and to make full use of advantages of HSCCC in the separation of bioactive components. In particular, some key problems associated with the separation strategies, the structural categories of natural antioxidants, solvent system choices, and the application of different elution modes in HSCCC separation, are summarized and commented. We expect that the content reviewed can offer more evidence for the development of the field of natural antioxidants separation, so as to achieve large-scale preparation of natural antioxidants.

Isolation and purification of alkaloids from the fruits of Macleaya cordata by ionic-liquid-modified high-speed counter-current chromatography

Macleaya cordata (Willd) R. Br. is a medicinal plant. The most important bioactive compounds of M. cordata are alkaloids that have many biological activities including antifungal, anti-inflammatory, and antitumor. In this study, an ionic-liquid-modified high-speed counter-current chromatography method was established to obtain alkaloids from the fruits of M. cordata. The conditions of ionic-liquid-modified high-speed counter-current chromatography, including solvent systems, the content of ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate [C₄ mim][BF₄ ]), and the posttreatment of the ionic liquid, were investigated. Five alkaloids protopine, allocryptopine, sanguinarine, 8-O-demethylchelerythrine, and chelerythrine were separated from the extract of the fruits using a high speed counter-current chromatography with two-phase solvent system composed of dichloromethane/methanol/0.3 mol/L hydrochloric acid aqueous solution/[C₄ mim][BF₄ ] (4:2:2:0.015, v/v). Their purities were 96.33, 95.56, 97.94, 96.22, and 97.90%, respectively. The results indicated that a small amount of ionic liquids as modifier of the two-phase solvent system could shorten the separation time and improve the separation efficiency of the alkaloids from the fruits. The ionic-liquid-modified high-speed counter-current chromatography would provide a feasible way for highly effective separation of alkaloids from natural products.

Phenols and Melanoidins as Natural Antioxidants in Beer. Structure, Reactivity and Antioxidant Activity

Beer is one of the most consumed drinks around the world, containing a variety of compounds that offer both appreciated sensorial characteristics and health advantages. Important healthy compounds in beer are those with antioxidant properties that attenuate the content of free radicals produced as by-products in the human metabolism, exerting an appreciable effect against cancers or cardiovascular diseases. This work details a study of antioxidant compounds present in beer, focusing on the two main groups: phenols (including polyphenolic forms) and melanoidins, formed specifically during brewing as Maillard products. The fundaments of the most important methods to evaluate beer antioxidant activity, the main antioxidant compounds present in beer-especially those with healthy properties-and the new trends to increase beer antioxidant activity are also discussed.

Novel Catechin-Tiopronin Conjugates Derived from Grape Seed Proanthocyanidin Degradation: Process Optimization, High-Speed Counter-Current Chromatography Preparation, as Well as Antibacterial Activity

Tiopronin, as a novel thiol-containing nucleophile, was introduced for depolymerizing polymeric proanthocyanidins from grape seed into catechins and three new proanthocyanidin-tiopronin degradation products: (+)-catechin-4β-S-tiopronin methyl ester (CT), (-)-epicatechin-4β-S-tiopronin methyl ester (ECT), and (-)-epicatechin gallate-4β-S-tiopronin methyl ester (ECGT). A Box-Behnken design was employed to optimize degradation conditions based on single-factor experiments to obtain target products. Each of the new degradation compounds was isolated by the high-speed counter-current chromatography combined with semipreparative high performance liquid chromatography in large amounts, and then, their structures were identified by ¹H NMR, ¹³C NMR, 2D-NMR, as well as mass spectrometry analysis. The absolute configurations were further confirmed by comparison between the calculated electronic circular dichroism and experimental spectra. Further evaluation of antibacterial activities of these compounds showed that CT and ECT possessed more inhibiting capacity against Staphylococcus aureus and Escherichia coli than parent compound catechin and epicatechin. However, ECGT has no bacteriostatic capacity against these two bacteria.

Development of a method to screen and isolate bioactive constituents from Stellera chamaejasme by ultrafiltration and liquid chromatography combined with semi-preparative high-performance liquid chromatography and high-speed counter current chromatography

A simple and efficient method based on ultrafiltration with liquid chromatography and mass spectrometry was used for the rapid screening and identification of ligands in the extracts of Stellera chamaejasme. The bound ligands, i.e. daphnoretin, isopimpinellin, chamaechromone, neochamaejasmin A, and chamaejasmine (purity of 96.8, 90.75, 91.41, 93.98, and 98.91%, respectively), were separated by semi-preparative high-performance liquid chromatography combined with high-speed counter-current chromatography. To the best of our knowledge, this is the first study to report the detection of potent lipoxidase and lactate dehydrogenase inhibitors in Stellera chamaejasme extracts. The results demonstrate that our method of ultrafiltration with liquid chromatography and mass spectrometry combined with mixed chromatography can be used to screen and confirm the bioactivity of all isolated compounds. This method also eliminates the need for separation of inactive compounds, thereby improving efficiency when studying bioactive substances. For some complex mixtures, neither semi-preparative high-performance liquid chromatography nor high-speed counter-current chromatography can purify all the target active compounds with high purity in a one-step separation. The combination of the two methods allow for efficient purification of target bioactive compounds with different polarities and physicochemical properties based on their complementary properties.

Optimizing Nucleophilic Depolymerization of Proanthocyanidins in Grape Seeds to Dimeric Proanthocyanidin B1 or B2

Depolymerization of polymeric proanthocyanidins (PPCs) in grape seeds into oligomeric proanthocyanidins (OPCs), especially the dimers, has important academic significance and practical value. Reaction conditions including nucleophilic reagent/PPC mass ratio, HCl concentration, reaction time, and temperature were systematically optimized by central composite design to maximize the yield of the dimeric product B2 or B1. The yield of B2 reached 3.35 mg mL^-1 under the conditions of (-)-epicatechin/PPC mass ratio 2.8, HCl concentration 0.06 mol, reaction time 16 min and temperature 36 °C, and that of B1 reached 3.64 mg mL^-1 under the conditions of (+)-catechin/PPC mass ratio 2.8, HCl concentration 0.07 mol, reaction time 17 min, and temperature 34 °C. Overall, this study has provided theoretical guidance and a practical approach to improvethe reaction process and economic value of proanthocyanidins in grape seed proanthocyanidin extract.

Extraction of Proanthocyanidins from Chinese Wild Rice (Zizania latifolia) and Analyses of Structural Composition and Potential Bioactivities of Different Fractions

Due to the importance of proanthocyanidin bioactivity and its relationship with chemical structure, ultrasound-assisted extraction and purification schemes were proposed to evaluate the proanthocyanidin content and analyze the structural composition and potential bioactivities of different proanthocyanidin fractions from Chinese wild rice (Zizanialatifolia). Following an optimized extraction procedure, the crude wild rice proanthocyanidins (WRPs) were purified using n-butanol extraction, chromatography on macroporous resins, and further fractionation on Sephadex LH-20 to yield six specific fractions (WRPs-1–WRPs-6) containing proanthocyanidin levels exceeding 524.19 ± 3.56 mg/g extract. Structurally, (+)-catechin, (−)-epicatechin, and (−)-epigallocatechin were present as both terminal and extension units, and (−)-epicatechin was the major extension unit, in each fraction. This is the first preparation of WRP fractions with a different mean degree of polymerization (mDP), ranging from 2.66 ± 0.04 to 10.30 ± 0.46. A comparison of the bioactivities of these fractions revealed that fractions WRPs-1−WRPs-5 had significant DPPH radical scavenging activities, whereas fraction WRPs-6 with a high mDP showed better α-glucosidase and pancreatic lipase inhibitory effects. These findings should help define possible applications of WRPs to functional foods or nutraceuticals.

Screening and isolation of cyclooxygenase-2 inhibitors from Trifolium pratense L. via ultrafiltration, enzyme-immobilized magnetic beads, semi-preparative high-performance liquid chromatography and high-speed counter-current chromatography

Nonsteroidal anti-inflammatory drugs reportedly reduce the risk of developing cancer. One mechanism by which they reduce carcinogenesis involves the inhibition of the activity of cyclooxygenase-2, an enzyme that is overexpressed in various cancer tissues. Its overexpression increases cell proliferation and inhibits apoptosis. However, selected cyclooxygenase-2 inhibitors can also act through cyclooxygenase-independent mechanisms. In this study, using ultrafiltration, enzyme-immobilized magnetic beads, high-performance liquid chromatography, and electrospray-ionization mass spectrometry, several isoflavonoids in Trifolium pratense L. extracts were screened and identified. Semi-preparative high-performance liquid chromatography and high-speed counter-current chromatography were then applied to separate the active constituents. Using these methods, seven major compounds were identified in Trifolium pratense L. As cyclooxygenase-2 inhibitors: rothindin, ononin, daidzein, trifoside, pseudobaptigenin, formononetin, and biochanin A, which were then isolated with >92% purity. This is the first report of the presence of potent cyclooxygenase-2 inhibitors in Trifolium pratense L. extracts. The results of this study demonstrate that the systematic isolation of bioactive components from Trifolium pratense L., by using ultrafiltration, enzyme-immobilized magnetic beads, semi-preparative high-performance liquid chromatography, and high-speed counter-current chromatography, represents a feasible and efficient technique that could be extended for the identification and isolation of other enzyme inhibitors.

Recovery of Oligomeric Proanthocyanidins and Other Phenolic Compounds with Established Bioactivity from Grape Seed By-Products

Grape seeds are a copious part of the grape pomace produced by wine and juice industry and they represent an interesting source of phenolic compounds. Proanthocyanidins (PAs) are the main class of grape seed phenols and are important dietary supplements for their well-known beneficial properties. In this study enriched extracts obtained from Chardonnay and Pignoletto grape seeds were characterized for their proanthocyanidins and other minor phenolic compounds content and composition. Seed PAs were fractionated using Sephadex LH-20, using different ethanol aqueous solutions as mobile phase and analysed by normal phase HPLC-FLD-ESI-MS. Monomers, oligomers up to dodecamers and polymers were recorded in all samples. For both cultivars, the extracts showed a high content in PAs. The determination of other phenolic compounds was carried out using a HPLC-QqQ-ESI-MS and Chardonnay samples reported a greater content compared to Pignoletto samples. Contrary to PAs fraction, extracts obtained with ethanol/water 50/50 (v/v) presented a significant higher phenolic content than the others.