A-type Dimers Research Articles

New dimer integrable systems and defects in five dimensional gauge theory

We study the relation between the quantum integrable systems derived from the dimer graphs and five dimensional N = 1 supersymmetric gauge theories on S1 × ℝ4. We construct integrable systems based on new dimer graphs obtained from modification of hexagon dimer diagram. We study the gauge theories in correspondence to the newly proposed integrable systems. By examining three types of defects — a line defect, a canonical co-dimensional two defect and a monodromy defect — in five-dimensional gauge theory with N = 1 supersymmetry and Ωε1,ε2-background. We identify, in the ε2 → 0 limit, the canonical co-dimensional two defect satisfying the Baxter T-Q equation of the generalized A-type dimer integrable system, and the monodromy defect as its common eigenstate of the commuting Hamiltonians, with the eigenvalues being the expectation value of the BPS Wilson loop in the anti-symmetric representation of the bulk gauge group.

Studies on the orange red color development on the surface of the dried Ume (Prunus mume Sieb. et Zucc.) in a drying system equipped with full spectrum artificial sunlight

An orange-red fraction was obtained from fully sun-dried Ume (Prunus mume Sieb. et Zucc.) using a layer extraction method with acetone, methanol, and chloride as organic solvents. Liquid chromatography tandem-mass spectrometry (LC-MS/MS) analysis revealed a series of (-)-epicatechin (EC) dimers and trimers. The polymers were compared with published m/z negative mode and their fragments were characterized as procyanidin B2–2 (A-type dimer), procyanidin C1–2 (A-type trimer), and procyanidin C1–4 (dehydrotriepicatechin B1). High-performance liquid chromatography coupled with diode array detection (HPLC-DAD) analysis showed that the dehydrotriepicatechin B1 peak had an absorption maximum of 425 nm in the visible light range (400–600 nm). Similar results were obtained when salted Ume were subjected to simulated sunlight drying conditions using a low-temperature artificial drying system. Testing of blue light in an (-)-epicatechin (EC) model system showed the strongest catalytic effect. This study suggests that during sun-drying of salted Ume, (-)-epicatechin (EC) concentrates on the epidermis and undergoes photooxidative polymerization after sufficient sun exposure, further producing double bonds that cause the surface of sun-dried Ume to appear orange-red. This research has led to an innovative drying system that can replace sun-drying and avoid external factors such as insects, bacteria, meteorology, and food nutrition improvement that affect the quality of dried products.

UPLC-Q-TOF-MS and NMR identification of structurally different A-type procyanidins from peanut skin and their inhibitory effect on acrylamide.

Flavan-3-ol polyphenols have been shown to have great advantages in inhibiting acrylamide formation. However, flavan-3-ol polyphenols have structures that vary significantly, and existing research has been focused mainly on the effects of B-type procyanidins and structural units of procyanidins. This study aims to separate structurally different A-type procyanidins from peanut skin and compare their inhibitory effects on acrylamide in an asparagine-glucose simulation system. Five compounds were separated and identified from peanut skin, including epicatechin-(2β→ O→ 7, 4β→ 8)-ent-epicatechin, epicatechin-(2β→ O→ 7, 4β→ 8)-epicatechin, epicatechin-(2β→ O→ 7, 4β→ 8)-epicatechin-(4β→ 6)-catechin, epicatechin-(2β→ O→ 7, 4β→ 8)-epicatechin-(4β→ 8)-catechin, and epicatechin-(4β→ 6)-epicatechin-(4β→ 8, 2β→ O→ 7)-catechin. All the procyanidins could reduce the acrylamide content within a certain range of concentrations. The highest inhibition rates followed the order of compound 5 (A-type trimer) > compound 1 (A-type dimer) > compound 2 (A-type dimer) > compound 3 (A-type trimer) > compound 4 (A-type trimer). Comparison analysis showed that structurally different A-type procyanidins have various inhibitory effects on acrylamide production, which may be related to their spatial configuration and bond connection mode. Overall, our findings help us to gain a better understanding of the relationship between the structure of procyanidins and their inhibitory effects on acrylamide, particularly the inhibitory effect of A-type. There are potential practical implications if people use A-type procyanidins as acrylamide inhibitors in hot processed foods in the future. © 2022 Society of Chemical Industry.

In silico insights into the dimer structure and deiodinase activity of type III iodothyronine deiodinase from bioinformatics, molecular dynamics simulations, and QM/MM calculations

The homodimeric family of iodothyronine deiodinases (Dios) regioselectively remove iodine from thyroid hormones. Currently, structural data has only been reported for the monomer of the mus type III thioredoxin (Trx) fold catalytic domain (Dio3Trx), but the mode of dimerization has not yet been determined. Various groups have proposed dimer structures that are similar to the A-type and B-type dimerization modes of peroxiredoxins. Computational methods are used to compare the sequence of Dio3Trx to related proteins known to form A-type and B-type dimers. Sequence analysis and in silico protein-protein docking methods suggest that Dio3Trx is more consistent with proteins that adopt B-type dimerization. Molecular dynamics (MD) simulations of the refined Dio3Trx dimer constructed using the SymmDock and GalaxyRefineComplex databases indicate stable dimer formation along the β4α3 interface consistent with other Trx fold B-type dimers. Free energy calculations show that the dimer is stabilized by interdimer interactions between the β-sheets and α-helices. A comparison of MD simulations of the apo and thyroxine-bound dimers suggests that the active site binding pocket is not affected by dimerization. Determination of the transition state for deiodination of thyroxine from the monomer structure using QM/MM methods provides an activation barrier consistent with previous small model DFT studies. Communicated by Ramaswamy H. Sarma

In Vitro Faecal Fermentation of Monomeric and Oligomeric Flavan-3-ols: Catabolic Pathways and Stoichiometry.

The study evaluates the influence of flavan-3-ol structure on the production of phenolic catabolites, principally phenyl-γ-valerolactones (PVLs), and phenylvaleric acids (PVAs). A set of 12 monomeric flavan-3-ols and proanthocyanidins (degree of polymerization (DP) of 2-5), are fermented in vitro for 24 h using human faecal microbiota, and catabolism is analyzed by UHPLC-ESI-MS/MS. Up to 32 catabolites strictly related to microbial catabolism of parent compounds are detected. (+)-Catechin and (-)-epicatechin have the highest molar mass recoveries, expressed as a percentage with respect to the incubated concentration (75µmol L-1 ) of the parent compound, for total PVLs and PVAs, both at 5 h (about 20%) and 24 h (about 40%) of faecal incubation. Only A-type dimer and B-type procyanidins underwent the ring fission step, and no differences are found in total PVL and PVA production (≃1.5% and 6.0% at 5 and 24 h faecal incubation, respectively) despite the different DPs. The flavan-3-ol structure strongly affects the colonic catabolism of the native compounds, influencing the profile of PVLs and PVAs produced in vitro. This study opens new perspectives to further elucidate the colonic fate of oligomeric flavan-3-ols and their availability in producing bioactive catabolites.

PHYTOTOXIC ACTION OF Machaerium amplum BENTH. LEAVES EXTRACT

The indiscriminate use of herbicides can guide to some environmental damages. Thus, the search for alternative bioherbicides from natural sources with biodegradable properties and less toxicity to the microbiota is essential. The focus of this work is the chemistry and phytotoxic study of the hydroethanolic extract of Machaerium amplum Benth. leaves. The chemical study by FIA-ESIIT-MSn experiments allowed the detection of apigenin and luteolin C-glycoside derivatives, quinic acid, the A-type proanthocyanidin dimer and trimer, and a saponin Soyasapogenol B type. Phytotoxicity assays were performed with the extract and a group of fractions against tomato and onion seeds under the parameters of germination, hypocotyl growth, and root length. The extract showed a 70% of inhibition effect at 0.8 mg.mL-1 on tomato root length. For the onion seeds, the percentual of inhibition was 65% at 0.4 mg.mL-1 . All groups of fractions tested showed significant inhibition on tomato seedling root length at 0.8 mg.mL-1 . The flavonoids fraction showed interesting activity at 0.4 mg.mL-1 . The same fraction showed a percentage of inhibition above 50% at 0.2 mg.mL-1 on onion seedling root length. This activity may be associated with the C-flavones presence in this fraction. According to the ecotoxicity test with Artemia salina Leach, the extract presents no toxicity at the concentrations tested, and no antimicrobial activity against Fusarium graminearum, F. oxysporum and Aspergillus flavus, thus reinforcing the potential of the extract.

Metabolomic profiles of A-type procyanidin dimer and trimer with gut microbiota in vitro

Although intestinal microbiota plays an important role in the metabolism of procyanidins, the microbial metabolic pathway of A-type procyanidins remains elusive. In this study, A-type dimer procyanidin A1 [EC-(2β-O-7,4β-8)-C] and trimer PPD [EC-(4β-6)-EC-(2β-O-7,4β-8)-C] were incubated with rat faecal microbiota in vitro, and their metabolomic profiles were analyzed by UPLC-QTOF/MS. Multivariate statistical analysis identified 24 and 30 discriminant metabolites for A1 and PPD, respectively. The C-ring opened catabolites of procyanidin A1 and PPD and the typical phenolic acid metabolites were identified, including phenylacetic acid, (4′-hydroxyphenyl)acetic acid, 3-phenylpropanoic acid, 3-(4′-hydroxyphenyl)propanoic acid, 3-(3′,4′-dihydroxyphenyl)propanoic acid, and 5-(3′,4′-dihydroxyphenyl)-γ-valerolactone. Notably, procyanidin A1 and (epi)catechin were identified from the metabolites of PPD; however, no (epi)catechin was found in the metabolites of procyanidin A1, indicating that the faecal microbiota can destroy B-type linkage (C4-C6 interflavan bond) but not A-type linkage (C4-C8 and additional C2-O-C7 interflavan bond) in the metabolism of A-type procyanidins.

Metabolites of Procyanidins From Litchi Chinensis Pericarp With Xanthine Oxidase Inhibitory Effect and Antioxidant Activity.

Procyanidins from litchi pericarp (LPPC) has been evidenced to possess strong antioxidant activities in vivo that is possibly correlated with their intestinal metabolites. However, the xanthine oxidase inhibitory effect of LPPC and its metabolites was less concerned. In this study, three oligomeric procyanidins and eight metabolic phenolic acids were identified in the urine of rats administrated with LPPC by high performance liquid chromatography and liquid chromatography-mass spectrometry analysis. Data indicated that all the metabolites excreted were significantly increased by the treatment of 300 mg/kg body weight of LPPC (P < 0.05), revealing considerable 1, 1-Diphenyl-2-Picrylhydrazyl (DPPH) and hydroxyl radicals activities of scavenging. Moreover, phenolic metabolites involving epicatechin, A-type dimer, A-type trimer, caffeic acid, and shikimic acid exhibited greater xanthine oxidase inhibition effects compared with other metabolites, with an inhibitory rate higher than 50% at the concentration 200 μg/ml. The IC50 value of these five phenols were 58.43 ± 1.86, 68.37 ± 3.50, 74.87 ± 1.30, 95.67 ± 3.82, and 96.17 ± 1.64 μg/ml, respectively. As a whole, this work suggests that the xanthine oxidase inhibition and antioxidant activity of LPPC-derived metabolites as one of the mechanisms involved in the beneficial effects of LPPC against hyperuricemia or gout.

Proanthocyanidin in the fruit of Japanese apricot (Prunus mume Sieb. et Zucc.) and their structural estimation by HPLC-ESI-MS/MS

Proanthocyanidins (PAs) contribute to the quality factors and health benefits of several Rosaceae fruits. Ume, also known as Japanese apricot (Prunus mume Sieb. Et. Zucc), is one of the most popular fruit trees grown in Japan, and its processed products are employed as a folk remedy in eastern Asian countries. However, the information available regarding the PAs present in the fruit remains limited. In this study, we analyzed the PAs and phenolic acid derivatives present in the fruit of ‘Nnanko,’ the most common cultivar, and found that the flesh tissue of the mature fruit contained levels of PAs similar to those of the hydroxycinnamic acids. The concentration of PAs in the endocarp tissue of the mature fruit was approximately 14 times higher than that of the flesh tissue. We also estimated the chemical structures of the PAs from the flesh and the endocarp by HPLC-ESI-MS/MS. Although 13 kinds of PAs, including 2 monomers, 4 B-type dimers, 3 A-type dimers, 2 B-type trimers, 1 A-type trimer, and 1 B-type tetramer were detected in the flesh, only 2 monomers, 1 B-type dimer, and 2 A-type dimers were detected in the endocarp. All PAs detected in the endocarp were also present in the flesh.

Protective effect of procyanidin A-type dimers against H2O2-induced oxidative stress in prostate DU145 cells through the MAPKs signaling pathway

It has been reported that B-type procyanidins can alleviate oxidative damage of prostatic cells, but there has been limited information on the similar role of A-type procyanidins. This study investigated the protective effect of procyanidin A-type dimers from peanut skin against H2O2-induced oxidative stress damage in prostate cancer DU145 cells. According to the UPLC-Q-TOF-MS/MS analysis and comparison with standards, the fourth fraction of peanut skin procyanidin (PSP-4) was identified as procyanidin A-type dimers, namely, procyanidin A1 and A2. Results revealed that PSP-4 treatment prior H2O2 exposure increased cell activity and attenuated the cell cycle arrest and apoptosis rate. The H2O2-induced increase in intracellular reactive oxygen species (ROS) was remarkably inhibited by PSP-4. PSP-4 treatment enhanced the activity of catalase (CAT) and total super oxide dismutase (T-SOD) and restored glutathione (GSH) content, compared with the H2O2 treatment. Furthermore, the results indicated that PSP-4 protected DU145 cells by attenuating phosphorylation of the mitogen-activated protein kinases (MAPKs), by increasing the Bcl-2/Bax ratio, and by reducing the activation of caspase-3 and caspase-9 by cascade reactions. This study reveals that procyanidin A-type dimers from peanut skin have the potential function in preventing oxidative stress damage of prostatic cells.

Rare A-Type, Spiro-Type, and Highly Oligomeric Proanthocyanidins from Pinus massoniana.

An investigation of the dental bioactive proanthocyanidin (PAC) oligomer fractions led to three structurally distinct new PACs (1-3) from pine bark. Pinutwindoublin (1) is the first reported trimer with double A-type interflavanyl linkages (2α→O→5,4α→6 and 2α→O→7,4α→8). Pinuspirotetrin (2) represents the first reported PAC tetramer with a heterodimeric framework consisting of one spiro-type and one A-type dimer. Pinumassohexin (3) was elucidated as a mixed A + B-type hexamer that consists of a peanut-derived tetramer, peanut procyanidin E, and an A-type dimer (5). Compound 3 increased the modulus of elasticity of dentin by an impressive 4.3 times at a concentration of 0.65%.

Tri- and Tetrameric Proanthocyanidins with Dentin Bioactivities from Pinus massoniana.

Guided by dentin biomechanical bioactivity, this phytochemical study led to the elucidation of an extended set of structurally demanding proanthocyanidins (PACs). Unambiguous structure determination involved detailed spectroscopic and chemical characterization of four A-type dimers (2 and 4-6), seven trimers (10-16), and six tetramers (17-22). New outcomes confirm the feasibility of determining the absolute configuration of the catechol monomers in oligomeric PACs by one-dimensional (1D) and two-dimensional (2D) NMR. Electronic circular dichroism as well as phloroglucinolysis followed by mass spectrometry and chiral phase high-performance liquid chromatography (HPLC) analysis generated the necessary chiral reference data. In the context of previously reported dentin-bioactive PACs, accurately and precisely assigned 13C NMR resonances enabled absolute stereochemical assignments of PAC monomers via (i) inclusion of the 13C NMR γ-gauche effect and (ii) determination of differential 13C chemical shift values (ΔδC) in comparison with those of the terminal monomer (unit II) in the dimers 2 and 4-6. Among the 13 fully elucidated PACs, eight were identified as new, and one structure (11) was revised based on new knowledge gained regarding the subtle, stereospecific spectroscopic properties of PACs.

Chemical composition of thermally processed coconut water evaluated by GC–MS, UPLC-HRMS, and NMR

Thermally-processed coconut water often develop a commercially-undesirable pink color, thus, NMR, UPLC-HRMS, GC–MS analyses combined with chemometrics approach were applied to evaluate chemical variations in comparison to tender water (control) that could explain such color change. Chemometrics on negative ionization mode dataset showed trimeric and A-type dimeric procyanidins, and caffeoylshikimic acid as main identified secondary metabolites induced by processing, while, control water presented mainly cytokinin trans-zeatin riboside, procyanidin dimer, caffeoylshikimic acid and trihydroxy-octadecenoic acid. Processing increased long-chain saturated palmitic and stearic fatty acids contents, meanwhile NMR analysis showed a decline in primary metabolites content as sugars fructose and glucose, and short-chain organic acids. Among the results observed for thermally processed coconut water, the increase in oligomeric procyanidins as A-type dimer and trimer may be associated with pink color development as these are precursors of anthocyanin pigment and/or by enhancing color stability of anthocyanin solutions.

High performance thin-layer chromatography–mass spectrometry methods on diol stationary phase for the analyses of flavan-3-ols and proanthocyanidins in invasive Japanese knotweed

We developed the first four HPTLC methods for the separation of proanthocyanidins according to degree of polymerization on HPTLC diol F254S plates. Acetonitrile, ethyl acetate, ethyl acetate–formic acid (9:0.1, v/v) and toluene–acetone–formic acid (3:6:1, v/v) were used as developing solvents and 4-dimethylaminocinnamaldehyde (DMACA) as the detection reagent. Each of these methods enables separation of standards of procyanidin dimers from procyanidin trimer (procyanidin C1) and separation of B-type dimers (procyanidins B1, B2, B3) from A-type dimers (procyanidins A1, A2). Based on these HPTLC methods we developed four new HPTLC-MS/MS methods for analyses of proanthocyanidins on HPTLC diol F254S plates and we identified B-type proanthocyanidins from monomers up to decamers in crude extracts of invasive Japanese knotweed (Fallopia japonica Houtt., Polygonum cuspidatum Sieb. & Zucc.) rhizomes. Monomers, monomer gallates, dimers, dimer gallates, dimer digallates, trimers, trimer gallates, tetramers, tetramer gallates, pentamers, pentamer gallates, hexamers, hexamer gallates, heptamers, octamers, nonamers and decamers were tentatively identified in Japanese knotweed rhizomes using developing solvents acetonitrile and toluene–acetone–formic acid (3:6:1, v/v). Ethyl acetate enabled separation from monomers up to hexamer gallates and ethyl acetate–formic acid (9:0.1, v/v) from monomers up to hexamers. During the five hours of stability testing of (–)-epicatechin and procyanidin B2 standards on HPTLC diol plates developed with all solvents we observed enhanced absorption at 280 nm. This was a totally unexpected phenomenon. This new discovery confirmed what we reported in our previous study on HPTLC silica gel. Enhanced absorption is influenced by the developing solvent (more than 30%), the stationary phase (up to 24%) and the light (up to 15%).

Polyphenolic Characterization and Antioxidant Activity of Malus domestica and Prunus domestica Cultivars from Costa Rica.

The phenolic composition of skin and flesh from Malus domestica apples (Anna cultivar) and Prunus domestica plums (satsuma cultivar) commercial cultivars in Costa Rica, was studied using Ultra Performance Liquid Chromatography coupled with High Resolution Mass Spectrometry (UPLC-DAD-ESI-MS) on enriched-phenolic extracts, with particular emphasis in proanthocyanidin and flavonoids characterization. A total of 52 compounds were identified, including 21 proanthocyanidins ([(+)-catechin and (−)-epicatechin]) flavan-3-ols monomers, five procyanidin B-type dimers and two procyanidin A-type dimers, five procyanidin B-type trimers and two procyanidin A-type trimers, as well as one procyanidin B-type tetramer, two procyanidin B-type pentamers, and two flavan-3-ol gallates); 15 flavonoids (kaempferol, quercetin and naringenin derivatives); nine phenolic acids (protochatechuic, caffeoylquinic, and hydroxycinnamic acid derivatives); five hydroxychalcones (phloretin and 3-hydroxyphloretin derivatives); and two isoprenoid glycosides (vomifoliol derivatives). These findings constitute the first report of such a high number and diversity of compounds in skins of one single plum cultivar and of the presence of proanthocyanidin pentamers in apple skins. Also, it is the first time that such a large number of glycosylated flavonoids and proanthocyanidins are reported in skins and flesh of a single plum cultivar. In addition, total phenolic content (TPC) was measured with high values observed for all samples, especially for fruits skins with a TPC of 619.6 and 640.3 mg gallic acid equivalents/g extract respectively for apple and plum. Antioxidant potential using 2,2-diphenyl-1-picrylhidrazyl (DPPH) and oxygen radical absorbance capacity (ORAC) methods were evaluated, with results showing also high values for all samples, especially again for fruit skins with IC50 of 4.54 and 5.19 µg/mL (DPPH) and 16.8 and 14.6 mmol TE/g (ORAC) respectively for apple and plum, indicating the potential value of these extracts. Significant negative correlation was found for both apple and plum samples between TPC and DPPH antioxidant values, especially for plum fruits (R = −0.981, p < 0.05) as well as significant positive correlation between TPC and ORAC, also especially for plum fruits (R = 0.993, p < 0.05) and between both, DPPH and ORAC antioxidant methods (R = 0.994, p < 0.05).

P.3.c.005 - Pre-clinical evaluation of two novel benzamides, LB-102 and 103, for the treatment of schizophrenia

The berries of Vaccinium macrocarpon, cranberry, are widely used for the prevention of urinary tract infections. This species contains A-type proanthocyanidins (PACs), which intervene in the initial phase of the development of urinary tract infections by preventing the adherence of Escherichia coli by their P-type fimbriae to uroepithelial cells. Unfortunately, the existing clinical studies used different cranberry preparations, which were poorly standardized. Because of this, the results were hard to compare, which led sometimes to conflicting results. Currently, PACs are quantified using the rather non-specific spectrophotometric 4-dimethylaminocinnamaldehyde (DMAC) method. In addition, a normal phase HPTLC-densitometric method, a HPLC-UV method and three LC–MS/MS methods for quantification of procyanidin A2 were recently published. All these methods contain some shortcomings and errors. Hence, the development and validation of a fast and sensitive standard addition LC–MS/MS method for the simultaneous quantification of A-type dimers and trimers in a cranberry dry extract was carried out. A linear calibration model could be adopted for dimers and, after logaritmic transformation, for trimers. The maximal interday and interconcentration precision was found to be 4.86% and 4.28% for procyanidin A2, and 5.61% and 7.65% for trimeric PACs, which are all acceptable values for an analytical method using LC–MS/MS. In addition, twelve different cranberry extracts were analyzed by means of the newly validated method and other widely used methods. There appeared to be an enormous variation in dimeric and trimeric PAC content. Comparison of these results with LC–MS/MS analysis without standard addition showed the presence of matrix effects for some of the extracts and proved the necessity of standard addition.A comparison of the well-known and widely used DMAC method, the butanol-HCl assay and this newly developed LC–MS/MS method clearly indicated the need for a reliable method able to quantify A-type PACs, which are considered to be the pharmacologically active constituents of cranberry, since neither the DMAC or butanol-HCl assays are capable of distinguishing between A and B-type PACs and therefore cannot detect adulterations with, for example, extracts with a high B-type PAC content. Hence, the combination of the DMAC method or butanol-HCl assay with this more specific LC–MS/MS assay could overcome these shortcomings.

Advantages of a validated UPLC–MS/MS standard addition method for the quantification of A-type dimeric and trimeric proanthocyanidins in cranberry extracts in comparison with well-known quantification methods

The berries of Vaccinium macrocarpon, cranberry, are widely used for the prevention of urinary tract infections. This species contains A-type proanthocyanidins (PACs), which intervene in the initial phase of the development of urinary tract infections by preventing the adherence of Escherichia coli by their P-type fimbriae to uroepithelial cells. Unfortunately, the existing clinical studies used different cranberry preparations, which were poorly standardized. Because of this, the results were hard to compare, which led sometimes to conflicting results. Currently, PACs are quantified using the rather non-specific spectrophotometric 4-dimethylaminocinnamaldehyde (DMAC) method. In addition, a normal phase HPTLC-densitometric method, a HPLC-UV method and three LC–MS/MS methods for quantification of procyanidin A2 were recently published. All these methods contain some shortcomings and errors. Hence, the development and validation of a fast and sensitive standard addition LC–MS/MS method for the simultaneous quantification of A-type dimers and trimers in a cranberry dry extract was carried out. A linear calibration model could be adopted for dimers and, after logaritmic transformation, for trimers. The maximal interday and interconcentration precision was found to be 4.86% and 4.28% for procyanidin A2, and 5.61% and 7.65% for trimeric PACs, which are all acceptable values for an analytical method using LC–MS/MS. In addition, twelve different cranberry extracts were analyzed by means of the newly validated method and other widely used methods. There appeared to be an enormous variation in dimeric and trimeric PAC content. Comparison of these results with LC–MS/MS analysis without standard addition showed the presence of matrix effects for some of the extracts and proved the necessity of standard addition.A comparison of the well-known and widely used DMAC method, the butanol-HCl assay and this newly developed LC–MS/MS method clearly indicated the need for a reliable method able to quantify A-type PACs, which are considered to be the pharmacologically active constituents of cranberry, since neither the DMAC or butanol-HCl assays are capable of distinguishing between A and B-type PACs and therefore cannot detect adulterations with, for example, extracts with a high B-type PAC content. Hence, the combination of the DMAC method or butanol-HCl assay with this more specific LC–MS/MS assay could overcome these shortcomings.

Comprehensive phenolic composition analysis and evaluation of Yak-Kong soybean (Glycine max) for the prevention of atherosclerosis

Yak-Kong (YK) (Glycine max), a small black soybean cultivar with a green embryo, was evaluated for functional constituents with a focus on atherosclerosis prevention. In comparison to common yellow and black soybean cultivars, YK contains significantly higher concentrations of antioxidants, particularly in its seed coat. A comprehensive phenolic composition analysis revealed that proanthocyanidins were the major phenolic group in YK. In contrast to other proanthocyanidin-rich foods, YK was rich in bioavailable proanthocyanidins (with a degree of polymerization ≤3) specifically with A-type dimers. Significant concentrations of phloridzin and coumestrol were also exclusively found in YK seed coat and the embryo, respectively. Extracts of both the proanthocyanidin-rich seed coat and isoflavonoid-rich embryo of YK attenuated adhesion of THP-1 to LPS-stimulated human umbilical vascular endothelial cells, suggesting that they are important sources of coronary heart disease-preventive phenolics. YK has promising potential for further development as a functional food source targeted at atherosclerosis prevention.

Trimeric and Tetrameric A-Type Procyanidins from Peanut Skins.

Peanut skins are a rich source of oligomeric and polymeric procyanidins. The oligomeric fractions are dominated by dimers, trimers, and tetramers. A multistep chromatographic fractionation led to the isolation of four new A-type procyanidins of tri- and tetrameric structures. The structures of the new trimers were defined by NMR, electronic circular dichroism, and MS data as epicatechin-(4β→8,2β→O→7)-epicatechin-(4β→8,2β→O→7)-catechin, peanut procyanidin B (3), and epicatechin-(4β→8,2β→O→7)-epicatechin-(4β→6)-catechin, peanut procyanidin C (4). The new tetramers were defined as epicatechin-(4β→8,2β→O→7)-epicatechin-(4β→6)-epicatechin-(4β→8,2β→O→7)-catechin, peanut procyanidin E (1), and epicatechin-(4β→8,2β→O→7)-epicatechin-(4β→6)-epicatechin-(4β→8,2β→O→7)-epicatechin, peanut procyanidin F (2). In addition, both A-type dimers A1, epicatechin-(4β→8,2β→O→7)-catechin, and A2, epicatechin-(4β→8,2β→O→7)-epicatechin, as well as two known peanut trimers, ent-epicatechin-(4β→6)-epicatechin-(4β→8,2β→O→7)-catechin, peanut procyanidin A (5), and epicatechin-(4β→8)-epicatechin-(4β→8,2β→O→7)-catechin, peanut procyanidin D (6), were also isolated. Dimer A1, the four trimers, and two tetramers were evaluated for anti-inflammatory activity in an in vitro assay, in which LPS-stimulated macrophages were responding with secretion of TNF-α, a pro-inflammatory cytokine. Tetramer F (2) was the most potent, suppressing TNF-α secretion to 82% at 8.7 μM (10 μg/mL), while tetramer E (1) at the same concentrations caused a 4% suppression. The results of the TNF-α secretion inhibition indicate that small structural differences, as in peanut procyanidin tetramers E and F, can be strongly differentiated in biological systems.

Absolute Configuration of Native Oligomeric Proanthocyanidins with Dentin Biomodification Potency.

The structurally complex oligomeric proanthocyanidins (OPACs) are promising biomimetic agents, capable of strengthening the macromolecular backbone of teeth via intermolecular and intermicrofibrillar cross-linking. This study establishes analytical methods capable of determining the absolute configuration of the catechin-type monomeric units of underivatized OPACs. This preserves the capacity of their biological evaluation, aimed at understanding the inevitably stereospecific interactions between the OPACs and dentin collagen. Guided by dental bioassays (modulus of elasticity, long-term stability), two new trimeric and tetrameric A-type OPACs were discovered as dentin biomodifiers from pine (Pinus massoniana) bark: epicatechin-(2β→O→7,4β→8)-epicatechin-(2β→O→7,4β→8)-catechin (5) and epicatechin-(2β→O→7,4β→8)-epicatechin-(2β→O→7,4β→6)-epicatechin-(2β→O→7,4β→8)-catechin (6), respectively. Combining 1D/2D NMR, HRESIMS, ECD, 1H iterative full spin analysis (HiFSA), and gauge-invariant atomic orbital (GIAO) δ calculations, we demonstrate how 13C NMR chemical shifts (diastereomeric building blocks (A-type dimers)) empower the determination of the absolute configuration of monomeric units in the higher oligomers 5 and 6. Collectively, NMR with ECD reference data elevates the level of structural information achievable for these structurally demanding molecules when degradation analysis is to be avoided. Considering their numerous and deceptively subtle, but 3D impactful, structural variations, this advances the probing of OPAC chemical spaces for species that bind selectively to collagenous and potentially other biologically important biomacromolecules.