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

HPLC-qTOF-MS/MS-Based Profiling of Flavan-3-ols and Dimeric Proanthocyanidins in Berries of Two Muscadine Grape Hybrids FLH 13-11 and FLH 17-66

FLH 13-11 FL and FLH 17-66 FL are two interspecific hybrid varieties of muscadine grape resulting from the cross of Vitis munsoniana (Simpson) ex Munson and V. rotundifolia. However, profiles of flavan-3-ols and proanthocyanidins in these two hybrids have not been characterized. Herein, we report the use of high-performance liquid chromatography-quadrupole, time-of-flight, tandem mass spectrometry (HPLC-qTOF-MS/MS) to characterize these two groups of metabolites in berries. Ripe berries collected from two consecutive cropping years were used to extract metabolites. Metabolites were ionized using the negative mode. Collision-induced dissociation was performed to fragmentize ions to obtain feature fragment profiles. Based on standards, MS features, and fragments resulted from MS/MS, four flavan-3-ol aglycones, 18 gallated or glycosylated conjugates, and eight dimeric procyanidins, were annotated from berry extracts. Of these 30 metabolites, six are new methylated flavan-3-ol gallates. Furthermore, comparative profiling analysis showed obvious effects of each cultivar on the composition these 30 metabolites, indicating that genotypes control biosynthesis. In addition, cropping seasons altered profiles of these metabolites, showing effects of growing years on metabolic composition. These data are informative to enhance the application of the two cultivars in grape and wine industries in the future.

Protective Effect of Grape Seed Procyanidins against H2 O2 -Induced Oxidative Stress in PC-12 Neuroblastoma Cells: Structure-Activity Relationships

To establish a structure-activity relationship for procyanidins, we verified the cyto-protective effect of 13 grape seed procyanidins, ranging from monomers to trimers against H₂ O₂ -induced oxidative stress in PC-12 neuroblastoma cells. Our study demonstrated some procyanidins were able to significantly protect PC-12 cells from the H₂ O₂ -induced cytotoxicity suggesting they possess neuroprotective effects against oxidative stress. Procyanidins' protective effects against oxidative stress mainly depended on their polymerization degree in addition to their structural features. A positive correlation was found between procyanidins' polymerization degree and the protective effect against oxidative stress in PC-12 cells. The presence of 3- or 3'-galloylated groups in the C-ring of procyanidin molecules significantly increased their protective activity as well. These results demonstrated that galloylated high-molecular-mass procyanidins would be of more interesting as promising antioxidant natural compounds. This work for the first time demonstrated the structure-activity relationships of 13 procyanidins' antioxidative stress activity, which could have a significant impact on future development of procyanidins for healthy food products or drugs to treat disease such as neurodegenerative disorders.

PRACTICAL APPLICATION

This work evaluated the protective effect of procyanidins against oxidative stress in PC-12 neuroblastoma cells and established their activity-structure relationships, which provides useful cellular evidence for the further investigating the structure-optimizing and function-exploiting of procyanidins.

Phenolic Substances in Beer: Structural Diversity, Reactive Potential and Relevance for Brewing Process and Beer Quality

For the past 100 years, polyphenol research has played a central role in brewing science. The class of phenolic substances comprises simple compounds built of 1 phenolic group as well as monomeric and oligomeric flavonoid compounds. As potential anti- or prooxidants, flavor precursors, flavoring agents and as interaction partners with other beer constituents, they influence important beer quality characteristics: flavor, color, colloidal, and flavor stability. The reactive potential of polyphenols is defined by their basic chemical structure, hydroxylation and substitution patterns and degree of polymerization. The quantitative and qualitative profile of phenolic substances in beer is determined by raw material choice. During the malting and brewing process, phenolic compounds undergo changes as they are extracted or enzymatically released, are subjected to heat-induced chemical reactions or are precipitated with or adsorbed to hot and cold trub, yeast cells and stabilization agents. This review presents the current state of knowledge of the composition of phenolic compounds in beer and brewing raw materials with a special focus on their fate from raw materials throughout the malting and brewing process to the final beer. Due to high-performance analytical techniques, new insights have been gained on the structure and function of phenolic substance groups, which have hitherto received little attention. This paper presents important information and current studies on the potential of phenolics to interact with other beer constituents and thus influence quality parameters. The structural features which determine the reactive potential of phenolic substances are discussed.

Isolation and Purification of Two Isoflavones from Hericium erinaceum Mycelium by High-Speed Counter-Current Chromatography

High-speed counter-current chromatography (HSCCC) was used to separate and purify two isoflavones for the first time from Hericium erinaceum (H. erinaceum) mycelium using a two-phase solvent system composed of chloroform-dichloromethane-methanol-water (4:2:3:2, v/v/v/v). These two isoflavones were identified as genistein (4′,5,7-trihydroxyisoflavone, C₁₅H₁₀O₅) and daidzein (4′,7-dihydroxyisoflavone, C₁₅H₁₀O₄), using infrared spectroscopy (IR), electro-spary ionisation mass (ESI-MS), ¹H-nuclear magnetic resonance (NMR) and ¹³C-NMR spectra. About 23 mg genistein with 95.7% purity and 18 mg daidzein with 97.3% purity were isolated from 150 mg ethanolic extract of H. erinaceum mycelium. The results demonstrated that HSCCC was a feasible method to separate and purify genistein and daidzein from H. erinaceum mycelium.

A Strategy for Preparative Separation of 10 Lignans from Justicia procumbens L. by High-Speed Counter-Current Chromatography

Ten compounds, including three lignan glycosides and seven lignans, were purified from Justicia procumbens L. in 8 h using an efficient strategy based on high-speed counter-current chromatography (HSCCC). The two-phase solvent system composed of petroleum–ethyl acetate–methanol–H₂O (1:0.7:1:0.7, v/v) was firstly employed to separate the crude extract (320 mg), from which 19.3 mg of justicidin B (f), 10.8 mg of justicidin A (g), 13.9 mg of 6′-hydroxyjusticidin C (h), 7.7 mg of justicidin E (i), 6.3 mg of lignan J₁ (j) were obtained with 91.3 mg of enriched mixture of compounds a–e. The enriched mixture (91.3 mg) was further separated using the solvent system consisting of petroleum–ethyl acetate–methanol–H₂O (3:3.8:3:3.8, v/v), yielding 12.1 mg of procumbenoside E (a); 7.6 mg of diphyllin-1-O-β-d-apiofuranoside (b); 7.4 mg of diphyllin (c); 8.3 mg of 6′-hydroxy justicidin B (d); and 7.9 mg of diphyllin acetyl apioside (e). The purities of the 10 components were all above 94%, and their structures were identified by NMR and ESI-MS spectra. The results demonstrated that the strategy based on HSCCC for the separation of lignans and their glycosides was efficient and rapid.

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.

Strategies for the extraction and analysis of non-extractable polyphenols from plants

The majority of studies based on phenolic compounds from plants are focused on the extractable fraction derived from an aqueous or aqueous-organic extraction. However, an important fraction of polyphenols is ignored due to the fact that they remain retained in the residue of extraction. They are the so-called non-extractable polyphenols (NEPs) which are high molecular weight polymeric polyphenols or individual low molecular weight phenolics associated to macromolecules. The scarce information available about NEPs shows that these compounds possess interesting biological activities. That is why the interest about the study of these compounds has been increasing in the last years. Furthermore, the extraction and characterization of NEPs are considered a challenge because the developed analytical methodologies present some limitations. Thus, the present literature review summarizes current knowledge of NEPs and the different methodologies for the extraction of these compounds, with a particular focus on hydrolysis treatments. Besides, this review provides information on the most recent developments in the purification, separation, identification and quantification of NEPs from plants.

Natural Phenol Polymers: Recent Advances in Food and Health Applications

Natural phenol polymers are widely represented in nature and include a variety of classes including tannins and lignins as the most prominent. Largely consumed foods are rich sources of phenol polymers, notably black foods traditionally used in East Asia, but other non-edible, easily accessible sources, e.g., seaweeds and wood, have been considered with increasing interest together with waste materials from agro-based industries, primarily grape pomace and other byproducts of fruit and coffee processing. Not in all cases were the main structural components of these materials identified because of their highly heterogeneous nature. The great beneficial effects of natural phenol-based polymers on human health and their potential in improving the quality of food were largely explored, and this review critically addresses the most interesting and innovative reports in the field of nutrition and biomedicine that have appeared in the last five years. Several in vivo human and animal trials supported the proposed use of these materials as food supplements and for amelioration of the health and production of livestock. Biocompatible and stable functional polymers prepared by peroxidase-catalyzed polymerization of natural phenols, as well as natural phenol polymers were exploited as conventional and green plastic additives in smart packaging and food-spoilage prevention applications. The potential of natural phenol polymers in regenerative biomedicine as additives of biomaterials to promote growth and differentiation of osteoblasts is also discussed.