Structure-function analysis of purified proanthocyanidins reveals a role for polymer size in suppressing inflammatory responses

Conformational preferences of cocoa oligomeric proanthocyanidins and their influence on polarity

Proanthocyanidins (OPACs) are the second largest class of plant metabolites after lignans. Although knowledge of their 3D conformations would add greatly to our understanding of their biological properties, very little has been published on the conformations of OPACs with a degree of polymerization (DP) above 4. We investigated the conformations of the linear epicatechin oligomers, prominent representatives of OPACs prevalent in apples and cocoa, where the epicatechin units are interconnected through the 4β-8 bonds. For DP-2 to DP-10 oligomers, conformational preferences reflected in the arrangement of consecutive flavan-3-ol units, are characterized by the φ torsion. For dimers, there are two energy wells corresponding to two preferred φ torsions, designated as compact and extended form. This behaviour is preserved in OPACs with higher DPs, but the most energetically favoured conformations are a combination of both, with compact-only or extended-only conformations being very unlikely. Thus, oligomers with DP ≥ 7 tend to assume an overall conformation approximating a spherical shape. This shape has a significant influence on the polarity of the OPAC oligomers expressed as 3D polar surface area, calculated using Spartan software for geometry-optimized 3D models, and possibly on other physicochemical properties. The results of polarity calculations provide a molecular-level rationale for the polarity-based chromatographic separation of the cocoa B-type procyanidins with DP range 4 to 10. In our experiments, using centrifugal partition chromatography (CPC) (a solvent system consisting of EtOAc-EtOH-water (6:1:5) v/v/v with aqueous phase stationary and upper phase mobile) we found that an enriched mixture of proanthocyanidins eluted first DP-1 (epicatechin) followed by consecutive elution of the DP-2 to DP-10 in the linear 4β-8 form. We demonstrated that such separation would not be possible if compact-only or extended-only conformations were present in solution. However, for the energy-favoured, spherically shaped conformations, the observed CPC elution order is fully justified.

A facile Immunoregulatory Constructional Design by Proanthocyanidin Optimizing Directional Chitosan Microchannel

Improving the interconnected structure and bioregulatory function of natural chitosan is beneficial for optimizing its performance in bone regeneration. Here, a facile immunoregulatory constructional design is proposed for developing instructive chitosan by directional freezing and alkaline salting out. The molecular dynamics simulation confirmed the assembly kinetics and structural features of various polyphenols and chitosan molecules. Along with the in vitro anti-inflammatory, antioxidative, promoting bone mesenchymal stem cell (BMSC) adhesion and proliferation performance, proanthocyanidin optimizing chitosan (ChiO) scaffold presented an optimal immunoregulatory structure with the directional microchannel. Transcriptome analysis in vitro further revealed the cytoskeleton- and immune-regulation effect of ChiO are the key mechanism of action on BMSC. The rabbit cranial defect model (Φ = 10 mm) after 12 weeks of implantation confirmed the significantly enhanced bone reconstitution. This facile immunoregulatory directional microchannel design provides effective guidance for developing inducible chitosan scaffolds.

Anti-inflammatory effect of proanthocyanidins from blueberry through NF-κβ/NLRP3 signaling pathway in vivo and in vitro

BACKGROUND

Systemic inflammatory response syndrome (SIRS) is an uncontrolled systemic inflammatory response. Proanthocyanidins (PC) is a general term of polyphenol compounds widely existed in blueberry fruits and can treat inflammation-related diseases. This study aimed to explore the regulatory effect of PC on lipopolysaccharide (LPS)-induced systemic inflammation and its potential mechanism, providing effective strategies for the further development of PC.

METHODS

Here, RAW264.7 macrophages were stimulated with LPS to establish an inflammation model in vitro, while endotoxin shock mouse models were constructed by LPS in vivo. The function of PC was investigated by MTT, ELISA kits, H&E staining, immunohistochemistry, and Western blot analysis.

RESULTS

Functionally, PC could demonstrate the potential to mitigate mortality in mice with endotoxin shock, as well as attenuated the levels of inflammatory cytokines (IL-6, TNF-α) and biochemical indicators (AST, ALT, CRE and BUN). Moreover, it had a significant protective effect on lung and kidney tissues damage. Mechanistically, PC exerted anti-inflammatory effects by inhibiting the activation of the NF-κB/NLRP3 signaling pathway.

CONCLUSION

PC might have the potential ability of anti-inflammatory effects via modulation of the NF-κB/NLRP3 signaling pathway.

Research progress of procyanidins in repairing cartilage injury after anterior cruciate ligament tear

Anterior cruciate ligament (ACL) tear is a common sports-related injury, and cartilage injury always emerges as a serious complication following ACL tear, significantly impacting the physical and psychological well-being of affected individuals. Over the years, efforts have been directed toward finding strategies to repair cartilage injury after ACL tear. In recent times, procyanidins, known for their anti-inflammatory and antioxidant properties, have emerged as potential key players in addressing this concern. This article focuses on summarizing the research progress of procyanidins in repairing cartilage injury after ACL tear. It covers the roles, mechanisms, and clinical significance of procyanidins in repairing cartilage injury following ACL tear and explores the future prospects of procyanidins in this domain. This review provides novel insights and hope for the repair of cartilage injury following ACL tear.

Gut microbiota-mediated polyphenol metabolism is restrained by parasitic whipworm infection and associated with altered immune function in mice

Polyphenols are phytochemicals commonly found in plant-based diets which have demonstrated immunomodulatory and anti-inflammatory properties. However, the interplay between polyphenols and pathogens at mucosal barrier surfaces has not yet been elucidated in detail. Here, we show that proanthocyanidin (PAC) polyphenols interact with gut parasites to influence immune function and gut microbial-derived metabolites in mice. PAC intake inhibited mastocytosis during infection with the small intestinal roundworm Heligmosomoides polygyrus, and altered the host tissue transcriptome at the site of infection with the large intestinal whipworm Trichuris muris, with a notable enhancement of type-1 inflammatory and interferon-driven gene pathways. In the absence of infection, PAC intake promoted the expansion of Turicibacter within the gut microbiota, increased fecal short chain fatty acids, and enriched phenolic metabolites such as phenyl-γ-valerolactones in the cecum. However, these putatively beneficial effects were reduced in PAC-fed mice infected with T. muris, suggesting concomitant parasite infection can attenuate gut microbial-mediated PAC catabolism. Collectively, our results suggest an inter-relationship between a phytonutrient and infection, whereby PAC may augment parasite-induced inflammation (most prominently with the cecum dwelling T. muris), and infection may abrogate the beneficial effects of health-promoting phytochemicals.

Antiglycation potential of metal ions and polyphenolic extract of chickpea on thiol-protease inhibitor: A management for diabetic complications

Glycation is the non-enzymatic adduct formation between reducing sugars or dicarbonyls with proteins and is a crucial molecular event under hyperglycaemic conditions of diabetes. The accumulation of advanced glycation end products (AGEs) due to glycation of proteins has been implicated in several diseases associated with ageing and diabetes. Thus, investigating the antiglycation potential of some trace metal ions (Manganese; Mn2+, and Zinc; Zn2+) and polyphenolic extract of chickpea seeds (PEC) on the methylglyoxal (MGO) induced glycation of a phytocystatin isolated from chickpea was taken up to find an inexpensive and non-toxic therapeutic means of medicating protein glycation and associated diabetic complications. The current study focused on the comparative analyses of these micronutrients and herbal extracts in inhibiting protein glycation and AGEs formation in a quest to develop nutraceuticals for managing diabetes. The effect of metals (Mn2+, Zn2+) and PEC on protein glycation was assessed by different techniques, i.e., glycation-specific AGE fluorescence and absorbance, thiol protease inhibitory activity assay, and conformational alterations by spectroscopic assays. This study revealed the significant anti-glycation potencies of Mn2+, Zn2+, and PEC against the MGO-induced glycation of CPC, which might pave the way for resolving pathological complications of diabetes by combining higher levels of efficacy, selectivity, and safety in humans. Moreover, characterization and identification of different AGEs formed during the glycation process in diabetics was done to apply the same for determining the onset of glycation at the early stage so that appropriate steps be taken to address the menace of diabetic complications.

Structural Similarities and Overlapping Activities among Dihydroflavonol 4-Reductase, Flavanone 4-Reductase, and Anthocyanidin Reductase Offer Metabolic Flexibility in the Flavonoid Pathway

Flavonoids are potent antioxidants that play a role in defense against pathogens, UV-radiation, and the detoxification of reactive oxygen species. Dihydroflavonol 4-reductase (DFR) and flavanone 4-reductase (FNR) reduce dihydroflavonols and flavanones, respectively, using NAD(P)H to produce flavan-(3)-4-(di)ols in flavonoid biosynthesis. Anthocyanidin reductase (ANR) reduces anthocyanidins to flavan-3-ols. In addition to their sequences, the 3D structures of recombinant DFR, FNR and ANR from sorghum and switchgrass showed a high level of similarity. The catalytic mechanism, substrate-specificity and key residues of three reductases were deduced from crystal structures, site-directed mutagenesis, molecular docking, kinetics, and thermodynamic ana-lyses. Although DFR displayed its highest activity against dihydroflavonols, it also showed activity against flavanones and anthocyanidins. It was inhibited by the flavonol quercetin and high concentrations of dihydroflavonols/flavonones. SbFNR1 and SbFNR2 did not show any activity against dihydroflavonols. However, SbFNR1 displayed activity against flavanones and ANR activity against two anthocyanidins, cyanidin and pelargonidin. Therefore, SbFNR1 and SbFNR2 could be specific ANR isozymes without delphinidin activity. Sorghum has high concentrations of 3-deoxyanthocyanidins in vivo, supporting the observed high activity of SbDFR against flavonols. Mining of expression data indicated substantial induction of these three reductase genes in both switchgrass and sorghum in response to biotic stress. Key signature sequences for proper DFR/ANR classification are proposed and could form the basis for future metabolic engineering of flavonoid metabolism.

Engineering Antioxidant Surfaces for Titanium-Based Metallic Biomaterials

Prolonged inflammation induced by orthopedic metallic implants can critically affect the success rates, which can even lead to aseptic loosening and consequent implant failure. In the case of adverse clinical conditions involving osteoporosis, orthopedic trauma and implant corrosion-wear in peri-implant region, the reactive oxygen species (ROS) activity is enhanced which leads to increased oxidative stress. Metallic implant materials (such as titanium and its alloys) can induce increased amount of ROS, thereby critically influencing the healing process. This will consequently affect the bone remodeling process and increase healing time. The current review explores the ROS generation aspects associated with Ti-based metallic biomaterials and the various surface modification strategies developed specifically to improve antioxidant aspects of Ti surfaces. The initial part of this review explores the ROS generation associated with Ti implant materials and the associated ROS metabolism resulting in the formation of superoxide anion, hydroxyl radical and hydrogen peroxide radicals. This is followed by a comprehensive overview of various organic and inorganic coatings/materials for effective antioxidant surfaces and outlook in this research direction. Overall, this review highlights the critical need to consider the aspects of ROS generation as well as oxidative stress while designing an implant material and its effective surface engineering.

Oligomeric Proanthocyanidins: An Updated Review of Their Natural Sources, Synthesis, and Potentials

Oligomeric Proanthocyanidins (OPCs), as a class of compounds widely found in plants, are particularly abundant in grapes and blueberries. It is a polymer comprising many different monomers, such as catechins and epicatechins. The monomers are usually linked to each other by two types of links, A-linkages (C-O-C) and B-linkages (C-C), to form the polymers. Numerous studies have shown that compared to high polymeric procyanidins, OPCs exhibit antioxidant properties due to the presence of multiple hydroxyl groups. This review describes the molecular structure and natural source of OPCs, their general synthesis pathway in plants, their antioxidant capacity, and potential applications, especially the anti-inflammatory, anti-aging, cardiovascular disease prevention, and antineoplastic functions. Currently, OPCs have attracted much attention, being non-toxic and natural antioxidants of plant origin that scavenge free radicals from the human body. This review would provide some references for further research on the biological functions of OPCs and their application in various fields.

Phenolic Acid-Amino Acid Adducts Exert Distinct Immunomodulatory Effects in Macrophages Compared to Parent Phenolic Acids

Caffeic acid (CA) and chlorogenic acid (CGA) are commonly found phenolic acids in plant-derived foods and beverages. Their corresponding adducts with cysteine (Cys) have been detected in coffee-containing beverages. However, despite the well-documented antioxidant and anti-inflammatory activity of CA and CGA, the immunomodulatory activities of the Cys adducts (CA-Cys and CGA-Cys) are unknown. The adducts were therefore synthesized, and their immunomodulatory effects were studied in lipopolysaccharide (LPS)-treated RAW 264.7 cells and compared to the activity of the parent phenolic acids. CA and CGA generally down-regulated the inflammatory responses. However, RNA-sequencing showed that the LPS-induced pathways related to Toll-like receptor signaling, chemokine signaling, and NOD-like receptor signaling, and JAK-STAT/MAPK signaling pathways were upregulated in adduct-treated cells relative to parent phenolic acids, while neurodegenerative disorder-related pathways and metabolic pathways were downregulated. Production of prostaglandin E₂ (PGE₂), interleukin-6, tumor necrosis factor-α (TNF-α), and reactive oxygen species (ROS) was all inhibited by CA and CGA (P < 0.05). PGE₂ and TNF-α were further suppressed in adduct-stimulated cells (P < 0.05), but ROS production was increased. For example, TNF-α produced by 100 μM CGA-stimulated cells and 100 μM CGA-Cys adduct-stimulated cells were 4.46 ± 0.23 and 1.61 ± 0.18 ng/mL, respectively. Thus, the addition of the Cys moiety drastically alters the anti-inflammatory activity of phenolic compounds.

Anti-Inflammatory, Anti-Bacterial, and Anti-Fungal Activity of Oligomeric Proanthocyanidins and Extracts Obtained from Lignocellulosic Agricultural Waste

It has now been proven that many pathogens that cause infections and inflammation gradually mutate and become resistant to antibiotics. Chemically synthesized drugs treating inflammation most often only affect symptoms, but side effects could lead to the failure of human organs' functionality. On the other hand, plant-derived natural compounds have a long-term healing effect. It was shown that sea buckthorn (SBT) twigs are a rich source of biologically active compounds, including oligomeric proanthocyanidins (PACs). This study aimed to assess the anti-pathogenic and anti-inflammatory activity of water/ethanol extracts and PACs obtained from the lignocellulosic biomass of eight SBT cultivars. The anti-pathogenic activity of extracts and PACs was studied against pathogenic bacteria Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Bacillus cereus and fungus Candida albicans in 96-well plates by the two-fold serial broth microdilution method. The anti-bacterial activity of purified PACs was 4 and 10 times higher than for water and water/ethanol extracts, respectively, but the extracts had higher anti-fungal activity. Purified PACs showed the ability to reduce IL-8 and IL-6 secretion from poly-I:C-stimulated peripheral blood mononuclear cells. For the extracts and PACs of SBT cultivar 'Maria Bruvele' in the concentration range 0.0313-4.0 mg/mL, no toxic effect was observed.

Phenolic Fraction from Peanut (Arachis hypogaea L.) By-product: Innovative Extraction Techniques and New Encapsulation Trends for Its Valorization

Peanut skin is a by-product rich in bioactive compounds with high nutritional and pharmaceutical values. The phenolic fraction, rich in proanthocyanidins/procyanidins, is a relevant class of bioactive compounds, which has been increasingly applied as functional ingredients for food and pharmaceutical applications and is mostly recovered from peanut skins through low-pressure extraction methods. Therefore, the use of green high-pressure extractions is an interesting alternative to value this peanut by-product. This review addresses the benefits of the phenolic fraction recovered from peanut skin, with a focus on proanthocyanin/procyanidin compounds, and discusses the improvement of their activity, bioavailability, and protection, by methods such as encapsulation. Different applications for the proanthocyanidins, in the food and pharmaceutical industries, are also explored. Additionally, high-pressure green extraction methods, combined with micro/nanoencapsulation, using wall material derived from peanut industrial processing, may represent a promising biorefinery strategy to improve the bioavailability of proanthocyanidins recovered from underutilized peanut skins.

Analysis of Proanthocyanidins in Plant Materials Using Hydrophilic Interaction HPLC-QTOF-MS

Proanthocyanidins (PACs) have been proven to possess a wide range of biological activities, but complex structures limit their study of structure–function relationships. Therefore, an efficient and general method using hydrophilic interaction high-performance liquid chromatography coupled with high-resolution quadrupole time-of-flight tandem mass spectrometry (HILIC-QTOF-MS) was established to analyze PACs from different plant materials. This method was successfully applied to characterize PACs from Chinese bayberry (Myrica rubra Sieb. et Zucc.) leaves (BLPs), sorghum testa (STPs) and grape seeds (GSPs). BLPs with the degree of polymerization (DP) from 1 to 8 were separated. BLPs are mainly B-type prodelphinidins and A-type BLPs were first found in this study. STPs and GSPs belonging to procyanidins showed DP from 3 to 11 and 2 to 12, respectively. A-type linkages were found for every DP of STPs and GSPs, which were first found. These results showed that HILIC-QTOF-MS can be successfully applied for analyzing PACs from different plant materials, which is necessary for the prediction of their potential health benefits.

Dietary proanthocyanidins promote localized antioxidant responses in porcine pulmonary and gastrointestinal tissues during Ascaris suum-induced type 2 inflammation

Proanthocyanidins (PAC) are dietary polyphenols with putative anti-inflammatory and immunomodulatory effects. However, whether dietary PAC can regulate type-2 immune function and inflammation at mucosal surfaces remains unclear. Here, we investigated if diets supplemented with purified PAC modulated pulmonary and intestinal mucosal immune responses during infection with the helminth parasite Ascaris suum in pigs. A. suum infection induced a type-2 biased immune response in lung and intestinal tissues, characterized by pulmonary granulocytosis, increased Th2/Th1 T cell ratios in tracheal-bronchial lymph nodes, intestinal eosinophilia, and modulation of genes involved in mucosal barrier function and immunity. Whilst PAC had only minor effects on pulmonary immune responses, RNA-sequencing of intestinal tissues revealed that dietary PAC significantly enhanced transcriptional responses related to immune function and antioxidant responses in the gut of both naïve and A. suum-infected animals. A. suum infection and dietary PAC induced distinct changes in gut microbiota composition, primarily in the jejunum and colon, respectively. Notably, PAC consumption substantially increased the abundance of Limosilactobacillus reuteri. In vitro experiments with porcine macrophages and intestinal epithelial cells supported a role for both PAC polymers and PAC-derived microbial metabolites in regulating oxidative stress responses in host tissues. Thus, dietary PAC may have distinct beneficial effects on intestinal health during infection with mucosal pathogens, while having a limited activity to modulate naturally-induced type-2 pulmonary inflammation. Our results shed further light on the mechanisms underlying the health-promoting properties of PAC-rich foods, and may aid in the design of novel dietary supplements to regulate mucosal inflammatory responses in the gastrointestinal tract.

Use of agro-industrial by-products containing tannins for the integrated control of gastrointestinal nematodes in ruminants

Previous studies have illustrated that different bioactive legume fodders containing condensed tannins might represent one of the options for integrated sustainable control of gastrointestinal nematodes (GIN) in ruminants, which may help address the worldwide development of resistance to synthetic anthelmintics. More recently, impetus has been given to assess the potential antiparasitic activity of less conventional resources, represented by different agro-industrial by-products (AIBPs). This review presents in vitro and in vivo results obtained with a range of tannin-containing AIBPs of various geographical and botanical origins, namely AIBP of nuts, temperate and tropical barks, carob, coffee and cocoa. They tend to confirm the "proof of concept" for their antiparasitic effects and also for other aspects of ruminant production in an agro-ecological context. Socio-economic aspects of the exploitation of such non-conventional resources are also discussed as potential models of the circular economy, by using waste. The different modes of use of these resources are presented in this review, as well as strengths, weaknesses, opportunities, and threats (SWOT) analyses to illustrate the advantages and limitations of on-farm use.

Garlic-derived organosulfur compounds regulate metabolic and immune pathways in macrophages and attenuate intestinal inflammation in mice

Scope: Garlic is a source of bioactive phytonutrients that may have anti‐inflammatory or immunomodulatory properties. The mechanism(s) underlying the bioactivity of these compounds and their ability to regulate responses to enteric infections remains unclear.

Methods and Results: This study investigates if a garlic‐derived preparation (PTSO‐PTS) containing two organosulfur metabolites, propyl‐propane thiosulfonate (PTSO), and propyl‐propane thiosulfinate (PTS), regulate inflammatory responses in murine macrophages and intestinal epithelial cells (IEC) in vitro, as well as in a model of enteric parasite‐induced inflammation. PTSO‐PTS decreases lipopolysaccharide‐induced secretion of TNFα, IL‐6, and IL‐27 in macrophages. RNA‐sequencing demonstrates that PTSO‐PTS strongly suppresses pathways related to immune and inflammatory signaling. PTSO‐PTS induces the expression of a number of genes involved in antioxidant responses in IEC during exposure to antigens from the parasite Trichuris muris. In vivo, PTSO‐PTS does not affect T. muris establishment or intestinal T‐cell responses but significantly alters cecal transcriptomic responses. Notably, a reduction in T. muris‐induced expression of Tnf, Saa2, and Nos2 is observed.

Conclusion: Garlic‐derived organosulfur compounds exert anti‐inflammatory effects in macrophages and IEC, and regulate gene expression during intestinal infection. These compounds and related organic molecules may thus hold potential as functional food components to improve gut health in humans and animals.