Fractionation of apple procyanidins according to their degree of polymerization by normal-phase high-performance liquid chromatography

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.

Oral Administration of Apple Procyanidins Ameliorates Insulin Resistance via Suppression of Pro-Inflammatory Cytokine Expression in Liver of Diabetic ob/ob Mice

Procyanidins, the main ingredient of apple polyphenols, are known to possess antioxidative and anti-inflammatory effects associated closely with the pathophysiology of insulin resistance and type 2 diabetes. We investigated the effects of orally administered apple procyanidins (APCs) on glucose metabolism using diabetic ob/ob mice. We found no difference in body weight or body composition between mice treated with APCs and untreated mice. A 4 week oral administration of APCs containing water [0.5% (w/v)] ameliorated glucose tolerance, insulin resistance, and hepatic gluconeogenesis in ob/ob mice. APCs also suppressed the increase in the level of the pancreatic β-cell. Insulin-stimulated Akt phosphorylation was significantly enhanced; pro-inflammatory cytokine expression levels were significantly decreased, and c-Jun N-terminal kinase phosphorylation was downregulated in the liver of those mice treated with APCs. In conclusion, APCs ameliorate insulin resistance by improving hepatic insulin signaling through suppression of hepatic inflammation in ob/ob mice, which may be a mechanism with possible beneficial health effects of APCs in disturbed glucose metabolism.

Reversed-phase liquid chromatographic analysis of hydrophobic interaction between proanthocyanidins and a C8-alkyl compound in aqueous solution

Structural and physicochemical properties of oligomeric flavan-3-ols (proanthocyanidins) in aqueous solution were investigated by spectrometric and reversed-phase (RP) HPLC analyses. Circular dichroism and fluorescence spectra of (–)-epicatechin (EC) oligomers linked through C-4 to C-8 interflavan bonds showed that EC oligomers larger than dimers formed a stable secondary structure in water. These EC oligomers are water-soluble hydrophilic compounds, whereas the oligomers were strongly retained by a C8-alkyl stationary phase under conventional RP-HPLC conditions. In a further C8-HPLC study, the hydrophobic interaction between EC oligomers and 1-octanesulfonic acid sodium salt (OSA Na) added to the mobile phase was quantitatively evaluated based on the relationship between the logarithm of the retention factor of the solute and the OSA Na concentration in the mobile phase. The strength values of the hydrophobic interaction of EC oligomers larger than dimers were the highest of 22 tested polyphenolic standards.

Dual-Targeting Lactoferrin-Conjugated Polymerized Magnetic Polydiacetylene-Assembled Nanocarriers with Self-Responsive Fluorescence/Magnetic Resonance Imaging for In Vivo Brain Tumor Therapy

Maintaining a high concentration of therapeutic agents in the brain is difficult due to the restrictions of the blood-brain barrier (BBB) and rapid removal from blood circulation. To enable controlled drug release and enhance the blood-brain barrier (BBB)-crossing efficiency for brain tumor therapy, a new dual-targeting magnetic polydiacetylene nanocarriers (PDNCs) delivery system modified with lactoferrin (Lf) is developed. The PDNCs are synthesized using the ultraviolet (UV) cross-linkable 10,12-pentacosadiynoic acid (PCDA) monomers through spontaneous assembling onto the surface of superparamagnetic iron oxide (SPIO) nanoparticles to form micelles-polymerized structures. The results demonstrate that PDNCs will reduce the drug leakage and further control the drug release, and display self-responsive fluorescence upon intracellular uptake for cell trafficking and imaging-guided tumor treatment. The magnetic Lf-modified PDNCs with magnetic resonance imaging (MRI) and dual-targeting ability can enhance the transportation of the PDNCs across the BBB for tracking and targeting gliomas. An enhanced therapeutic efficiency can be obtained using Lf-Cur (Curcumin)-PDNCs by improving the retention time of the encapsulated Cur and producing fourfold higher Cur amounts in the brain compared to free Cur. Animal studies also confirm that Lf targeting and controlled release act synergistically to significantly suppress tumors in orthotopic brain-bearing rats.

Impact of extended maceration and regulated deficit irrigation (RDI) in Cabernet Sauvignon wines: characterization of proanthocyanidin distribution, anthocyanin extraction, and chromatic properties

The impact of extended maceration (EM) was studied in Cabernet Sauvignon grapes sourced from a vineyard subjected to four regulated deficit irrigation (RDI) treatments: (I) 100% replenishment of crop evapotranspiration (100% ETc), (II) 70% ETc, (III) 25% ETc until véraison, followed by 100% ETc until harvest, and IV) 25% ETc. Each vineyard replicate was made into wine with two replicates designated as controls (10-day skin contact) and two as extended maceration (EM, 30-day skin contact). The mean degree of polymerization (mDP), size distribution, concentration, and composition of wine proanthocyanidins (PAs) and monomeric flavan-3-ols of 90 fractions were characterized by preparative and analytical HPLC techniques. The maceration length imparted a larger effect on most chemical parameters. The RDI treatment had no effect on the extraction patterns of anthocyanins, PAs, and/or on the origin of the PAs extracted into the wines. Conversely, EM led to anthocyanin losses and increased PA extraction during maceration, with ~73% of seed-derived PAs. Accordingly, the concentration of monomeric flavan-3-ols, oligomeric (2 ≤ mDP < 5) and polymeric PAs (mDP ≥ 5) was higher in EM wines. The size distribution of the wines' PAs revealed two major peaks as a function of concentration at mDP 2 (22-27% of total PAs mass) and at mDP 6-7 (12-17% of total PAs mass) and was found to follow a non-normal Rayleigh-type distribution.

Inhibitory effect of rose hip (Rosa canina L.) on melanogenesis in mouse melanoma cells and on pigmentation in brown guinea pigs

The compounds present in rose hips exerting an inhibitory action against melanogenesis in B16 mouse melanoma cells were investigated by dividing an aqueous extract of rose hips (RE) into four fractions. The 50% ethanol eluate from a DIAION HP-20 column significantly reduced the production of melanin and was mainly composed of procyanidin glycosides. We also found that this 50% ethanol eluate reduced the intracellular tyrosinase activity and also had a direct inhibitory effect on tyrosinase obtained as a protein mixture from the melanoma cell lysate. We also investigated the effect of orally administering RE on skin pigmentation in brown guinea pigs, and found that the pigmentation was inhibited together with the tyrosinase activity in the skin. These data collectively suggest that proanthocyanidins from RE inhibited melanogenesis in mouse melanoma cells and guinea pig skin, and could be useful as a skin-whitening agent when taken orally.

Recent developments in the HPLC separation of phenolic compounds

Phenolic compounds represent a class of highly complex naturally occurring molecules that possess a range of beneficial health properties. As a result, considerable attention has been devoted to the analysis of phenolics in a variety of samples. HPLC is the workhorse method for phenolic separation. However, conventional HPLC methods provide insufficient resolving power when faced with the complexity of real-world phenolic fractions. This limitation has been traditionally circumvented by extensive sample fractionation, multiple analysis methods and/or selective detection strategies. On the other hand, there is an increasing demand for improved throughput and resolving power from the chromatographic methods used for phenolic analyses. Fortunately, during the last decade, a number of important technological advances in LC have demonstrated significant gains in terms of both speed and resolution. These include ultra high-pressure liquid chromatography (UHPLC), high-temperature liquid chromatography (HTLC), multi-dimensional separations as well as various new stationary phase chemistries and morphologies. In recent years, these technologies have also found increasing application for phenolic analysis. This review seeks to provide an updated overview of the application of recent advances in HPLC to phenolic separation, with the emphasis on how these methodologies can contribute to improve performance in HPLC analysis of phenolics.

Off-line comprehensive 2-dimensional hydrophilic interaction x reversed phase liquid chromatography analysis of procyanidins

The development of an off-line comprehensive 2-dimensional liquid chromatography (2-D-LC) method for the analysis of procyanidins is reported. In the first dimension, oligomeric procyanidins were separated according to molecular weight by hydrophilic interaction chromatography (HILIC), while reversed phase LC was employed in the second dimension to separate oligomers based on hydrophobicity. Fluorescence, UV and electrospray ionisation mass spectrometry (ESI-MS) were employed for identification purposes. The combination of these orthogonal separation methods is shown to represent a significant improvement compared to 1-dimensional methods for the analysis of complex high molecular weight procyanidin fractions, by simultaneously providing isomeric and molecular weight information. The low correlation (r(2)<0.2100) between the two LC modes afforded a practical peak capacity in excess of 2300 for the optimal off-line method. The applicability of the method is demonstrated for the analysis of phenolic extracts of apple and cocoa.

Separation and identification of polyphenols in apple pomace by high-speed counter-current chromatography and high-performance liquid chromatography coupled with mass spectrometry

Apple pomace, a by-product in the processing of apple juice, was investigated as a potential source of polyphenols. Two methods of separation and purification of polyphenols from apple pomace extract were established by combination of gel chromatography with high-speed counter-current chromatography (HSCCC) and solvent extraction with HSCCC, respectively. The optimal separation was performed on a Sephadex LH-20 column using gradient aqueous ethanol as eluting solvent from 0% to 100% in increments of 10%. HPLC analysis indicated that main polyphenols existed in fractions eluted between 40% and 50% aqueous ethanol. The fractions of interest from column were separated by HSCCC with the solvent system hexane-ethyl acetate-1% aqueous acetic acid (0.5:9.5:10, v/v/v). Ethyl acetate fractionation of the apple pomace extract followed by direct HSCCC separation by the same solvent system in the volume ratio of 1:9:10 also produced a good separation of the main polyphenols of interest. Six high-purity polyphenols were achieved tentatively and identified by HPLC/MS: chlorogenic acid (1, m/z 354), quercetin-3-glucoside/quercetin-3-glacaside (2, m/z 464), quercetin-3-xyloside (3, m/z 434), phloridzin (4, m/z 436), quercetin-3-arabinoside (5, m/z 434), and quercetin-3-rhamnoside (6, m/z 448). These results provided a preliminary foundation for further development and exploration of apple pomace.

Direct mass spectrometry approaches to characterize polyphenol composition of complex samples

Lower molecular weight polyphenols including proanthocyanidin oligomers can be analyzed after HPLC separation on either reversed-phase or normal phase columns. However, these techniques are time consuming and can have poor resolution as polymer chain length and structural diversity increase. The detection of higher molecular weight compounds, as well as the determination of molecular weight distributions, remain major challenges in polyphenol analysis. Approaches based on direct mass spectrometry (MS) analysis that are proposed to help overcome these problems are reviewed. Thus, direct flow injection electrospray ionization mass spectrometry analysis can be used to establish polyphenol fingerprints of complex extracts such as in wine. This technique enabled discrimination of samples on the basis of their phenolic (i.e. anthocyanin, phenolic acid and flavan-3-ol) compositions, but larger oligomers and polymers were poorly detectable. Detection of higher molecular weight proanthocyanidins was also restricted with matrix-assisted laser desorption ionization (MALDI) MS, suggesting that they are difficult to desorb as gas-phase ions. The mass distribution of polymeric fractions could, however, be determined by analyzing the mass distributions of bovine serum albumin/proanthocyanidin complexes using MALDI-TOF-MS.

Fractionation of polyphenol-enriched apple juice extracts to identify constituents with cancer chemopreventive potential

Apples and apple juices are widely consumed and rich sources of phytochemicals. The aim of the present study was to determine which apple constituents contribute to potential chemopreventive activities, using a bioactivity-directed approach. A polyphenol-enriched apple juice extract was fractionated by various techniques. Extract and fractions were tested in a series of test systems indicative of cancer preventive potential. These test systems measured antioxidant effects, modulation of carcinogen metabolism, anti-inflammatory and antihormonal activities, and antiproliferative potential. Regression analyses indicated that 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging potential correlated with the sum of low molecular weight (LMW) antioxidants (including chlorogenic acid, flavan-3-ols, and flavonols) and procyanidins, whereas peroxyl radicals were more effectively scavenged by LMW compounds than by procyanidins. Quercetin aglycone was identified as a potent Cyp1A inhibitor, whereas phloretin and (-)-epicatechin were the most potent cyclooxygenase 1 (Cox-1) inhibitors. Aromatase and Cyp1A inhibitory potential and cytotoxicity toward HCT116 colon cancer cells increased with increasing content in procyanidins. Overall, apple juice constituents belonging to different structural classes have distinct profiles of biological activity in these in vitro test systems. Since carcinogenesis is a complex process, combination of compounds with complementary activities may lead to enhanced preventive effects.

Rapid preparation of procyanidins B2 and C1 from Granny Smith apples by using low pressure column chromatography and identification of their oligomeric procyanidins

Research in the field of procyanidins is always hindered by the lack of procyanidin standards, and the preparation of procyanidins, especially in large scale, remains difficult and time-consuming. Commercial sources of procyanidin standards are scarce. In this study, a rapid preparation method of procyanidins by using low-pressure column chromatography was developed. Procyanidins in Granny Smith apples were extracted with boiled water and purified on an ADS-17 macroporous resin column to obtain a Granny Smith apple procyanidin extract (GSE). GSE was fractionated according to its degree of polymerization on a Toyopearl TSK HW-40s column. Procyanidins B2 (epicatechin-(4beta-8)-epicatechin) and C1 (epicatechin-(4beta-8)-epicatechin-(4beta-8)-epicatechin) were prepared without HPLC separation. Oligomeric procyanidins from Granny Smith apples were also identified by liquid chromatography-electrospray ionization-mass spectrometry.

Retention behavior of oligomeric proanthocyanidins in hydrophilic interaction chromatography

A novel method was developed for the separation of proanthocyanidins (PAs; oligomeric flavan-3-ols) by hydrophilic interaction chromatography (HILIC) using an amide-silica column eluting with an aqueous acetonitrile mobile phase. The best separation was achieved with a linear gradient elution of acetonitrile-water at ratios of 9:1 to 5:5 (v/v) for 60 min at a flow rate of 1.0 ml/min. Under these HPLC conditions, a mixture of natural oligomeric PAs (from apple) was separated according to degree of polymerization (DP) up to decamers. The DP of each separated oligomer was confirmed by LC/electrospray ionization MS. In further HILIC separation studies of 15 different flavan-3-ol and oligomeric PA (up to pentamer) standards with an isocratic elution of acetonitrile-water (84:16), a high correlation was observed between the logarithm of retention factors (log k) and the number of hydroxyl groups in their structures. The coefficient of this correlation (r2=0.9501) was larger than the coefficient (r2=0.7949) obtained from the correlation between log k and log P(o/w) values. These data reveal that two effects, i.e. hydrogen bonding between the carbamoyl terminal on the column and the hydroxyl group of solute oligomer and hydrophilicity based on the high-order structure of oligomeric PAs, corporately contribute to the separation, but the hydrogen bonding effect is predominant in our HILIC separation mode.

Isolation and structure elucidation of procyanidin oligomers from Saskatoon berries (Amelanchier alnifolia)

Proanthocyanidin oligomers with different degrees of polymerization were isolated from Saskatoon berries (Amelanchier alnifolia) by means of gel adsorption and normal-phase liquid chromatography. The proanthocyanidins were identified using electrospray ionization mass spectrometry, nuclear magnetic resonance spectroscopy, and thiolytic degradation coupled with reversed-phase liquid chromatography. The results established that Saskatoon berries contain proanthocyanidins from dimers through heptamers and higher polymers. Saskatoon proanthocyanidins are essentially of procyanidin type, consisting mainly of epicatechin units linked by B-type bonds. The simple procyanidin profile of Saskatoon berries allowed the procyanidins to be separated precisely according to their degrees of polymerization. In the future they can be used as standard compounds for qualitative and quantitative analysis of procyanidins as well as for elucidation of the biological activities of proanthocyanidins.

NMR, ESI/MS, and MALDI-TOF/MS analysis of pear juice polymeric proanthocyanidins with potent free radical scavenging activity

The structure of a polymeric proanthocyanidin fraction isolated from pear juice was characterized by NMR, ESI/MS, and MALDI-TOF/MS analyses, and its antioxidant activity was investigated using the DPPH free radical scavenging method. The results obtained from 13C NMR analysis showed the predominance of signals representative of procyanidins. Typical signals in the chemical shift region between 70 and 90 ppm demonstrated the exclusive presence of epicatechin units. The results obtained through negative ESI/MS analysis showed singly and doubly charged ions corresponding to the molecular mass of procyanidins with a degree of polymerization up to 22. The spectra obtained through MALDI-TOF/MS analysis revealed the presence of two series of tannin oligomers. Supporting the observations from NMR spectroscopy, the first series consists of well-resolved tannin identified as procyanidin polymers units with chain lengths of up to 25. A second series of monogalloyl flavan-3-ols polymers with polymerization degree up to 25 were also detected. This is the first mass spectrometric evidence confirming the existence of galloylated procyanidin oligomers in pear fruits. Within each of these oligomers, various signals exist suggesting the presence of several oligomeric tannins. The antioxidant properties of the polymeric fraction were investigated through reduction of the DPPH free radical, and the results obtained showed that the polymeric fraction exhibited a higher antioxidant power compared to those of (+)-catechin and B3 procyanidin dimer.

Phenolics in cereals, fruits and vegetables: Occurrence, extraction and analysis

Consumption of plant foods, particularly fruits, vegetables and cereal grains is encouraged because they render beneficial health effects. Phenolics and polyphenolics are among the most desirable food bioactives because of their antioxidant activity, brought about by a number of pathways, or due to other mechanisms. The analysis of phenolics and polyphenolics requires their extraction possible purification and structure elucidation. This overview provides a cursory account of the source, extraction and analysis of phenolics in fruits, vegetables and cereals.

High-performance liquid chromatography separation and purification of cacao (Theobroma cacao L.) procyanidins according to degree of polymerization using a diol stationary phase

A new chromatographic approach for separating cacao procyanidins according to their degree of polymerization has been developed. It utilizes diol stationary phase columns operating in normal phase mode with a binary gradient of acidified acetonitrile and methanol-water. Performance of the diol stationary phase was evaluated on an analytical scale utilizing classical chromatographic conditions for the normal phase separation of procyanidins according to their degree of polymerization. The new separation approach was developed on an analytical scale but further extended to the preparative scale. These newly developed analytical and preparative high-performance liquid chromatography procedures were successfully applied to the separation, as well as isolation, of cacao procyanidins from unfermented cacao seeds. The degree of polymerization associated with each molecular weight fraction was determined by mass spectrometry.

Investigation of the topical application of procyanidin oligomers from apples to identify their potential use as a hair-growing agent

BACKGROUND

Procyanidins are a family of condensed tannins, which have been shown to possess hair-growing activity in both the in vitro and in vivo murine models.

AIMS

We report a 12-month clinical study aimed at treating male pattern baldness by external application of 0.7% apple procyanidin oligomers.

PATIENTS/METHODS

A double-blind clinical test involving a total of 43 subjects was performed. Twenty-one men in the procyanidin group and 22 men in the placebo control group were subjected to analysis. In the first 6 months, we compared the procyanidin and the placebo groups to assess the medicinal effects of procyanidin oligomers. The application time of the procyanidin group was subsequently extended to 12 months, and the time course of its remedial value was examined.

RESULTS

The increase in total number of hairs in a designated scalp area of the procyanidin group subjects after the 6-month trial was significantly greater than that of the placebo control group subjects (procyanidin, 3.3 +/- 13.0 (mean +/- SD)/0.50 cm(2); placebo, -3.6 +/- 8.1/0.50 cm(2); P < 0.001, two-sample t-test). Time course-dependent improvement in hair density was observed in the procyanidin subjects. No adverse side effects were observed in any of the subjects. Procyanidin therapy thus shows potential hair-growing activity.

Apple (Malus pumila) procyanidins fractionated according to the degree of polymerization using normal-phase chromatography and characterized by HPLC-ESI/MS and MALDI-TOF/MS

Our previously reported method for the fractionation of apple procyanidins was modified successfully to achieve the separation of (epi)catechins and procyanidins (ranging from dimers to octamers) according to the degree of polymerization. Normal-phase chromatography was employed, using a hexane-methanol-ethyl acetate mixture as the mobile phase. Each fraction was characterized using high-performance liquid-chromatography electrospray-ionization mass spectrometry (HPLC-ESI/MS) and matrix-assisted laser-desorption ionization time-of-flight mass spectrometry (MALDI-TOF/MS). This method will be useful for the evaluation of the physiological functions of proanthocyanidins and for the elucidation of their individual structures.

Procyanidin trimers to pentamers fractionated from apple inhibit melanogenesis in B16 mouse melanoma cells

The effects of apple polyphenols on melanogenesis in B16 mouse melanoma cells were investigated. The inhibitory effect of apple polyphenols was stronger than that of arbutin or kojic acid. Three polyphenol fractions (phenolic acid derivatives, procyanidins and other flavonoids) were isolated, and the procyanidins were fractionated according to the degree of polymerization using normal-phase chromatography. The procyanidin trimer-to-pentamer fractions were found to have the most pronounced effect on melanogenesis. Furthermore, each procyanidin fraction inhibited mushroom tyrosinase. No correlation between the degree of procyanidin polymerization and tyrosinase inhibitory activity was observed. Nevertheless, these observations suggest that procyanidins are effective inhibitors of tyrosinase.

Differential Activities of Plant Polyphenols on the Binding and Internalization of Cholera Toxin in Vero Cells

Plant polyphenols, RG-tannin, and applephenon had been reported to inhibit cholera toxin (CT) ADP-ribosyltransferase activity and CT-induced fluid accumulation in mouse ileal loops. A high molecular weight fraction of hop bract extract (HBT) also inhibited CT ADP-ribosyltransferase activity. We report here the effect of those polyphenols on the binding and entry of CT into Vero cells. Binding of CT to Vero cells or to ganglioside GM1, a CT receptor, was inhibited in a concentration-dependent manner by HBT and applephenon but not RG-tannin. These observations were confirmed by fluorescence microscopy using Cy3-labeled CT. Following toxin binding to cells, applephenon, HBT, and RG-tannin suppressed its internalization. HBT or applephenon precipitated CT, CTA, and CTB from solution, creating aggregates larger than 250 kDa. In contrast, RG-tannin precipitated CT poorly; it formed complexes with CT, CTA, or CTB, which were demonstrated with sucrose density gradient centrifugation and molecular weight exclusion filters. In agreement, CTA blocked the inhibition of CT internalization by RG-tannin. These data suggest that some plant polyphenols, similar to applephenon and HBT, bind CT, forming large aggregates in solution or, perhaps, on the cell surface and thereby suppress CT binding and internalization. In contrast, RG-tannin binding to CT did not interfere with its binding to Vero cells or GM1, but it did inhibit internalization.

Quantitation of polyphenols in different apple varieties

Forty-one apple samples, representing eight of the most widely cultivated varieties in western Europe, were collected in Trentino, Italy. Samples were extracted from fresh fruit with a mixture of acetone/water to achieve a good extraction of polyphenols, including proanthocyanidin oligomers which were analyzed by normal-phase HPLC. Up to 20 compounds including catechin, epicatechin, B2 procyanidin, hydroxycinnamates, flavonols, anthocyanins, and dihydrochalcones were analyzed by reversed-phase HPLC and LC-MS. Total polyphenol content was independently measured with an optimized Folin-Ciocalteu assay. The mean content of total polyphenols lay between 66.2 and 211.9 mg/100 g of FW depending on the variety. With chromatographic analysis, it was possible to explain the whole amount of total polyphenols measured by the FC assay. Flavanols (catechin and proanthocyanidins) are the major class of apple polyphenols (71-90%), followed by hydroxycinnamates (4-18%), flavonols (1-11%), dihydrochalcones (2-6%), and in red apples anthocyanins (1-3%).

The toxicology and safety of apple polyphenol extract

Apple polyphenol extract has strong antioxidant activity and various physiological functions, and is used in Japan as a food additive and nutritional supplements. Here, we tested the consumption safety of Applephenon, which is a polyphenol extract produced from unripe apples. The Ames test without S9 mixture revealed that Applephenon, had slight mutagenicity at a high concentration of 2500 microg/plate; however, both chromosomal aberration test and the micronucleus test found no significant mutagenicity. Furthermore, an acute oral-toxicity test, and a 90-day subchronic-toxicity test showed no significant hematological, clinical, chemical, histopathological, or urinary effects at a dose of 2000 mg/kg. These results confirm that Applephenon is safe and no toxic at average dietary level.

Separation of proanthocyanidins by degree of polymerization by means of size-exclusion chromatography and related techniques

The molecular masses of polyphenols in plants and food vary greatly up to the order of 10 kDa. Polymerized polyphenols are not only natural antioxidants but also strong inhibitors of numerous physiological enzymatic activities. Several useful methods for the determination and separation of these high-molecular-mass polyphenols have recently been developed. In this review, details of the methods and applications of size-exclusion chromatographic separation of polymerized polyphenols, particularly those of proanthocyanidins, are described and compared with other related chromatographic or mass spectrometric analyses.

Isolation and structural elucidation of some procyanidins from apple by low-temperature nuclear magnetic resonance

Procyanidin fractions from apple were separated according to the degree of polymerization using normal phase chromatography. Evaluation of physiological functionalities of procyanidins requires individual structural determination. However, it is difficult to elucidate the structure of procyanidins, in particular those with (+)-epicatechin (1) or (-)-catechin (2) units, and determine whether the interflavanoid bonds are 4beta-->8 or 4beta-->6 without cleavage and acetylation. Structural determination used LC-MS and low-temperature NMR. Nine procyanidins were separated by preparative HPLC consisting of three well-known procyanidins [procyanidin B1 (3), procyanidin B2 (4), and procyanidin C1 (5)] and six new procyanidins [epicatechin-(4beta-->8)-epicatechin-(4beta-->8)-catechin (6); epicatechin-(4beta-->6)-epicatechin-(4beta-->8)-catechin (7); epicatechin-(4beta-->6)-epicatechin-(4beta-->8)-epicatechin (8); epicatechin-(4beta-->8)-epicatechin-(4beta-->6)-catechin (9); epicatechin-(4beta-->8)-epicatechin-(4beta-->6)-epicatechin (10); and epicatechin-(4beta-->8)-epicatechin-(4beta-->8)-epicatechin-(4beta-->8)-epicatechin (11)]. Compounds 6-11 were detected for the first time as apple constituents.

Sample handling strategies for the determination of biophenols in food and plants

The analysis of phenols in samples of plant and food origin attracts considerable attention. However, sample handling is often an ignored feature of the analysis. This review highlights the importance of sample extraction in an analysis and the problems that can arise during this step. Many questions remain unanswered and there is a need to more carefully validate extraction efficiencies. Although many new procedures have been developed the use of traditional techniques still dominates.

Characterization of polymerized polyphenols by size-exclusion HPLC

Various kinds of high-molecular-mass polyphenols such as condensed tannins, hydrolyzable tannins, and polymerized anthocyanins, were readily characterized by a new size-exclusion HPLC method. This rapid analytical method may also be useful for the profiling of molecular mass distribution of polyphenolic constituents in many kinds of food materials.

Isolation and identification of oligomeric procyanidins from Crataegus leaves and flowers

Oligomeric procyanidins were isolated from the leaves and flowers of hawthorn (Crataegus laevigata). A trimer, epicatechin-(4 beta-->8)-epicatechin-(4 beta-->6)-epicatechin, and a pentamer consisting of (-)-epicatechin units linked through C-4 beta/C-8 bonds have been isolated from hawthorn for the first time, in addition to known procyanidins including dimers B-2, B-4 and B-5, trimers C-1 and epicatechin-(4 beta-->6)-epicatechin-(4 beta-->8)-epicatechin, and tetramer D-1. A fraction containing a hexamer was also found.

Composition of phenolic compounds in a Portuguese pear (Pyrus communis L. var. S. Bartolomeu) and changes after sun-drying

The composition of phenolic compounds of a Portuguese pear cultivar (Pyrus communis L. var. S. Bartolomeu) was determined by HPLC after thioacidolysis. The average concentration of phenolic compounds in pear harvested at commercial maturity stage was 3.7 g per kg of fresh pulp. Procyanidins were the predominant phenolics (96%), with a mean degree of polymerization (mDP) of 13-44; hydroxycinnamic acids (2%), arbutin (0.8%), and catechins (0.7%) were also present. The most abundant monomer in the procyanidin structures was (-)-epicatechin (99%), which was found as extension and terminal units; (+)-catechin (1%) was found only as a terminal unit. Sun-drying of these pears caused a decrease of 64% (on a dry pulp basis) in the total amount of native phenolic compounds. Hydroxycinnamic acids and procyanidins showed the largest decrease; the B2 procyanidin was not found at all in the sun-dried pear. Less affected were arbutin and catechins. In the sun-dried pear, the procyanidins with high mDP became unextractable in the solvents used.

Separation of apple procyanidins into different degrees of polymerization by high-speed counter-current chromatography

Apple procyanidins were fractionated by high-speed counter-current chromatography in a one-step operation from apple condensed tannins using a type-J multilayer coil planet centrifuge. The separation of procyanidins was performed with a two-phase solvent system composed of methyl acetate-water (1:1) by eluting the upper phase at a flow-rate of 1.0 ml/min. Each fraction was examined by time-of-flight mass spectrometry. Procyanidins were separated according to their degrees of polymerization.

Investigation of topical application of procyanidin B-2 from apple to identify its potential use as a hair growing agent

Procyanidin B-2 is a polyphenol compound we have identified in apple which acts as a hair-growing factor in the murine model both in vitro and in vivo. This report describes our investigation of the effects of 1% procyanidin B-2 tonic on human hair growth after sequential use for 6 months. A double-blind clinical test involving a total of 29 subjects was performed. Nineteen men in the procyanidin B-2 group and 10 men in the placebo control group were subjected to analyses. No adverse side effects were observed in either group. The hair-growing effect was evaluated using a macrophotography technique combined with measurements of the hair diameter of clipped hairs. The increase in number of total hairs in the designated scalp area (0.5 cm square = 0.25 cm2 area) of procyanidin B-2 group subjects after the 6-month trial was significantly greater than that of the placebo control group subjects (procyanidin B-2, 6.68 +/- 5.53 (mean +/- SD)/0.25 cm2; placebo, 0.08 +/- 4.56 (mean +/- SD)/0.25 cm2; P < 0.005, two-sample t test). The increase in number of terminal hairs, which are defined as hairs more than 60 microm in diameter, in the designated area (0.5 cm square = 0.25 cm2 area) of the procyanidin B-2 group subjects after the 6-month trial was significantly greater than that of the placebo control group subjects (procyanidin B-2, 1.99 +/- 2.58 (mean +/- SD)/0.25 cm2; placebo, -0.82 +/- 3.40 (mean +/- SD)/0.25 cm2; P < 0.02, two-sample t test). Procyanidin B-2 therapy shows potential as a safe and promising cure for male pattern baldness.

Inhibitory effects of apple polyphenols and related compounds on cariogenic factors of mutans streptococci

The inhibitory effects of apple polyphenols (APP) on the synthesis of water-insoluble glucans by glucosyltransferases (GTF) of streptococci of the mutans group and on the sucrose-dependent adherence of the bacterial cells were examined in vitro. APP markedly inhibited the activity of GTF purified from the cariogenic bacterial cells. However, APP showed no significant effect on the growth of the cariogenic bacteria. The strongest GTF inhibitors in APP were apple condensed tannins (ACT), a mixture of procyanidins. The 50% inhibitory doses of ACT against the GTF of S. sobrinus and that of S. mutans were 1.5 microgram/mL and 5 microgram/mL, respectively. The ACT efficacy largely depended upon the degree of polymerization. Interestingly, while the other polyphenols known to inhibit GTF such as tannic acid markedly inhibited salivary alpha-amylase activity, APP and ACT only scarcely inhibited that enzyme activity. This means that APP and ACT might selectively inhibit the bacterial GTF activity under oral conditions.