Polyphenols Derived from Lychee Seed Suppress Aß (1-42)-Induced Neuroinflammation.

Amyloid-ß (Aß) is commonly recognized as the most important factor that results in neuronal cell death and accelerates the progression of Alzheimer's disease (AD). Increasing evidence suggests that microglia activated by Aß release an amount of neurotoxic inflammatory cytokines that contribute to neuron death and aggravate AD pathology. In our previous studies, we found that lychee seed fraction (LSF), an active fraction derived from the lychee seed, could significantly improve the cognitive function of AD rats and inhibit Aß-induced neuroinflammation in vitro, and decrease neuronal injuries in vivo and in vitro. In the current study, we aimed to isolate and identify the specific components in LSF that were responsible for the anti-neuroinflammation effect using preparative high performance liquid chromatography (pre-HPLC), liquid chromatography-mass spectrometry (LC-MS), and nuclear magnetic resonance (NMR) methods. To this end, we confirmed two polyphenols including catechin and procyanidin A2 that could improve the morphological status of BV-2 cells and suppress the release, mRNA levels, and protein expression of pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), and interleukin-6 (IL-6) through downregulating the nuclear factor-κB (NF-κB) signaling pathway using ELISA, RT-PCR, and Western blotting methods. Furthermore, catechin and procyanidin A2 could inhibit Aß-induced apoptosis in BV-2 cells by upregulating Bcl-2 and downregulating Bax protein expression. Therefore, the current study illustrated the active substances in lychee seed, and first reported that catechin and procyanidin A2 could suppress neuroinflammation in Aß-induced BV-2 cells, which provides detailed insights into the molecular mechanism of catechin and procyanidin A2 in the neuroprotective effect, and their further validations of anti-neuroinflammation in vivo is also essential in future research.

Procyanidin A2 Modulates IL-4-Induced CCL26 Production in Human Alveolar Epithelial Cells.

Allergic asthma is an inflammatory lung disease that is partly sustained by the chemokine eotaxin-3 (CCL26), which extends eosinophil migration into tissues long after allergen exposure. Modulation of CCL26 could represent a means to mitigate airway inflammation. Here we evaluated procyanidin A2 as a means of modulating CCL26 production and investigated interactions with the known inflammation modulator, Interferon γ (IFNγ). We used the human lung epithelial cell line A549 and optimized the conditions for inducing CCL26. Cells were exposed to a range of procyanidin A2 or IFNγ concentrations for varied lengths of time prior to an inflammatory insult of interleukin-4 (IL-4) for 24 h. An enzyme-linked immunosorbent assay was used to measure CCL26 production. Exposing cells to 5 µM procyanidin A2 (prior to IL-4) reduced CCL26 production by 35% compared with control. Greatest inhibition by procyanidin A2 was seen with a 2 h exposure prior to IL-4, whereas IFNγ inhibition was greatest at 24 h. Concomitant incubation of procyanidin A2 and IFNγ did not extend the inhibitory efficacy of procyanidin A2. These data provide evidence that procyanidin A2 can modulate IL-4-induced CCL26 production by A549 lung epithelial cells and that it does so in a manner that is different from IFNγ.

Gut Microbiota Composition Affects Procyanidin A2-Attenuated Atherosclerosis in ApoE-/- Mice by Modulating the Bioavailability of Its Microbial Metabolites.

Procyanidin A2 (PCA2) has been shown to improve lipid metabolism. However, it remains to know whether it can play a role in preventing atherosclerosis (AS) through gut microbiota. This study examined the effect of PCA2 on high fat diet (HFD)-induced AS in ApoE-/- mice with an intact and antibiotic-depleted microbiota. PCA2 administration for 12 weeks attenuated HFD-induced AS in ApoE-/- mice, evidenced by obviously alleviating the histological abnormalities of the aorta, lipid accumulation, oxidative stress, and inflammation, which were accompanied by downregulating the expression of vascular cell adhesion molecule-1 and intracellular adhesion molecule-1 and upregulating peroxisome proliferator-activated receptor gamma, cholesterol 7 alpha-hydroxylase, and ATP-binding cassette transporter A1. Moreover, PCA2 treatment reshaped the gut microbiota imbalance caused by HFD, especially reducing the ratio of Firmicutes/Bacteroidetes and increasing the abundance of Verrucomicrobia. However, antibiotic intervention almost offset the alleviation of AS by PCA2 and prevented the biotransformation of PCA2 by gut microbiota, thus resulting in a 2327.21-6.27-fold decrease in its microbial metabolites of plasma. There was a marked correlation among the microbiota composition, the bioavailability of PCA2-derived microbial metabolites, and AS indicators. The findings indicate that the gut microbiota robustly influences the bioavailability of microbial metabolites that may partially drive the AS resilience property of PCA2.

Potential Activity Mechanisms of Aesculus hippocastanum Bark: Antioxidant Effects in Chemical and Biological In Vitro Models.

The bark of Aesculus hippocastanum is an herbal remedy used in conditions connected with vascular insufficiency; however, there is a lack of data concerning its mechanisms of action. The present work is a preliminary investigation into some of the potential directions of the bark activity. The phytochemically (qualitative UHPLC-PDA-MS/MS and quantitative UHPLC-PDA assays) characterized extract and its four main constituents (esculin, fraxin, (‒)-epicatechin and procyanidin A2) were first evaluated in terms of their antioxidant capacity. All analytes demonstrated dose-dependent scavenging potential towards the most common in vivo oxidants, with particularly advantageous capacity of the extract and its flavan-3-ol constituents against peroxynitrite (3.37-13.26 mmol AA/g), hydroxyl radical (5.03-8.91 mmol AA/g) and superoxide radical (3.50-5.50 mmol AA/g). Moreover, even at low concentrations (1-5 µg/mL), they protected components of human plasma against oxidative damage inflicted by peroxynitrite, preventing oxidation of plasma protein thiols and diminishing the tyrosine nitration and lipid peroxidation. High efficiency of the analytes was also demonstrated in preventing the peroxynitrite-induced nitrative changes of fibrinogen (up to 80% inhibition for (‒)-epicatechin at 50 µg/mL), an important protein of coagulation cascade. Additionally, the extract and its constituents had, at most, moderate inhibitory activity towards platelet aggregation induced by ADP and only negligible influence on clotting times. The results show that, among the investigated properties, the antioxidant activity might, to the highest extent, be responsible for the bark efficacy in vascular disorders, thus supporting its application in those conditions; they also indicate the directions for future research that would allow for better understanding of the bark activity.

Clitoria ternatea L. petal bioactive compounds display antioxidant, antihemolytic and antihypertensive effects, inhibit α-amylase and α-glucosidase activities and reduce human LDL cholesterol and DNA induced oxidation.

The purpose of this study was to use a statistical approach to optimise the experimental conditions regarding the extraction of bioactive compounds, and to analyse the in vitro functional properties of crude lyophilized extracts (CLE) and partially purified (PPE) extracts of Clitoria ternatea petals. The results showed that the factors of temperature and time influenced the extraction of phenolic compounds, antioxidant activity and the physicochemical parameters. Simultaneous optimisation showed that the same levels of bioactive compounds were extracted when using temperatures from 11.7 to 68.3 °C and times from 8.47 to 51.12 min. Principal component analysis revealed the experimental conditions that provided the extraction producing the highest level of phenolic content (40 °C/30 min). The CLE showed antimicrobial activity; protective effect against hemolysis of erythrocytes; inhibition of α-amylase, α-glucosidase and angiotensin-I-converting (ACE-I) enzymes; and inhibition of lipid peroxidation. The CLE and PPE demonstrated oxygen radical absorption capacity; inhibition of DNA strand scission; inhibition of LDL cholesterol oxidation; intracellular antioxidant activity against reactive oxygen species (>100 µg/mL); and no cytotoxicity (IC50, GI50 and LC50 > 900 µg/mL) against A549, HCT8 and IMR90 cell lines.

Transport of Flavanolic Monomers and Procyanidin Dimer A2 across Human Adenocarcinoma Stomach Cells (MKN-28).

It has been proven that A-type procyanidins, containing an additional ether bond, compared to B-type procyanidins are also bioavailable in vitro and in vivo. However, their bioavailability and absorption in the gastrointestinal tract remain uncertain. In this study, a model of the human adenocarcinoma stomach cell line (MKN-28) was established to explore the cellular transport of flavanolic monomers and procyanidin dimer A2, which were isolated from the litchi pericarp extract. After the integrity and permeability of the cell monolayer were ensured by measurement of the transepithelial electrical resistance and the apparent permeability coefficient for Lucifer yellow, the transportation of procyanidins A2 and B2, (-)-epicatechin (EC), and (+)-catechin (CC) was studied at pH 3.0, 5.0, or 7.0 in the apical side, with compound concentrations of 0.05 and 0.1 mg/mL based on the cytotoxicity test. High-performance liquid chromatography and liquid chromatography-mass spectrometry analyses indicated that EC, CC, and A2 were transported in the MKN-28 cell line from 30 to 180 min, while B2 showed no transport. The maximal transport efficiencies of EC, CC, and A2 were 23 ± 0.81, 13.16 ± 1.53, and 16.41 ± 1.36%, respectively, existing at 120, 180, and 120 min of transportation. Laser scanning confocal microscopy analysis presented the dynamic transmission of EC, in accordance with the result of concentration determination, suggesting that the A-type procyanidins are possibly absorbed through the stomach barrier, which is pH- and time-dependent.

Procyanidin A2 in the Australian plant Alectryon oleifolius has anthelmintic activity against equine cyathostomins in vitro.

There is a need to investigate new methods of controlling cyathostomins in horses due to increasing anthelmintic resistance amongst these parasites. In a previous study we identified the Australian plant Alectryon oleifolius as having anthelmintic activity towards cyathostomins. This study aimed to isolate and identify the bioactive compound(s) responsible for all or part of this anthelmintic activity and quantify its activity in vitro. The condensed tannin procyanidin A2 was isolated from the plant through a process of bioassay guided fractionation and identified using 1D and 2D nuclear magnetic resonance spectroscopy and high performance liquid chromatography with mass spectrometry. Procyanidin A2 demonstrated significant anthelmintic activity in larval development assays, completely inhibiting development from egg to third larval stage at concentrations as low as 50µg/mL and having an IC50 value of 12.6µg/mL. Procyanidin A2 also significantly inhibited larval migration at concentrations of 25µg/mL. This study indicates that procyanidin A2 is the principal anthelmintic compound in extracts from A. oleifolius, and further highlights the potential for the use of this plant as a component of cyathostomin control programs in the future.

Inhibition of PDGF-BB-induced proliferation and migration in VSMCs by proanthocyanidin A2: Involvement of KDR and Jak-2/STAT-3/cPLA2 signaling pathways.

Proanthocyanidin A2 (PA2), one of A-type proanthocyanidins, has been shown to harbor a broad spectrum of pharmacological activities, including anti-inflammatory, antioxidant, anti-HIV, anti-CDV and anti-?-glucosidase activities. However, little is known about the role for PA2 in regulating PDGF-induced VSMC proliferation and migration. In the present study, we investigated the possible effects of PA2 on PDGF-BB-induced proliferation, migration and inflammation in VSMCs in vitro to mimic a postangioplasty PDGF shedding condition. Herein, the data clearly show that PA2 markedly inhibited proliferation, migration and inflammatory responses at 0-30??g/ml concentration in VSMCs in vitro. 10-30??g/ml PA2 inhibited PDGF-mediated NAD(P)H oxidase activation and intracellular ROS formation in VSMCs. Furthermore, the effects exerted by PA2 involve the participation of KDR and Jak-2/STAT-3/cPLA2 signaling pathways. These data also highlight the possible therapeutic use of PA2 in vascular proliferative diseases, where abnormal proliferation and migration play important pathological roles.

Synthesis and Evaluation of Antimicrobial and Antibiofilm Properties of A-Type Procyanidin Analogues against Resistant Bacteria in Food.

Natural A-type procyanidins have shown very interesting biological activities, such as their proven antiadherence properties against pathogenic bacteria. In order to find the structural features responsible for their activities, we describe herein the design and synthesis of six A-type procyanidin analogues and the evaluation of their antimicrobial and antibiofilm properties against 12 resistant bacteria, both Gram positive and Gram negative, isolated from organic foods. The natural A-type procyanidin A-2, which had known antiadherence activity, was also tested as a reference compound for the comparative studies. Within the series, analogue 4, which had a NO2 group on ring A, showed the highest antimicrobial activity (MIC of 10 µg/mL) and was one of the best molecules at preventing biofilm formation (up to 40% decreases at 100 µg/mL) and disrupting preformed biofilms (up to 40% reductions at 0.1 µg/mL). Structure-activity relationships are also analyzed.

Persimmon vinegar polyphenols protect against hydrogen peroxide-induced cellular oxidative stress via Nrf2 signalling pathway.

Since polyphenols are known to exhibit antioxidative properties, we prepared and characterized persimmon vinegar polyphenols (PVP) in this study. Furthermore, we investigated the protective effect of PVP on hydrogen peroxide (H2O2)-induced oxidative stress in HepG2 cells and its underlying mechanisms. Our results showed that flavon-3-ols were the predominant polyphenols in PVP. Pre-treatment with PVP significantly decreased (p < 0.05) H2O2-induced cell damage in a dose-dependent manner, accompanied by decrease in lactate dehydrogenase (LDH) leakage, aminotransferase activities, and ROS accumulation. Moreover, PVP upregulated the expression of antioxidative enzymes, such as heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQO1), and increased the levels of glutathione. Western blotting results showed that PVP induced the nuclear translocation of nuclear factor (erythroid-derived-2)-related factor 2 (Nrf2). Taken together, our results indicated that PVP effectively protected HepG2 cells against oxidative stress via activation of the Nrf2 antioxidative pathway.

Characterization of Date (Deglet Nour) Seed Free and Bound Polyphenols by High-Performance Liquid Chromatography-Mass Spectrometry.

Date (Pheonix dactylifera L.) seeds are a valuable and abundant by-product with various potential food applications. Free polyphenols (FPPs) and bound polyphenols (BPPs) of date seeds from Deglet Nour variety grown in Australia were investigated using high-performance liquid chromatography-mass spectrometry. The FPP fraction contained the following main phenolic compounds per gram of date seed powder; procyanidin B1 (499.8 ± 7.8 µg), procyanidin B2 (288.6 ± 6.1 µg), catechin (167.6 ± 2.1 µg), epicatechin (39.44 ± 0.39 µg), and protocatechuic acid (1.77 ± 0.22 µg). Additionally, one of the 2 A-type dimers was confirmed as procyanidin A2 (24.05 ± 0.12 µg/g). A-type dimers have not been reported before in date seeds. The BPP fraction contained epicatechin (52.59 ± 0.76 µg/g) and procyanidin B2 (294.2 ± 3.7 µg/g), while several peaks exhibiting ESI- m/z of 153 indicated dihydroxybenzoic acid isomers including protocatechuic acid (2.138 ± 0.025 µg/g). These findings contributed to our knowledge of date seed phytochemicals and understanding of their contribution to the reported bioactivities.

Procyanidin A2 and Its Degradation Products in Raw, Fermented, and Roasted Cocoa.

Cocoa is known as an important source of flavan-3-ols, but their fate "from the bean to the bar" is not yet clear. Here, procyanidin A2 found in native cocoa beans (9-13 mg/kg) appeared partially epimerized into A2E1 through fermentation, whereas a second epimer (A2E2) emerged after roasting. At m/z 575, dehydrodiepicatechin A was revealed to be the major HPLC peak before fermentation, whereas F1, a marker of well-conducted fermentations, becomes the most intense after roasting. RP-HPLC-ESI(-)-HRMS/MS analysis performed on a procyanidin A2 model medium after 12 h at 90 °C revealed many more degradation products than those identified in fermented cocoa, including the last epimer of A2, A2 open structure intermediates (m/z 577), and oxidized A-type dimers (m/z 573).

Simultaneous determination of epicatechin and procyanidin A2 markers in Litchi chinensis leaves by high-performance liquid chromatography

ABSTRACT The fruits of Litchi chinensis Sonn., Sapindaceae, are renowned for their biological activities. However, their leaves are poorly explored, although they represent an important source of vegetable raw material with biological properties as antioxidant, anti-inflammatory and antinociceptive. An HPLC method was developed and validated for the simultaneous quantification of epicatechin and procyanidin A2 in the leaf hydroethanolic extract of L. chinensis. The markers and other unidentified components were separated on a Luna Phenomenex C18 column (250 mm × 4.6 mm, 5 µm) with mobile phase composed of acetonitrile: water pH 3.0 (with sulfuric acid), in a gradient run; at 1.0 ml min-1, 30 ºC and 278 nm for detection. The method was linear over an epicatechin and procyanidin A2 concentration range of 10–100 µg ml-1. The Limit of Quantification for epicatechin and procyanidin A2 were 1.7 and 2 µg ml-1, respectively. The Relative Standard Deviation (%) values for markers (intra- and inter-day precision studies) were <4.0% and the accuracy was 100 ± 5%. The method was applied to ten samples collected in the state of Santa Catarina (Brazil), which showed 14.8–44.5 and 44.8–69.6 mg g-1 of epicatechin and procyanidin A2, respectively. The proposed method could be a valuable tool for quality assessment of L. chinenis leaves as well as their herbal derivatives.