Preparative HSCCC isolation of phloroglucinolysis products from grape seed polymeric proanthocyanidins as new powerful antioxidants

Polyphenol compounds contributing to the improved bioactivities of fermented Rubus chingii Hu

This research aims to evaluate the phenolic composition, antioxidant and enzyme inhibition activities of fermented Rubus chingii Hu wine, and explore the correlation between them. TPC (Total Phenolic content) and TFC (Total Flavonoid content) increased rapidly from 0 h to 72 h, followed by a slight decrease in TPC and a significant decrease in TFC. Fermentation could significantly increase the antioxidant activity and α-amylase/α-glucosidase enzyme inhibitory activity of Rubus chingii Hu. A total of 39 polyphenols and organic acids in fermented Rubus chingii Hu were identified by UPLC-ESI-Q-TOF-MS/MS and 11 of them were quantitatively analyzed. After fermentation, the contents of all the detected polyphenol compounds, except for quercetin and ellagic acid, significantly increased (p < 0.05). Correlation analysis showed that protocatechuic acid and catechin played an important role in the antioxidant activity of fermented Rubus chingii Hu, while protocatechuic acid and hypericin played an important role in the α-amylase inhibition activity. This study indicated that Rubus chingii Hu could be applided as a potential meterial for the wine production, and has the potential to be a functional food for promoting health.

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.

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.

Characterization and Anti-Ultraviolet Radiation Activity of Proanthocyanidin-Rich Extracts from Cinnamomum camphora by Ultrasonic-Assisted Method

The ultrasonic-assisted extraction (UAE) method was employed to separate Cinnamomum camphora proanthocyanidin-rich extracts (PCEs). This extraction process was optimized by the Box-Behnken design, and the optimal conditions, on a laboratory scale, were as follows: an ethanol concentration of 75%, a liquid-to-solid ratio of 24 mL/g, an ultrasonic time of 39 min, and an ultrasonic power of 540 W. Under the obtained conditions, the PCE yield extracted by UAE was higher than that from heat reflux extraction and soaking extraction. An ultra-performance liquid chromatography-tandem mass spectrometry analysis was employed to characterize the phloroglucinolysis products of the C. camphora PCEs, by which epigallocatechin, catechin, epicatechin, and (-)-epigallocatechin-3-O-gallate were identified as the terminal units; epigallocatechin, epicatechin, and (-)-epigallocatechin-3-O-gallate were recognized as extension units. The C. camphora PCEs possessed higher anti-ultraviolet activity in vitro compared with the commercially available sunscreen additive of benzophenone with respect to their ethanol solutions (sun protection factor of 27.01 ± 0.68 versus 1.96 ± 0.07 at a concentration of 0.09 mg/mL) and sunscreens (sun protection factor of 17.36 ± 0.62 versus 14.55 ± 0.47 at a concentration of 20%). These results demonstrate that C. camphora PCEs possess an excellent ultraviolet-protection ability and are promising green sunscreen additives that can replace commercial additives.

Ultrasonic-assisted nanoencapsulation of kiwi leaves proanthocyanidins in liposome delivery system for enhanced biostability and bioavailability

The poor biostability and bioavailability of proanthocyanidins limit their application. In this study, it was hypothesized that encapsulation in lecithin-based nanoliposomes using ultrasonic technology improves the above properties. Based on preliminary experiments, the effects of lecithin mass ratio (1-9%, wt.), pH (3.2-6.8), ultrasonic power (0-540 W), and time (0-10 min) on biostability and bioavailability of purified kiwi leaves proanthocyanidins (PKLPs) were determined. Nanoliposomes prepared optimally with lecithin (5%, wt.), pH = 3.2, ultrasonic power (270 W), and time (5 min) demonstrated a significantly (p < 0.05) improved physicochemical stability, homogeneity, and high encapsulation efficiency (73.84%) relative to control. The PKLPs bioaccessibility during in vitro digestion increased by 2.28-3.07-fold, with a remarkable sustained release and delivery to the small intestine. Similar results were obtained by in vivo analyses, showing over 200% increase in PKLPs bioaccessibility compared to the control. Thus, PKLPs-loaded nanoliposomes are promising candidates for foods and supplements for novel applications.

Structures, Sources, Identification/Quantification Methods, Health Benefits, Bioaccessibility, and Products of Isorhamnetin Glycosides as Phytonutrients

In recent years, people have tended to consume phytonutrients and nutrients in their daily diets. Isorhamnetin glycosides (IGs) are an essential class of flavonoids derived from dietary and medicinal plants such as Opuntia ficus-indica, Hippophae rhamnoides, and Ginkgo biloba. This review summarizes the structures, sources, quantitative and qualitative analysis technologies, health benefits, bioaccessibility, and marketed products of IGs. Routine and innovative assay methods, such as IR, TLC, NMR, UV, MS, HPLC, UPLC, and HSCCC, have been widely used for the characterization and quantification of IGs. All of the therapeutic effects of IGs discovered to date are collected and discussed in this study, with an emphasis on the relevant mechanisms of their health-promoting effects. IGs exhibit diverse biological activities against cancer, diabetes, hepatic diseases, obesity, and thrombosis. They exert therapeutic effects through multiple networks of underlying molecular signaling pathways. Owing to these benefits, IGs could be utilized to make foods and functional foods. IGs exhibit higher bioaccessibility and plasma concentrations and longer average residence time in blood than aglycones. Overall, IGs as phytonutrients are very promising and have excellent application potential.

Characterization, Large-Scale HSCCC Separation and Neuroprotective Effects of Polyphenols from Moringa oleifera Leaves

Moringa oleifera leaves have been widely used for the treatment of inflammation, diabetes, high blood pressure, and other diseases, due to being rich in polyphenols. The main objective of this work was to largely separate the main polyphenols from Moringa oleifera leaves using the technique of high-speed counter-current chromatography (HSCCC). The phenolic composition in Moringa oleifera leaves was first analyzed qualitatively and quantitatively by UPLC-Q-Exactive Orbitrap/MS and UPLC-QqQ/MS, respectively, indicating that quercetin and kaempferol derivatives, phenolic acid and apigenin are the main polyphenols in Moringa oleifera leaves, with quercetin and kaempferol derivatives predominating. Furthermore, the conditions of HSCCC for large-scale separation of polyphenols from Moringa oleifera leaves were optimized, which included the selection of the solvent system, flow rate and the sample load. Only by one-step HSCCC separation (within 120 min) under the optimized conditions, six quercetin and kaempferol derivatives, a phenolic acid and an apigenin could be individually isolated at a large scale (yield from 10% to 98%), each of which possessed high purity. Finally, the isolated polyphenols and phenolic extract from Moringa oleifera leaves (MLPE) were verified to have strong neuroprotective activities against H₂O₂-induced oxidative stress in PC-12 cells, suggesting that these compounds would contribute to the main beneficial effects of Moringa oleifera leaves.

Phenolic compounds in Nordic berry species and their application as potential natural food preservatives

An increasing demand for natural food preservatives is raised by consumers. For Nordic berry species, abundance of phenolic compounds and potent activities of anti-oxidation and anti-bacteria enables a great potential as food preservatives. This review provides a systematic examination of current literature on phenolic profiles, anti-oxidative and anti-bacterial activities of various extracts of Nordic berry species, as well as the impact of various structure features of phenolics on the bioactivities. Special attention is placed on exploitation of leaves of berry species and pomaces after juice-pressing as side-streams of berry production and processing. The current progress and challenges in application of Nordic berry species as food preservatives are discussed. To fully explore the potential application of Nordic berry species in food industry and especially to valorize the side-streams of berry cultivation (leaves) and juice-pressing industry (pomaces), it is crucial to obtain extracts and fractions with targeted phenolic composition, which have high food preserving efficacy and minimal impact on sensory qualities of food products.

Single-step screening and isolation of potential lipoxidase inhibitors from Trifolium repens by stepwise flow rate high-speed countercurrent chromatography and semipreparative high-performance liquid chromatography target-guided by ultrafiltration-LC-MS

An efficient method based on ultrafiltration high-performance liquid chromatography coupled with photodiode array detector and electrospray ionization mass spectrometry for the rapid screening and identified of the ligands for activated from the extract of Trifolium repens L. Five major compounds, namely ononin, daidzein, genistein, formononetin, and biochanin A, were identified as potentially effective inhibitors. Subsequently, the specific binding ligands were separated by stepwise flow rate high-speed countercurrent chromatography and semipreparative high-performance liquid chromatography. This is the first report that T. repens extracts contain potent lipoxidase inhibitors. In summary, we systematically studied the active components in T. repens, evaluated their activity, separated and purified them, and identified their structure. This method is simple, fast, and efficient. It is suitable for the separation and purification of active compounds in T. repens, and provides a theoretical basis and technical platform for the development of natural medicines.

Rapid screening and purification of potential inhibitors from Medicago sativa by ultrafiltration-liquid chromatography combined with stepwise flow rate counter-current chromatography

INTRODUCTION

Medicago sativa contains flavonoids, saponins, coumarins, sterols, monoterpenes, and organic acids, with flavonoids being the main active constituents. Flavonoids naturally contain a 2-phenylchromone structure with antioxidant, free radical scavenging, cardiovascular, and trace estrogen-like effects.

OBJECTIVE

Screening and isolation of neuraminidase, lipoxidase, and lactate dehydrogenase inhibitors from M. sativa via ultrafiltration-liquid chromatography-mass spectrometry (UF-LC-MS) combined with stepwise flow rate counter-current chromatography (CCC).

METHOD

Utilising the medicinal plants M. sativa as the research objects and UF-LC-MS was used for activity screening followed by isolation and purification of the inhibitors by stepwise flow rate CCC. Finally, identification of the three active compounds was achieved by MS and nuclear magnetic resonance.

RESULTS

Three major compounds, viz. quercetin, genistein, and formononetin, were identified as potent neuraminidase, lipoxidase, and lactate dehydrogenase inhibitors, respectively. A two-phase solvent system of ethyl acetate/methanol/n-butanol/water (5.0:1.5:5.0:10; v/v/v/v) was subsequently selected for separation by stepwise flow rate CCC.

CONCLUSION

This novel approach based on UF-LC-MS and stepwise flow rate CCC represents a powerful tool for the screening and isolation of neuraminidase, lipoxidase, and lactate dehydrogenase inhibitors from complex matrices. Therefore, a useful platform for the large-scale production of bioactive and nutraceutical ingredients was developed herein.

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.

Advances in Separation and Purification of Bioactive Polysaccharides through High-speed Counter-Current Chromatography

Polysaccharides, with an extensive distribution in natural products, represent a group of natural bioactive substances having widespread applications in health-care food products and as biomaterials. Devising an efficient system for the separation and purification of polysaccharides from natural sources, hence, is of utmost importance in the widespread applicability and feasibility of research for the development of polysaccharide-based products. High-speed counter-current chromatography (HSCCC) is a continuous liquid-liquid partitioning chromatography with the ability to support a high loading amount and crude material treatment. Due to its flexible two-phase solvent system, HSCCC has been successfully used in the separation of many natural products. Based on HSCCC unique advantages over general column chromatography and its enhanced superiority in this regard when coupled to aqueous two-phase system (ATPS), this review summarizes the separation and purification of various bioactive polysaccharides through HSCCC and its coupling to ATPS as an aid in future research in this direction.

Production of oligomeric procyanidins by mild steam explosion treatment of grape seeds

BACKGROUND

Sixty five percent of procyanidins in grape seeds is polymeric procyanidins (PPC), and they could not be assimilated directly by human. To enhance procyanidin assimilation, steam explosion treatment (SE) was used to facilitate the preparation of oligomeric procyanidins (OPC) from grape seeds.

RESULTS

The results indicate that SE treatment made grape seeds loose and porous, and decreased the mean degree of polymerization (mDP) of procyanidins. The procyanidins content and total phenolic content (TPC) were decreased with the increase of SE severity, while the amount of catechin (CA), epicatechin (EC) and epicatechin-3-O-gallate (ECG) were increased, resulting in significant increase of antioxidant activity.

CONCLUSIONS

Although SE treatment could depolymerize PPC and produce CA/EC/ECG with high yield, it caused the yield loss of total procyanidins. SE treatment is a potential effective method to prepare procyanidins with low degree of polymerization and high antioxidant activity. However, it still needs to study further how to balance the yield of total procyanidins and catechin monomers (CA/EC/ECG).

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.

A quick, accurate and general ultra performance liquid chromatography method for evaluating the quality of enological tannins

Commercial enological tannins from various origins have been widely used in modern wine making. In order to investigate the diverse quality of tannin products, a quick, accurate and simple UPLC method was developed, which could simultaneously determine 11 principle characteristic components of hydrolysable tannins and condensed tannins. The optimum resolution of the tannins was achieved on a Waters Acquity UPLC-BEH C18 column (2.1 mm × 50 mm, 1.7 μm) at 280 nm with gradient elution. The method was validated to achieve desired specificity, linearity, precision, accuracy and stability. The developed method was successfully applied to 30 commercial enological tannins from different origins for their quality evaluation. The 30 tannin samples were qualitatively distinguished into hydrolysable, condensed or mixture tannins, and quantificationally classified into four levels of excellent, good, fair and poor products. The method could be used for quick evaluating the quality of enological tannins in practical use.

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.

Effect of tannin addition on chromatic characteristics, sensory qualities and antioxidant activities of red wines

Tannin addition as an enological practice has been widely used in the winemaking process because of their ability of improving the aroma and sensory characteristics and stabilizing of color of red wine. In this study, hydrolysable, condensed tannins and their mixtures in different ratios were added into two Merlot wines to investigate their effect on the wine overall quality. The contents of 15 phenolic compounds were detected by HPLC-DAD, CIELAB color parameters were measured using a chromatic aberration meter, sensory evaluation was accomplished using the assessment standards established by the American Wine Association, and antioxidant activities were analyzed using DPPH and ABTS radical tests. The results indicated that adding tannins affected phenolic composition, contents and color of wine. The specific effects varied by tannins. Furthermore, tannin addition, especially the mixed tannins, improved the sensory qualities and antioxidant activities greatly. The mixed tannins added with a ratio of 1 : 1 between hydrolyzable and condensed tannins exhibited a better effect on both sensory qualities and antioxidant activities, and it could be recommended as an ideal tannin addition for wine quality improvement.

The effect of tannin addition on the wine overall quality were investigated and an ideal tannin addition was recommended for wine quality improving.

Novel flavan-3-ol-glutathione conjugates from the degradation of proanthocyanidins as highly bioactive antioxidants

Synthesis, preparation and antioxidant capacity evaluation of flavan-3-ol-glutathione conjugates.

Comparison of the phenolic profiles and physicochemical properties of different varieties of thermally processed canned lychee pulp

Lychee pulp is rich in phenolics and has a variety of biological activities. However, the changes in the phenolic profile under heat treatment are unknown. The effect of the heat treatment temperature on commercial varieties (Guiwei and Nuomici) of canned lychee was investigated by comparing samples that were either unheated (UH), underwent 70 °C heat treatment (HT70) or underwent 121 °C heat treatment (HT121) and then were stored at room temperature. The results showed that the total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity of the UH, HT70 and HT121 samples were significantly decreased after storage at room temperature for 9 d, 13 d and 25 d, respectively. However, the TPC, TFC and antioxidant activity of HT121 canned lychee were still significantly higher than those of the UH and HT70 samples. However, the texture characteristics of the HT121 samples were worse than those of the UH and HT70 samples, and the color of the canned lychee was darker after the HT121 treatment. Nine individual phenolic compounds were detected in the canned lychee by HPLC-DAD. The gallic acid content was increased after HT121 treatment. In particular, (−)-gallocatechin was generated by HT121 thermal processing. However, after storage at room temperature for 9 d, the contents of (−)-gallocatechin in canned Guiwei and Nuomici were decreased by 96.27% and 94.04%, respectively, and (−)-gallocatechin disappeared after 25 d. In summary, the phenolic contents and antioxidant activity of canned lychee are increased by high-temperature treatment.

Lychee pulp is rich in phenolics and has a variety of biological activities.

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.

Bioactivity-Guided Separation of Potential D₂ Dopamine Receptor Antagonists from Aurantii Fructus based on Molecular Docking Combined with High-Speed Counter-Current Chromatography

The typical compounds of Aurantii fructus (AF) reported in previous research were screened for their high antagonistic ability on the D₂ dopamine receptor (D₂R) in silico, and then bioactivity-guided separation was undertaken on the potential D₂R antagonists from AF using high-speed counter-current chromatography (HSCCC). Three flavanones, two polymethoxyflavonoids, and three coumarins were effectively isolated from ethanol extracts of Aurantii fructus (AF) by the use of a two-step HSCCC method, and their chemical structures were identified by mass spectrometry, ¹H-NMR, and ¹³C-NMR and compared with published data. Firstly, crude extract of 70% ethanol eluent (150 mg) was isolated by HSCCC using an n-hexane−ethyl acetate−n-butanol−methanol−0.05% acetic acid (1:3:1.8:1:5, v/v/v/v/v) solvent system, and compounds 1 (naringin, 28 mg), 2 (neohesperidin, 13 mg), 3 (meranzin, 5 mg) and 4 (poncirin, 3 mg) were successfully isolated with 98.5%, 95.1%, 97.7%, and 92.4% purity, respectively. Then, the crude extract of 95% ethanol eluent (120 mg) was isolated by n-hexane−n-butanol−ethanol (methanol)−0.05% acetic acid (2:0.6:1:3, v/v/v/v) solvent system and compounds 3 (meranzin, 3 mg), 5 (meranzin hydrate, 4 mg), 6 (isomeranzin, 6 mg), 7 (nobiletin, 10 mg), and 8 (tangeretin, 7 mg) were successfully isolated with 95.8%, 98.5%, 95.1%, 92.4%, and 97.7% purity, respectively. Naringenin, a parent structure of naringin with the excellent binding score of −9.3 kcal/mol, was completely in conjunction with the active site of D₂R, indicating that it is critical for the treatment of gastrointestinal dysfunction. The results indicated that the bioactivity-guided method is practical for the effective separation of active compounds from natural resources.

Antisolvent precipitation for the preparation of high polymeric procyanidin nanoparticles under ultrasonication and evaluation of their antioxidant activity in vitro

An improved method of ultrasonic antisolvent precipitation was used to prepare micronized high polymeric procyanidins (HPC). Response surface methodology (Plackett-Burman and Box-Behnken design) was employed to predict the optimal preparation conditions and satisfactory mean particle size. Among seven parameters, three parameters (i.e., ultrasonic irradiation power, ultrasonic-stirring time, and stirring speed) were identified as the most significant variables using Plackett-Burman design; thus, these three parameters were further optimized using Box-Behnken design. The optimal preparation conditions for micronized HPC were obtained as follows: dropping speed of 4 mL/min, HPC solution concentration of 0.3 mg/mL, ratio of antisolvent and solvent of 5 mL/mL, precipitation temperature of 10 °C, ultrasonic-stirring time of 14 min, ultrasonic irradiation power of 620 W, and stirring speed of 760 r/min. A minimum mean particle size of 96 ± 2 nm was achieved under the aforementioned conditions. The obtained micronized HPC was analysed by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric and X-ray powder diffraction patterns. Micronized HPC enjoyed the higher quantity dissolved and exhibited stronger antioxidant activity in compared to the unprocessed HPC. These results demonstrated that the improved method has great potential for the production of micronized particles.

Oxidative Stress and Heavy Metals in Plants

Oxidative stress is a pathological process related to not only animal kingdom but also plants. Regarding oxidative stress in plants, heavy metals are frequently discussed as causative stimuli with relevance to ecology. Because heavy metals have broad technological importance, they can easily contaminate the environment. Much of previous effort regarding the harmful impact of the heavy metals was given to their toxicology in the animals and humans. Their implication in plant pathogeneses is less known and remains underestimated.The current paper summarizes basic facts about heavy metals, their distribution in soil, mobility, accumulation by plants, and initiation of oxidative stress including the decline in basal metabolism. The both actual and frontier studies in the field are summarized and discussed. The major pathophysiological pathways are introduced as well and link between heavy metals toxicity and their ability to initiate an oxidative damage is provided. Mobility and bioaccessibility of the metals is also considered as key factors in their impact on oxidative stress development in the plant. The metals like lead, mercury, copper, cadmium, iron, zinc, nickel, vanadium are depicted in the text.Heavy metals appear to be significant contributors to pathological processes in the plants and oxidative stress is probably an important contributor to the effect. The most sensitive plant species are enlisted and discussed in this review. The facts presented here outline next effort to investigate pathological processes in the plants.

Grape and wine polymeric polyphenols: Their importance in enology

Phenolic compounds are important constituents of red wine, contributing to its sensory properties and antioxidant activity. Owing to the diversity and structural complexity, study of these compounds was mainly limited, during the last three decades, on their low-molecular-mass compounds or simple phenolic compounds. Only in recent years, much attention has been paid to highly polymerized polyphenols in grape and red wines. The reason for this is largely due to the development of analytical techniques, especially those of HPLC-ESI-MS, permitting the structural characterization of highly polymerized polyphenols. Furthermore, the knowledge on the biological properties of polymeric polyphenols of red wine is very limited. Grape polyphenols mainly consist of proanthocyanidins (oligomers and polymers) and anthocyanins, and low amount of other phenolics. Red wine polyphenols include both grape polyphenols and new phenolic products formed from them during winemaking process. This leads to a great diversity of new polyphenols and makes wine polyphenol composition more complex. The present paper summarizes the advances in the research of polymeric polyphenols in grape and red wine and their important role in Enology. Scientific results indicate that polymeric polyphenols, as the major polyphenols in grape and red wine, play a major role in red wine sensory properties, color stability and antioxidant activities.

Efficient approach for the extraction of proanthocyanidins from Cinnamomum longepaniculatum leaves using ultrasonic irradiation and an evaluation of their inhibition activity on digestive enzymes and antioxidant activity in vitro

Proanthocyanidins were separated for the first time from Cinnamomum longepaniculatum leaves. An experiment-based extraction strategy was used to research the efficiency of an ultrasound-assisted method for proanthocyanidins extraction. The Plackett-Burman design results revealed that the ultrasonication time, ultrasonic power and liquid/solid ratio were the most significant parameters among the six variables in the extraction process. Upon further optimization of the Box-Behnken design, the optimal conditions were obtained as follows: extraction temperature, 100°C; ethanol concentration, 70%; pH 5; ultrasonication power, 660 W; ultrasonication time, 44 min; liquid/solid ratio, 20 mL/g. Under the obtained conditions, the extraction yield of the proanthocyanidins using the ultrasonic-assisted method was 7.88 ± 0.21 mg/g, which is higher than that obtained using traditional methods. The phloroglucinolysis products of the proanthocyanidins, including the terminal units and derivatives from the extension units, were tentatively identified using a liquid chromatography with tandem mass spectrometry analysis. Cinnamomum longepaniculatum proanthocyanidins have promising antioxidant and anti-nutritional properties. In summary, an ultrasound-assisted method in combination with a response surface experimental design is an efficient methodology for the sufficient isolation of proanthocyanidins from Cinnamomum longepaniculatum leaves, and this method could be used for the separation of other bioactive compounds.

Thinned stone fruits are a source of polyphenols and antioxidant compounds

BACKGROUND

Thinned fruits are agricultural by-products that contain large quantities of interesting compounds due to their early maturity stage. In this work, the phenolic profile and the antioxidant activity of six thinned stone fruits (apricot, cherry, flat peach, peach, plum and nectarine) have been investigated, focussing on proanthocyanidins.

RESULTS

Thinned nectarine had the highest content of total phenols [67.43 mg gallic acid equivalents (GAE) g^-1 dry weight (DW)] and total flavonoids (56.97 mg CE g^-1 DW) as well as the highest antioxidant activity measured by DPPH scavenging (133.30 mg [Trolox equivalents (TE) g^-1 DW] and FRAP assay (30.42 mg TE g^-1 DW). Proanthocyanidins were very abundant in these by-products, and the main phenolic group quantified in cherry (10.54 mg g^-1 DW), flat peach (33.47 mg g^-1 DW) and nectarine (59.89 mg g^-1 DW), while hydroxycinnamic acids predominate in apricot, peach and plum (6.67, 22.04 and 23.75 mg g^-1 DW, respectively). The low, mean degree of polymerisation of proanthocyanidins suggests that their bioavailability could be very high.

CONCLUSIONS

This study shows that thinned stone fruit extracts might be used as antioxidants in foods or as a source of compounds with health-related benefits that can be used in the pharmaceutical, cosmetic and food industries. © 2016 Society of Chemical Industry.

Preparative separation of cacao bean procyanidins by high-speed counter-current chromatography

In this work, an efficient method for preparative separation of procyanidins from raw cacao bean extract by high-speed counter-current chromatography (HSCCC) was developed. Under the optimized solvent system of n-hexane-ethyl acetate-water (1:50:50, v/v/v) with a combination of head-tail and tail-head elution modes, various procyanidins fractions with different polymerization degrees were successfully separated. UPLC, QTOF-MS and ¹H NMR analysis verified that these fractions contained monomer up to pentamer respectively. Dimeric procyanidin B2 (purity>86%) could be isolated by HSCCC in a single run. Other individual procyanidins in these fractions could be further isolated and purified by preparative HPLC. The developed HSCCC together with preparative HPLC techniques appeared to be a useful tool for large preparation of different procyanidins from cacao beans. Furthermore, by antioxidant activity assays, it was proved that both fractions and individual procyanidins possessed greater antioxidant activities compared to standard trolox. The antioxidant activities of procyanidins increase as the increase of their polymerization degree.

Optimization of the Ultrasonic-Assisted Extraction of Bioactive Flavonoids from Ampelopsis grossedentata and Subsequent Separation and Purification of Two Flavonoid Aglycones by High-Speed Counter-Current Chromatography

The fermented leaf of Ampelopsis grossedentata has been used as a beverage and folk medicine called "vine tea" in the southern region of China. In this paper, the optimum extraction conditions for the maximum recovery amounts of total flavonoids (TF), dihydromyricetin (DMY), myricitrin (MYG) and myricetin (MY) from natural Ampelopsis grossedentata leaves subjected to ultrasonic-assisted extraction (UAE) were determined and optimized by using response surface methodology. The method was employed by the Box-Behnken design (BBD) and Derringer's desirability function using methanol concentration, extraction time, liquid/solid ratio as factors and the contents of TF, DMY, MYG and MY as responses. The obtained optimum UAE conditions were as follows: a solvent of 80.87% methanol, an extraction time of 31.98 min and a liquid/solid ratio of 41.64:1 mL/g. Through analysis of the response surface, it implied that methanol concentration and the liquid/solid ratio had significant effects on TF, DMY, MYG and MY yields, whereas extraction time had relatively little effects. The established extraction and analytical methods were successfully applied to determine the contents of the total flavonoids and three individual flavonoids in 10 batches of the leaf samples of A. grossedentata from three counties in Fujian Province, China. The results suggested the variability in the quality of A. grossedentata leaves from different origins. In addition, high purities of dihydromyricetin and myricetin were simultaneously separated and purified from the extract subjected to optimized UAE, by high-speed counter-current chromatography using a solvent system of N-hexane-ethyl acetate-methanol-water (1:3:2:4; v/v/v/v). In a single operation, 200 mg of the extract were separated to yield 86.46 mg of dihydromyricetin and 3.61 mg of myricetin with the purity of 95.03% and 99.21%, respectively. The results would be beneficial for further exploiting the herbal products and controlling the quality of the herb and its derived products.

Characterization and preparation of oligomeric procyanidins from Litchi chinensis pericarp

The main purpose of this study is to characterize and prepare A-type oligomeric procyanidins from litchi pericarp (Litchi chinensis Baila). The variety of oligomeric procyanidins was characterized by LC-ESI-MS analysis. There were (+)-catechin, (-)-epicatechin, twelve dimers and six trimers of procyanidins were found in litchi pericarp extracts, and A-type procyanidins were much more abundant than B-type procyanidins. The main flavan-3-ol monomer and oligomeric procyanidins in litchi pericarp were (-)-epicatechin, A-type dimers (A1 and A2) and trimer (epicatechin-(4β-8, 2β-O-7)-epicatechin- (4β-8)-epicatechin). Procyanidin A1 (epicatechin-(4β-8, 2β-O-7)-catechin) was identified by NMR in litchi pericarp for the first time. (-)-Epicatechin and oligomeric procyanidins were prepared by the combination of AB-8 column chromatography and Toyopearl HW-40S column chromatography. The results showed that each fraction predominantly owned a single compound and gave a high yield with (-)-epicatechin, A-type dimers (A1 and A2) and trimer, suggesting a useful method to obtain pure (-)-epicatechin and A-type oligomeric procyanidins.