Polymeric Procyanidins Research Articles

The content of phenolic compounds in leaf tissues of Aesculus glabra and Aesculus parviflora walt.

In plants, flavonoids play an important role in biological processes. They are involved in UV-scavenging, fertility and disease resistance. Therefore, in this study, we attempted to quantify and characterize phenolic compounds in Aesculus parviflora Walt. leaves and Aesculus glabra leaves partly suffering from attack by a leaf mining insect (C. ohridella). A total of 28 phenolic compounds belonging to the hydroxycinnamic acid, flavan-3-ols and flavonol groups were identified and quantified in Aesculus parviflora and A. glabra leaf extracts. Significantly decreased concentrations of some phenolic compounds, especially of flavan-3-ols, were observed in infected leaves compared to the non-infected ones. Additionally, a higher content of polymeric procyanidins in leaves of Aesculus parviflora than in Aesculus glabra may explain their greater resistance to C. ohridella insects.

Oligomeric cocoa procyanidins possess enhanced bioactivity compared to monomeric and polymeric cocoa procyanidins for preventing the development of obesity, insulin resistance, and impaired glucose tolerance during high‐fat feeding (LB331)

There is interest in the potential of cocoa flavanols, including monomers and procyanidins, to prevent obesity and type‐2 diabetes. Fermentation and processing of cocoa beans influence the qualitative and quantitative profiles of individual cocoa constituents. Little is known regarding how different cocoa flavanols contribute to inhibition of obesity and type‐2 diabetes. The objective of this study was to compare the impacts of long‐term dietary exposure to cocoa flavanol monomers, oligomers and polymers on the effects of high‐fat feeding. Mice were fed a high‐fat diet supplemented with either a cocoa flavanol extract, or a flavanol fraction enriched with monomeric, oligomeric, or polymeric procyanidins for 12 weeks. The oligomer‐rich fraction proved to be most effective in preventing weight gain, fat mass, impaired glucose tolerance, and insulin resistance in this model. This is the first long‐term feeding study to examine the relative activities of cocoa constituents on diet‐induced obesity and insulin resistance.

Changes in Plasma Phenolic Metabolites of Rats Administered Different Molecular-Weight Polyphenol Fractions from Chinese Quince Fruit Extracts

Chinese quince is a medicinal fruit rich in polyphenols. We investigated the effects of oral administration of Chinese quince polyphenols extracted with boiling water on plasma phenolic metabolites in rats. Plasma vanillic acid concentration increased for 6 h after administration of both low molecular-weight polyphenolic fraction (LMW-F) and high molecular-weight polyphenolic fraction (HMW-F). The increase in plasma vanillic acid in the HMW-F group was 2.1 times greater than that in the LMW-F group. (–)-Epicatechin and 3-hydroxyphenylpropionic acid were detected only in the plasma of the LMW-F group. Plasma concentrations of protocatechuic and 3-hydroxyphenylacetic acids increased 2 h after administration of LMW-F, whereas only a slight increase after 6 h was observed in the HMW-F group. These results suggest that LMW-F could potentially increase various plasma metabolites, including (–)-epicatechin, and that HMW-F, which mainly consists of procyanidin polymers, could increase plasma vanillic acid after ingestion. Practical Applications Chinese quince (Pseudocydonia sinensis) fruit has been used in traditional Chinese and Japanese medicinal foods. According to the results of our animal experiments, Chinese quince polyphenols extracted with boiling water can increase plasma vanillic acid concentration after ingestion. Vanillic acid has various potential health benefits including anti-inflammatory properties. Hence Chinese quince could be a source of vanillic acid, a pharmacological factor in vivo.

Oligomeric Cocoa Procyanidins Possess Enhanced Bioactivity Compared to Monomeric and Polymeric Cocoa Procyanidins for Preventing the Development of Obesity, Insulin Resistance, and Impaired Glucose Tolerance during High-Fat Feeding

There is interest in the potential of cocoa flavanols, including monomers and procyanidins, to prevent obesity and type-2 diabetes. Fermentation and processing of cocoa beans influence the qualitative and quantitative profiles of individual cocoa constituents. Little is known regarding how different cocoa flavanols contribute to inhibition of obesity and type-2 diabetes. The objective of this study was to compare the impacts of long-term dietary exposure to cocoa flavanol monomers, oligomers, and polymers on the effects of high-fat feeding. Mice were fed a high-fat diet supplemented with either a cocoa flavanol extract or a flavanol fraction enriched with monomeric, oligomeric, or polymeric procyanidins for 12 weeks. The oligomer-rich fraction proved to be most effective in preventing weight gain, fat mass, impaired glucose tolerance, and insulin resistance in this model. This is the first long-term feeding study to examine the relative activities of cocoa constituents on diet-induced obesity and insulin resistance.

Preparative isolation of monomer catechins and oligomer procyanidin fractions from grape seed extracts by high-speed counter-current chromatography

In this paper, monomer (+)-catechin; (-)-epicatechin and (-)-epicatechin-3-o-gallate, three oligomeric procyanidin fractions (OPCs) and one polymeric procyanidin fractions (PPCs) were successfully separated and isolated from grape seed extracts using semi-preparative TBE-300 B high-speed counter-current chromatography (HSCCC). For their separation in monomer (+)-catechin; (-)-epicatechin and (-)-epicatechin 3-O-gallate, hexane/ethyl acetate/water (1:10: 10, v/v/v) was selected as solvent system. For separation of OPCs and PPCs, solvent system ethyl acetate/water (1:1, v/v) was selected. Compositional data and mean polymerization degrees of OPCs were determined by phloroglucinolysis method. The purity of each fraction obtained; monomer (+)-catechin (C), (-)-epicatechin (EC) and (-)-epicatechin-3-o-gallate (ECG), verified by UPLC, was 98%, 82% and 71%, respectively. The mean polymerization degrees of the three OPCs fractions were respectively 2.842, 3.521, 4.475. As compared with traditional separation methods for catechins and OPCs, HSCCC has shown to be a powerful and efficient technique for large-scale isolation of these compounds.

Variability of Phytochemical Properties and Content of Bioactive Compounds in Lonicera caerulea L. var. kamtschatica Berries

Phytochemical profiles of four different honeysuckle varieties and four genotypes were studied. Polyphenols were identified by LC-PDA-QTOF/MS and quantified by UPLC-PDA and UPLC-FL. A total of 21 polyphenolic compounds found in the investigated fruit tissues were identified and presented as 6 anthocyanins, 6 flavan-3-ols, 4 phenolic acids, 3 flavanols, and 2 flavones. Among the identified compounds polymeric procyanidins and one luteolin derivative were quantified for the first time. Anthocyanins and flavan-3-ols were the major classes of honeysuckle polyphenols. The content of total polyphenols was between 775 mg (genotype 'Klon 38') and 2005 mg/100 g dry matter (cultivar 'Duet'). The content of ascorbic acid ranged from 3.19 to 32.12 mg/100 g fresh matter for genotypes 'Klon C' and 'Klon 44', respectively. The content of polyphenolic compounds was highly correlated with the antioxidant activity. Some honeysuckle genotypes may be deemed interesting as applicable in human nutrition.

Downregulated Lipid Metabolism in Differentiated Murine Adipocytes by Procyanidins from Defatted Grape Seed Meal

Recent reports have proposed possible anti-obesity mechanisms for antioxidants involving increased energy expenditure, pre-adipocyte differentiation and proliferation, decreased lipogenesis and increased lipolysis, and fat oxidation. The aim of this study was to examine and to confirm the anti-obesity effect of the oligomeric and polymeric procyanidin fractions from defatted grape seeds. The lipid metabolism-related mRNA level in the mouse preadipocytes, 3T3-L1 cells, was determined to evaluate the anti-obesity effect of the phenolic fractions from a grape seed meal. Lipid accumulation was reduced by 19% of the control level by the procyanidin fraction originating from the grape seed meal. Emerging from the effect of the treatment on HSL and LPL mRNA expression, lipolytic enzyme activity was not involved in the anti-obesity effects of CPE and FPP from the defatted grape seed meal. We tested and confirmed in this study the effect of the biological activities of oligomeric and polymeric procyanidins from the defatted grape seed meal. It is suggested from the results of this brief study that further studies would be desirable to focus on the anti-obesity effect of the purified extracts of a defatted grape seed meal.

Polymeric procyanidin fraction from defatted grape seeds protects HepG2 cells against oxidative stress by inducing phase II enzymes via Nrf2 activation

Nuclear factor erythroid 2-related factor 2 (Nrf2) is an important transcription factor that regulates antioxidant response element (ARE)-driven phase II detoxification enzymes. In this study, induction of phase II enzymes via Nrf2/ARE activation in the cytoprotective effect of crude polyphenol extract (CPE), oligomeric procyanidin fraction (OPF), and polymeric procyanidin fraction (PPF) from defatted grape seeds in HepG2 cells was evaluated. Among these treatments, the treatment with PPF significantly increased Nrf2 protein expression in the nuclear fraction. Treating the samples increased heme oxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase 1 (NQO1) protein expression in a dose-dependent manner, and PPF significantly increased the levels of phase II enzymes. Cellular generation of reactive oxygen species (ROS) were effectively reduced by PPF. These results suggest that pretreatment with PPF shows a cytoprotective effect by inhibiting ROS production and inducing HO-1 and NQO1 expression via Nrf2 activation in HepG2 cells.

Detailed Polyphenol and Tannin Composition and Its Variability in Tunisian Dates (Phoenix dactylifera L.) at Different Maturity Stages

The polyphenol profile of two Tunisian varieties of dates including flavanols, flavonols, flavones, and hydroxycinnamates was characterized. Three tissue zones (flesh, peel, and stone) and three maturity stages were considered. Phenolic compounds were analyzed using reversed phase high-performance liquid chromatography coupled to UV-visible and electrospray mass spectrometry. Procyanidin oligomers and polymers were characterized and quantified using phloroglucinolysis prior to HPLC analysis. Procyanidin polymers based on (-)-epicatechin structure were by far the most concentrated polyphenols in ripe dates, accounting for 95% of total polyphenols with an average concentration of 14 g/kg in the fresh edible parts of the fruit. Interestingly, procyanidins were also highly concentrated in the stones. The concentration and average degree of polymerization (DPn) of the procyanidins decreased according to maturity. Other phenolics, including caffeoylshikimic acid hexoside, caffeoyl-sinapoyl monohexoside and dihexoside, and acetylated flavonols, were tentatively identified for the first time in the fruit.

Compositional and Sensory Characterization of Red Wine Polymers

After isolation from red wine by means of ultrafiltration and gel adsorption chromatography, the composition of the highly astringent tasting high-molecular weight polymers was analyzed by means of HPLC-MS/MS, HPLC-UV/vis, and ion chromatography after thiolytic, alkaline, and acidic depolymerization and, on the basis of the quantitative data obtained as well as model incubation experiments, key structural features of the red wine polymers were proposed. The structural backbone of the polymers seems to be comprised of a procyanidin chain with (-)-epicatechin, (+)-catechin, (-)-epicatechin-3-O-gallate units as extension and terminal units as well as (-)-epigallocatechin as extension units. In addition, acetaldehyde was shown to link different procyanidins at the A-ring via an 1,1-ethylene bridge and anthocyanins and pyranoanthocyanins were found to be linked to the procyanidin backbone via a C-C-linkage at position C(6) or C(8), respectively. Alkaline hydrolysis demonstrated the polymeric procyanidins to be esterified with various organic acids and phenolic acids, respectively. In addition, the major part of the polysaccharides present in the red wine polymeric fraction were found not to be covalently linked to procyanidins. Interestingly, sensory evaluation of individual fractions of the red wine polymers did not show any significant difference in the astringent threshold concentrations, nor in the astringency intensity in supra-threshold concentrations and demonstrated the mean degree of polymerization as well as the galloylation degree not to have an significant influence on the astringency perception.

Vasorelaxant and antihypertensive effects of methanolic extracts from Hymenocardia acida Tul

Ethnopharmacological relevanceIn Congolese traditional medicine, decoctions of Hymenocardia acida root bark (HaRB) and trunk bark (HaTrB) are used for the treatment of conditions assumed to be hypertension. In this work, we propose to study the vasorelaxant effect of HaRB and HaTrB methanolic extracts on isolated rat thoracic aorta, to characterize the group of molecules responsible for the observed vasorelaxant activity, to evaluate the in vitro antioxidant activity of these extracts and to determine the antihypertensive activity of the HaRB extract on spontaneously hypertensive rats (SHR). Materials and methodsThe vasorelaxant effect of the HaRB and HaTrB methanolic extracts was studied on endothelium-intact aortic rings pre-contracted with phenylephrine (PE, 1μM). The mechanism of this vasorelaxant effect was investigated on endothelium-denuded vessels and on endothelium-intact aortic rings in the presence of three inhibitors: l-NG-nitroarginine methyl ester (100μM), indomethacin (10μM) and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (10μM). To determine the nature of the compounds responsible for the vasorelaxant activity, we carried out a fractionation of the extracts and a thiolysis of the most active fraction followed by a liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) analysis. The extracts antioxidant activity was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) colorimetric assay. In vivo anti-hypertensive activity of the HaRB extract was conducted on SHR. ResultsHaRB and HaTrB methanolic extracts produced a concentration-dependent vasorelaxation on intact aortic rings pre-contracted with PE (1μM). The vasorelaxant responses obtained were 95.3±1.5% (5μg/ml) and 100.6±3.0% (1μg/ml), respectively. The effect was markedly attenuated by removal of endothelium or pretreatment of aortic rings with all inhibitors except indomethacin. The LC/ESI-MS analysis of the thiolysis products indicated that the fraction which caused the most important vasorelaxation (97.9±2.5% at 3μg/ml) was a mixture of procyanidins and prodelphinidins, with a predominance of procyanidins. Both extracts and all fractions from HaRB extract showed a DPPH scavenging activity, ranging from 0.4 to 0.8 quercetin-equivalents. The HaRB methanolic extract reduced the systolic blood pressure in SHR (from 214±3mmHg to 194±4mmHg) after a 5-week treatment. ConclusionsThe methanolic extracts of Hymenocardia acida root and trunk bark have vasorelaxant activity. The vasorelaxant effect observed is endothelium-dependent and seems mainly mediated through the NO-cGMP pathway. The COX pathway is not involved. The vasorelaxant activity appears to be due to polymeric procyanidins and prodelphinidins. These extracts also have an antioxidant effect. The extract of Hymenocardia acida root bark shows a significant but weak antihypertensive activity in SHR.

Reactivity of Polymeric Proanthocyanidins toward Salivary Proteins and Their Contribution to Young Red Wine Astringency

Recent studies have indicated the presence of significant amount of highly polymerized and soluble proanthocyanidins in red wine and such compounds interacted readily with proteins, suggesting that they might be particularly astringent. Thus, the objective of this work was to verify the astringency of polymeric proanthocyanidins and their contribution to red wine astringency. The precipitation reactions of the purified oligomeric procyanidins (degree of polymerization ranging from 2 to 12-15) and polymeric procyanidins (degree of polymerization ranging from 12-15 to 32-34) with human salivary proteins were studied; salivary proteins composition changes before and after the reaction was verified by SDS-PAGE and procyanidins composition changes by spectrometric, direct HPLC and thiolysis-HPLC methods. The astringency intensity of these two procyanidin fractions was evaluated by a sensory analysis panel. For verifying the correlation between polymeric proanthocyanidins and young red wine astringency, the levels of total oligomeric and total polymeric proanthocyanidins and other phenolic composition in various young red wines were quantified and the astringency intensities of these wines were evaluated by a sensory panel. The results showed that polymeric proanthocyanidins had much higher reactivity toward human salivary proteins and higher astringency intensity than the oligomeric ones. Furthermore, young red wine astringency intensities were highly correlated to levels of polymeric proanthocyanidins, particularly at low concentration range (correlation coefficient r = 0.9840) but not significant correlated to total polyphenols (r = 0.2343) or other individual phenolic compounds (generally r < 0.3). These results indicate the important contribution of polymeric proanthocyanidins to red wine astringency and the levels of polymeric polyphenols in red wines may be used as an indicator for its astringency.

Protective effects of oligomeric and polymeric procyanidin fractions from defatted grape seeds on tert-butyl hydroperoxide-induced oxidative damage in HepG2 cells

Oligomeric and polymeric procyanidins have been reported to possess different antioxidant capacities. However, the intracellular antioxidant mechanisms of oligomeric and polymeric procyanidins are still poorly understood. In this study, we evaluated the cytoprotective effects of the oligomeric procyanidin fraction (OPF) and the polymeric procyanidin fraction (PPF) from grape seeds against the oxidative damage induced by tert-butyl hydroperoxide (TBHP) in HepG2 cells. The levels of cellular reactive oxygen species (ROS), cellular lipid peroxidation, glutathione (GSH), and antioxidant enzyme activities were measured as biomarkers of cellular oxidative status. HepG2 cells were treated with different concentrations of procyanidin samples (0–20μg/ml) for 6h prior to treatment with TBHP for 3h. The incubation of HepG2 cells with TBHP led to an approximately 60% decrease in cell viability. However, pretreatment of the cells with the samples, at 5–20μg/ml, rescued cell viability in a dose-dependent manner. Cellular generation of ROS, formation of malondialdehyde (MDA), and depletion of GSH were reduced by OPF and PPF. Moreover, TBHP treatment increased the activities of glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase (SOD). However, a 6h pretreatment with each of the samples at 20μg/ml significantly decreased the activities of these enzymes. These results clearly showed that treatment with OPF and PPF protected against oxidative damage by modulating ROS production, GSH levels, MDA generation, and antioxidant enzyme activities in HepG2 cells.

Mass Spectroscopic Methods for the Characterization of Flavonoid Compounds

Flavonoids are a broad class of polyphenolic secondary metabolites widely dispersed throughout the plant kingdom and found in substantial levels in commonly consumed fruits, vegetables and beverages. These compounds have aroused considerable interest because of their potential beneficial biochemical and antioxidant effects on human health. The structures of flavonoids are characterized by a fifteen-carbon backbone consisting of two aromatic and one oxygenated rings. Flavonoids could be divided into various types of monomeric aglycones, bi-, tri-, and oligo-flavonoids including proanthocyanidins. Owing to the importance of flavonoids, isolation and structural elucidation of natural flavonoids play an important role in many areas of science. This is generally performed by a combination of chromatographic and spectroscopic methods, including ultraviolet, nuclear magnetic resonance and mass spectrometry. Among all these techniques, mass spectrometry remains an important tool for the identification and structural determination of flavonoids. Its advantages are high sensitivity and possibilities of hyphenation with liquid chromatographic methods for the analysis of mixtures of compounds. Different desorption ionization methods allow the analysis of underivatized glycosides. Advances in mass spectrometry methodology have been shown to be extremely valuable for flavonoid analysis especially the use of mild ionization techniques, which have improved the possibility of recording molecular ions and suppressed the detection limits by several orders of magnitude. Detailed structural information can be obtained by resorting to cone voltage fragmentation and use of various types of mass analyzers. In this chapter, examples of the usefulness of mass spectroscopy techniques to the structural characterization of various flavonoids will be presented. In particular analysis of flavonoid aglycones and mono and di-O-glycosides, oligomeric and polymeric procyanidins using electropsray (ESI), matrix-assisted laser desorption ionization (MALDI), and tandem (MS/MS) mass spectrometry will be also presented.

Anti-HIV and immune modulating activities of IND02

Background A vaccine that prevents HIV infection should not only induce functional inhibitory, neutralizing antibodies, but also promote Fc-mediated inhibitory antibodies displaying ADCC or phagocytosis. The aim of this study is to analyze the effect of IND02, a cinnamon derived procyanidin polymer on the interaction of HIV-1 gp120 with its co-receptors as well as its adjuvant like activity along with HIV-specific antibodies.

Preparation, characterization, and induction of cell apoptosis of cocoa procyanidins–gelatin–chitosan nanoparticles

Cocoa procyanidins (CPs)–gelatin–chitosan nanoparticles were fabricated based on the procyanidin–protein and electrostatic interactions, with an objective to enhance the stability and bioactivity of CPs. The CPs were purified using chromatographic methods and analyzed using HPLC equipped with a fluorescence detector (FLD) and mass spectrometer (MS). The purified CPs had a purity of 53.1% (w/w) and contained procyanidin oligomers (from monomer to decamers) and polymers, with polymers being the predominant component (26.4%, w/w). Different CPs–gelatin–chitosan mass ratios were tested to investigate the effects of formulation on the nanoparticle fabrication. Using CPs–gelatin–chitosan mass ratio of 0.75:1:0.5, the resultant nanoparticles had a particle size of 344.7nm, zeta-potential of +29.8mV, particle yield of 51.4%, loading efficiency of 50.1%, and loading capacity of 20.5%. The CPs–gelatin–chitosan nanoparticles were spherical as observed by scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) suggested that the primary interaction between the CPs and gelatin was hydrogen bond and hydrophobic interaction, while electrostatic interaction was the main binding force between chitosan and CPs–gelatin nanoparticles. Nanoencapsulation of the CPs significantly improved the stability of the CPs at 60°C. The CPs–gelatin–chitosan nanoparticles showed the same apoptotic effects at lower concentrations in human acute monocytic leukemia THP-1 cells compared with the CPs in solution.

Antioxidant and Cytoprotective Effects of Oligomeric and Polymeric Procyanidin Fractions from Defatted Grape Seed in PC12 Cells

In this study, a crude polyphenol extract (CPE) from defatted grape seeds was evaluated for antioxidant and cytoprotective effects in PC12 cells. The CPE was then fractionated into a catechin and oligomeric procyanidin fraction (F(cat+olig)) and a polymeric procyanidin fraction (F(pol)), and the bioactivities of the fractions were evaluated individually. F(pol) was the richest in total polyphenol, total flavonoid, and polymeric procyanidin but contained less flavan-3-ol than F(cat+olig). Consistent with these results, F(pol) had the highest 2,2-diphenyl-β-picrylhydrazyl radical scavenging activity and reducing power. Both F(cat+olig) and F(pol) had higher 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic) acid radical scavenging activity than CPE. The resistance of PC12 cells against oxidative stress, after pretreatment with F(pol) (200 μg/mL) for 9 h, was 100.7±2.9% of that in the control. Moreover, pretreating these cells with F(cat+olig) and F(pol) significantly decreased reactive oxygen species generation. These results provide information on a potential new source of antioxidants in the form of a functional food derived from an agricultural by-product.

Bioactivity‐guided Fractionation of Phyllanthus orbicularis and Identification of the Principal Anti HSV‐2 Compounds

The antiherpes virus properties of Phyllanthus orbicularis Kunth, a Cuban-endemic medicinal plant, have been reported previously but data on its phytochemical profile and identification of antiviral metabolites as well as their mechanisms of action are still lacking. In this work, a bioactivity-guided phytochemical analysis was performed in order to isolate anti HSV-2 compounds. P. orbicularis contained mainly phenolic acids derivatives and flavonoids. The antiviral effects were attributed to (-)-epicatechin-3-O-gallate (EC(50) = 11.7 µg/mL), procyanidins B1 and B2 (EC(50) = 32.8 µg/mL and 24.2 µg/mL, respectively) as well as oligomeric and polymeric procyanidins and their gallate derivatives. The antiviral mechanisms of the active P. orbicularis extracts and fractions were also investigated and the inhibition of several HSV-2 early replication events and DNA synthesis were observed. This is the first study of extensive fractionation and phytochemical characterization of phenolic compounds from this species.

Characterization and Quantitation of Low and High Molecular Weight Phenolic Compounds in Apple Seeds

The phenolic constituents of seeds of 12 different apple cultivars were fractionated by sequential extraction with aqueous acetone (30:70, v/v) and ethyl acetate after hexane extraction of the lipids. Low molecular weight phenolic compounds were individually quantitated by RP-HPLC-DAD. The contents of extractable and nonextractable procyanidins were determined by applying RP-HPLC following thiolysis and n-butanol/HCl hydrolysis, respectively. As expected, the results revealed marked differences of the ethyl acetate extracts, aqueous acetone extracts, and insoluble residues with regard to contents and mean degrees of polymerization of procyanidins. Total phenolic contents in the defatted apple seed residues ranged between 18.4 and 99.8 mg/g. Phloridzin was the most abundant phenolic compound, representing 79-92% of monomeric polyphenols. Yields of phenolic compounds significantly differed among the cultivars under study, with seeds of cider apples generally being richer in phloridzin and catechins than seeds of dessert apple cultivars. This is the first study presenting comprehensive data on the contents of phenolic compounds in apple seeds comprising extractable and nonextractable procyanidins. Furthermore, the present work points out a strategy for the sustainable and complete exploitation of apple seeds as valuable agro-industrial byproducts, in particular as a rich source of phloridzin and antioxidant flavanols.

Procyanidin xylosides from the bark of Betula pendula

A procyanidin dimer xyloside, catechin-(4α→8)-7-O-β-xylopyranosyl-catechin, was isolated from the inner bark of Betula pendula and its structure was determined using 1D and 2D NMR, CD and high-resolution ESIMS. Interestingly, the 7-O-β-xylopyranose unit was found to be present in the lower terminal unit of the dimer. In addition to this procyanidin dimer xyloside, an entire series of oligomeric and polymeric procyanidin xylosides was detected. Their structures were investigated by hydrophilic interaction HPLC–HRESIMS. Procyanidin glycosides are still rarely found in nature.