•Persimmon tannins increased pectin's gel strength.•All tannin-pectin complex gels showed a rapid formation with G′ > G′′.•Pectin/tannin complex gels had aggregated network.The effects of persimmon tannins with different average degrees of polymerization (DP26 and DP5) on the rheological and microstructural properties of high- and low-methoxyl (HM/LM) pectin gel were investigated. The gel properties were analyzed by large-deformation and dynamic rheological measurements, and the complex gels microstructure was also characterized using scanning electron microscopy (SEM). Persimmon tannins (DP26/5) could significantly enhance the strength of HM and LM pectin gels (p < 0.05) that was about twice that of pectin alone, especially with high concentrations of tannins (2 g/L). Besides, the rheological results indicated that the addition of persimmon tannins increased the gelling ability of HM/LM pectins, and all tannin-pectin complex gels displayed a typical weak gel-like (G′ > G″) structure. Furthermore, SEM analyses revealed the heterogeneous and aggregated network of the gels containing persimmon tannins, because of the intermolecular cross-linking between the carboxyl groups of pectin molecule and the phenolic hydroxyl groups of tannins through hydrogen bonds and hydrophobic interaction. Overall, DP5 tannins enhanced gel properties of HM/LM pectins more than DP26 tannins, probably due to the larger size, steric hindrance and self-association of DP26 tannins.

Persimmon tannin (PT) has been shown to inhibit snake venom activities and toxicities both in vitro and in vivo. To clarify the detoxifying mechanism of PT on snake venom, the interaction of characteristic structural elements of PT (EGCG, ECG, EGCG dimer and ECG dimer) and Chinese cobra phospholipase A2 (PLA2) was studied. The results revealed that except non-covalent bonds like hydrogen bonds, hydrophobic bonds and iron bonds were formed between PT and PLA2, covalent interaction was also occurred. PT could bind with the key active residues of PLA2, such as lysine, histidine, tryptophan and tyrosine, restraining their activity and disturbing the structure of PLA2, thus showing detoxifying effects on snake venom.Download high-res image (75KB)Download full-size image

The influence of the planting season on the nutritional as well as the aromatic composition of Hezuo 903 tomato was investigated by combining use of nutrition analysis, sensory evaluation, electronic nose and electronic tongue analysis, gas chromatography–mass spectrometry (GC–MS) and GC–MS–olfactometry (GC–MS–O) method. The results suggested that in-season tomato contained higher levels of reducing sugar, vitamin C and lycopene than off-season tomato. In-season tomato showed a better overall flavor and acceptability than off-season tomato. Significant difference was observed in both composition and concentration of the typical volatile and aroma-active compounds in two samples. E-2-Hexenal and methyl salicylate were only found in off-season tomato, and phenylacetaldehyde detected merely in in-season tomato. In addition, significantly higher levels of 6-methyl-5-hepten-2-one (P < 0.01) and 2-isobutylthiazole (P < 0.01) were detected in off-season tomato than in-season tomato, which showed a negative effect on the overall flavor of tomato. Our result indicated that the planting season affected the composition and concentration of both non-volatile and volatile compounds of tomato fruit.

•The effects of A-type EGCG dimer on preformed amyloid fibrils were studied by biophysical methods.•A-type EGCG dimer decreased the surface hydrophobicity of amyloid fibrils.•The amyloid fibrils were disaggregated into amorphous aggregates and soluble species by A-type EGCG dimer.•A-type EGCG dimer might be used as an important lead structure for the design of anti-amyloid drugs.In the present study, the disruptive effects of epigallocatechin-3-gallate (EGCG) and A-type dimeric epigallocatechin-3-gallate (A-type EGCG dimer) on the preformed bovine insulin amyloid fibrils were studied by several biophysical methods including thioflavin-T (ThT) fluorescence assay, 1-anilinonaphthalene-8-sulfonic (ANS) fluorescence assay, Congo red (CR) binding assay, dynamic light scattering (DLS), transmission electron microscopy (TEM), Gel electrophoresis (SDS-PAGE) and Bradford assay. Our results demonstrated that A-type EGCG dimer showed significantly more potential disaggregative effects on the bovine insulin amyloid fibrils than EGCG. A-type EGCG dimer could not only dramatically promote the disaggregation of the preformed bovine insulin amyloid fibrils, but also restructure the amyloid fibrils into amorphous aggregates. While, EGCG could only shorten and thin the fibrils, but induce no small amorphous aggregates. Our present results provided additional evidence for the more potent disaggregation effects of dimeric polyphenols than monomeric polyphenols and suggested that A-type EGCG dimer seems to have potential application as an excellent anti-amyloidogenic agent.Download high-res image (264KB)Download full-size image

•The content of GCG is almost the same as or higher than EGCG in canned and bottled tea drinks.•GCG significantly reduced the intracellular lipid droplets and expressions of major adipogenic transcription factors.•GCG treatment decreased the intracellular ROS level, attenuated MAPK pathway activation.•GCG decreased the activation of NF-κB, down-regulated the production of IL-6 and MCP-1 induced by LPS.Gallocatechin gallate (GCG), as the epimer of Epigallocatechin gallate (EGCG), the content is low in traditional tea made from Camellia sinensis and C. assamica. However, previous studies found that the content of GCG was almost the same as EGCG in canned and bottled tea drinks. Accumulating evidences indicated that GCG possessed multiple biological activities, but the anti-obesity study of GCG is poorly reported. In this study, the anti-adipogenic activities of GCG were investigated. The results showed that as EGCG, GCG significantly reduced the intracellular lipid droplets and expressions of major adipogenic transcription factors, such as PPAR γ, SREBP-1c and C/EBP α. Further study revealed that the expressions of FAS, ACC, FAT and SCD-1 were decreased in 3T3-L1 cells treated with GCG. GCG treatment also dose-dependently decreased the intracellular ROS level, attenuated MAPK pathway activation in 3T3-L1 differentiations. Additionally, GCG decreased the activation of NF-κB, and down-regulated the production of IL-6 and MCP-1 induced by LPS.

•PT characteristic elements could neutralize the lethality, myotoxicity, and hemolysis of Chinese cobra PLA2.•The detoxifying effects of PT structural elements correlated well with their structural disturbing effects on PLA2.•EGCG dimer and ECG dimer may be structural requirements for the detoxifying effects of persimmon tannin.•The great spatial structural disturbance of PLA2 induced by PT may be responsible for their detoxifying activities in vivo.The effects of persimmon tannin (PT) characteristic structural elements on Naja atra phospholipase A2 (PLA2)-induced lethality, myotoxicity, and hemolysis in mice models were determined. In addition, methods including surface plasmon resonance, dynamic light scattering, and Fourier transform infrared spectroscopy were explored to uncover the possible detoxifying mechanisms of PT on snake venom PLA2. Our results revealed that PT characteristic elements (EGCG, ECG, A-type EGCG dimer, and A-type ECG dimer) could neutralize the lethality, myotoxicity, and hemolysis of PLA2. Moreover, the detoxifying effects of the four structural elements correlated with their structural disturbing effects well. Our results proved that A-type EGCG dimer and A-type ECG dimer may be structural requirements for the detoxifying effects of PT. We propose that the high affinity of A-type EGCG dimer and A-type ECG dimer for PLA2 and the considerable spatial structural disturbance of PLA2 induced by the dimers may be responsible for their antilethality, antimyotoxicity, and antihemolysis on Chinese cobra PLA2 in vivo.Download high-res image (162KB)Download full-size image

•Persimmon tannin promoted cholesterol efflux by ERK1/2-PPARγ pathway in vitro.•Persimmon tannin facilitated RCT in high-cholesterol diet fed C57BL/6J mice.•Inhibition of persimmon tannin on ERK1/2 contributed to macrophage RCT in vivo.The purpose of this study was to investigate whether persimmon tannin is associated with cholesterol efflux and macrophage-reverse cholesterol transport (RCT). In J774A.1 macrophage cells, persimmon tannin could inhibit cellular cholesterol accumulation and promote 22-NBD-cholesterol efflux through inhibiting the phosphorylation of ERK1/2 and up-regulating the protein levels of PPARγ. Macrophage RCT in vivo was evaluated by injecting 22-NBD-cholesterol-loaded J774A.1 macrophages intraperitoneally into C57BL/6J mice. Administration of persimmon tannin significantly (P < 0.05) decreased the cholesterol concentration in both serum and liver, and increased faecal cholesterol excretion compared with the high-cholesterol group. In transcriptional levels, persimmon tannin enhanced the expression of cholesterol transport-related genes (ABCA1, LCAT, ABCG5/G8, NPC1L1 and CYP7A1) and their upstream nuclear receptors (PPARγ, PPARα and LXRα). Moreover, the regulation of persimmon tannin on RCT-related genes might be mediated by its inhibition on ERK1/2 in mice. Therefore, persimmon tannin promoted macrophage reverse cholesterol transport through the regulation on ERK1/2-PPARγ signaling pathway both in vitro and in vivo.

The present study aimed to explore the underlying mechanisms of epicatechin-3-gallate-(4β→8, 2β→O→7)-epicatechin-3-gallate (A-type ECG dimer) and epigallocatechin-3-gallate-(4β→8, 2β→O→7)-epigallocatechin-3-gallate (A-type EGCG dimer) involved in their strong inhibitory effects on 3T3-L1 preadipocytes differentiation. In the synthetic “lipid raft-like” liposome, A-type ECG and EGCG dimers incorporated into the liposome with high affinity and decreased the fluidity of the liposome. In 3T3-L1 preadipocytes, A-type ECG and EGCG dimers possibly bonded to lipid rafts cholesterol and disrupted the integrity of lipid rafts, thus exerting their notable inhibitory effects on 3T3-L1 preadipocytes differentiation by suppressing mitotic clonal expansion process and mRNA levels of PPARγ, C/EBPα and SREBP1C. A highly positive correlation between the cholesterol binding capacity of the two dimers and their inhibitory effect on 3T3-L1 preadipocytes differentiation (R2=0.9328) was observed. Molecular dynamics simulation further verified that A-type ECG and EGCG dimers could bond to cholesterol via hydrogen bonding. The results of this study suggested that the disruption of A-type ECG and EGCG dimers on membrane lipid rafts by targeting cholesterol in the lipid rafts was involved in the underlying mechanisms of their strong inhibitory effects on 3T3-L1 preadipocytes differentiation. This broadens the understanding of the molecular mechanisms of polyphenols on modulating and controlling of metabolic dysregulation, particularly adipocyte differentiation, which is a significant risk factor associated with the development of cardiovascular disease.

•Persimmon tannin shows significant hypocholesterolaemic properties in in vitro studies.•The uptake of 22-NBD-cholesterol can be inhibited by persimmon tannin intervention.•Persimmon tannin down-regulated the expression of NPC1L1 genes.•Persimmon tannin exhibited potential in promoting cellular cholesterol efflux.•The regulation of persimmon tannin on cholesterol homeostasis was LXRα independent.Persimmon tannin (proanthocyanidins) has been proven to exert significant hypocholesterolaemic effects in a variety of models. However, the regulatory mechanisms of persimmon tannin on cholesterol metabolism have yet to be fully understood. The present study investigated the regulation of persimmon tannin on the expression of genes critical for cholesterol absorption and cholesterol efflux. Our results indicated that persimmon tannin reduced the uptake of 22-NBD-cholesterol and inhibited the accumulation of cholesterol significantly in HepG2 and Caco-2 cell lines. The mRNA and proteins were quantified using real time PCR and western blot, respectively. The expression of SREBP-2 gene, critical for cholesterol synthesis, and NPC1L1 involved in cholesterol absorption were significantly inhibited by persimmon tannin. Moreover, persimmon tannin showed potential in promoting cholesterol efflux through up-regulating mRNA and/or protein levels of ABCA1, ABCG1, SR-BI, CYP7A1 and ABCG5/G8. However, the regulation effects of persimmon tannin on cholesterol homeostasis in both cell lines were LXRα independent.

•The tested compounds inhibit 22-NBD-cholesterol cellular accumulation via suppression of NPC1L1 expression.•A-type ECG and EGCG dimers inhibited cholesterol accumulation at low transport ratios.•Both paracellular and transcellular pathways were involved in the transportation of the tested compounds.The hypocholesterolaemic activities of EC, ECG, EGCG and their corresponding A-type dimers (A-type EC, ECG and EGCG dimers) were investigated in Caco-2 cell monolayer model. Among them, A-type ECG and EGCG dimers are the unique units of persimmon proanthocyanidins and few information about their bioavailability is available. The data showed that all of these six phenols could inhibit fluorescent 22-NBD-cholesterol cellular accumulation significantly (P < 0.01) through suppression of NPC1L1 gene expression which is related with cholesterol absorption. The further data demonstrated that the cholesterol-lowering activities of the six compounds were also involved with their chemical structures and permeability in Caco-2 monolayers. Additionally, we found that all of the tested compounds were the substrates of P-gp and tight junctions could limit the bioavailability of these compounds. These are also the first data concerning the permeability of A-type ECG and EGCG dimers across Caco-2 cell monolayer.

•Five proanthocyanidin dimers were obtained by depolymerizing PT40 using (+)-catechin and EGCG as chain breakers.•Three dimer analogues with the C-ring-opened structural unit were tentatively identified and reported for the first time.•The formation of the C-ring-opened diaryl-propan-2-gallate unit on dimer analogues enhanced their antioxidant potency.This study aimed to establish an approach for preparing new representative proanthocyanidin oligomers from persimmon for further structure−activity relationship study. Persimmon tannins (with a mean degree of polymerization of 23.7) were depolymerized, using 0.1 M methanolic HCl, with (+)-catechin and (−)-epigallocatechin gallate as chain breakers. Normal phase high-performance liquid chromatography (NP−HPLC) coupled with reversed phase high-performance liquid chromatography mass spectrometry (RP−HPLC−MS) method was used to analyse the degradation products. Four B-type and one A-type dimers were tentatively identified. In addition, three dimer analogues, 1-(3′,4′-dihydroxyphenyl)-3-(2′′,4′′,6′′-trihydroxyphenyl)propan-2-ol-(epi)catechin dimer (B-type) and 1-(3′,4′,5′-trihydroxyphenyl)-3-(2′′,4′′,6′′-trihydroxyphenyl)-propan-2-gallate-(epi)gallocatechin-3-gallate dimers (A- and B-type), were reported for the first time. Three different assays were employed to evaluate the antioxidant capacities of the new dimer analogues. Our results revealed that the formation of the C-ring-opened diaryl-propan-2-gallate structural unit on dimer analogues enhanced their antioxidant abilities in aqueous systems for the first time. This research provided a workable approach for preparing novel dimeric proanthocyanidins for further structure–activity relationship study.

Proanthocyanidins (PAs) have been widely recognized for their broad spectrum of beneficial health effects, which are highly structure-dependent. It was found that PA dimers epicatechin-3-gallate-(4β→8,2β→O→7)-epicatechin-3-gallate (A-type ECG dimer) and epigallocatechin-3-gallate-(4β→,2β→O→7)-epigallocatechin-3-gallate (A-type EGCG dimer) inhibit the differentiation of 3T3-L1 cells significantly, whereas epicatechin-(4β→8,2β→O→7)-epicatechin (A-type EC dimer) and epicatechin-(4β→8)-epicatechin (B-type EC dimer) showed little effect in previous work. However, the underlying mechanisms are unclear. To test whether bilayer perturbation may underlie this diversity of actions, we examined the bilayer-modifying effects of the four dimers in both 3T3-L1 cell and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine liposome models by using scanning electron microscopy, fluorescent spectroscopy, differential scanning calorimetry, and molecular dynamics methods. Our results revealed that A-type ECG and EGCG dimers had a high affinity for the lipid bilayer and could form simultaneous hydrogen bonds (H-bond) with both the surface oxygen acceptors and the deeper inside lipid oxygen atoms. However, A-type and B-type EC dimers contacted only the surface oxygen atoms with limited and significantly fewer H-bonds. A-type ECG and EGCG dimers notably distorted the membrane morphology of 3T3-L1 cells. In the present study, we found there was a high positive correlation between the membrane-disturbing abilities of the four dimers and their 3T3-L1 cell differentiation inhibitory effects as previously reported. This indicated that the strong 3T3-L1 cell differentiation inhibitory effect of A-type ECG and EGCG dimers might be due to their strong bilayer-perturbing potency.Keywords: A-type ECG and EGCG dimers; bilayer perturbing potency; correlation; differentiation inhibition; molecular dynamics simulation;

•Three phenolic compounds from longan seed extract are identified for the first time.•Different assays are used to confirm their antioxidant activities.•The three newly characterized compounds were the main contributors to the antioxidant activity of longan seeds.Polyphenols have been shown to be the main active components responsible for the antioxidant effect of longan seed extract. To figure out the structure–activity relationships of the major phenolic constituents isolated from longan seeds, structural elucidation and antioxidant activities of these compounds were investigated. The detailed structures of three phenolic compounds, namely 9-O-(3-carboxymethyl-4-(p-formylstyryl))hydroxybutanoic acid, 2-hydroxy-3-methoxycaffeic acid 5-O-β-d-glucopyranoside and 3′-O-methyl-4′-O-(4-O-galloyl-α-l-rhamnopyranosyl)ellagic acid, were elucidated for the first time from longan seeds by nuclear magnetic resonance (NMR), Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR–MS) and other spectroscopic methods. The antioxidant activities of the three compounds as well as four previously reported compounds including corilagin, (S)-flavogallonic acid, 3′-O-methylellagic acid 4′-O-β-d-glucopyranoside and ethyl gallate were compared in three different assays including the Trolox equivalent antioxidant capacity (TEAC) assay, the oxygen radical absorbance capacity (ORAC) assay and the β-carotene–linoleate model assay. Our results confirmed that the previously uncharacterized 2-hydroxy-3-methoxycaffeic acid 5-O-β-d-glucopyranoside and 3′-O-methyl-4′-O-(4-O-galloyl-α-l-rhamnopyranosyl)ellagic acid were the main contributors to the potent activity of longan seed extract.

Metabolism of B-type EC dimer, A-type EC dimer, A-type ECG dimer, and A-type EGCG dimer was compared in vitro after incubation with rat intestinal microbiota for 0–24 h. A “dimeric” catabolite (m/z 815.6) was detected in four procyanthocyanidin dimers. Although the early cleavage of the C4–C8 interflavan bond and the reductive cleavage of the C-ring occurred in both B-type and A-type dimers, the degradation routes of these two types of dimers might somewhat differ. A dimeric catabolite C1 and more low molecular weight phenolic acids were detected in the metabolites of A-type EC dimer, but not in B-type EC dimer. The antioxidant capabilities of the A-type dimers were enhanced significantly after incubation for 6 h, whereas the antioxidant capacity of B-type EC dimer decreased. The results suggested that changes in antioxidant activity of procyanidin dimers after bioconversion by rat intestinal microbiota were not only structure dependent but also incubation condition dependent.

The degradation behaviors of four different proanthocyanidins dimers including B-type (e)picatechin (E)C dimer and A-type (epi)catechin (E)C dimer, A-type (epi)catechin-3-O-gallate (E)CG dimer and A-type (epi)gallocatechin-3-O-gallate (E)GCG dimer as affected by pH and temperature were compared in this study. The results showed that the stability of proanthocyanidins dimers was not only temperature and pH dependent, but also structure dependent. Proanthocyanidins dimers were found to be unstable at pH as low as 1.5 and physiological pH conditions, and they were rather unstable at alkaline conditions and temperature above 25 °C. Among the four dimers tested, B-type (E)C dimer was the least stable, while A-type (E)C dimer was the most stable. In general, B-type dimers showed less stability than A-type ones. The higher the degree of galloylation and the more the hydroxyl groups in the molecular, the less stable the proanthocyanidins dimers.

•Persimmon tannin (PT) inhibited lipid accumulation in L02 cells.•PT inhibited L02 cells lipid accumulation by targeting miR-122 and miR-33b.•A-type ECG and EGCG dimer structural subunits served as the basis for the inhibition.Our previous study showed that persimmon tannin was the main active component being responsible for the anti-hyperlipidemic effect of persimmon extract, but the underlying molecular mechanisms were unclear. This study aimed to evaluate the effects of persimmon tannin on hepatic lipid accumulation in L02 cells and the underlying mechanisms, as well as the structure–activity relationships. Persimmon tannin significantly reduced L02 cellar lipid accumulation, similar effects were observed in the cells treated with its two characteristic structural subunits A-type ECG dimers and A-type EGCG dimer. Furthermore, the expression of miR-122 and miR-33b and their target genes were also suppressed by persimmon tannin, A-type ECG and A-type EGCG dimer. These results indicated that persimmon tannin improved hepatic steatosis through regulating miR-122 and miR-33b. The characteristic structural subunits A-type ECG and A-type EGCG dimer served as the basis for the inhibition of persimmon tannin on free fatty acid induced steatosis in L02 cells.

The present study was to investigate whether high molecular weight persimmon tannin (HMWPT) is the main component associated with the anti-hyperlipidemic effect of consuming persimmon and its underlying mechanism. Male wistar rats were given a basic diet (control), a high-fat diet, a high-fat diet plus 0.5% of HMWPT or 4.2% of lyophilized fresh persimmon fruit (with the same diet HMWPT content in the two groups) for 9 weeks. Administration of HMWPT or persimmon fruit significantly (p < 0.05) lowered serum triglycerides and free fatty acids, enhanced the excretion of triglycerides, cholesterol and bile acids, and improved hepatic steatosis in rats fed a high-fat diet. Dietary HMWPT or persimmon fruit significantly decreased the protein levels of fatty acid synthase (FAS), and stimulated AMP-activated protein kinase (AMPK) phosphorylation and down-regulated genes involved in lipogenesis, including transcriptional factor sterol regulatory element binding protein 1 (SREBP1) and acetyl CoA carboxylase (ACC). In addition, the expression of proteins involved in fatty acid oxidation, such as carnitine palmitoyltransferase-1 (CPT-1), was notably up-regulated. Furthermore, HMWPT and persimmon fruit suppressed inflammatory cytokines such as tumor necrosis factor α (TNFα) and C-reactive protein (CRP) and the protein level of nuclear factor-kappa B (NFκB) in the liver. Taken together, our findings demonstrated that HMWPT reproduced the anti-hyperlipidemic effects of persimmon fruit, and was a pivotal constituent of persimmon fruit accounting for prevention of liver steatosis and its progression to nonalcoholic steatohepatitis (NASH) by activation of the AMPK and regulation of its downstream targets, suppressing NF-κB activation and inflammatory responses, and inhibiting lipids and bile acid absorption.

To figure out the key phenolic compounds accounting for the antioxidant effects of longan (Dimocarpus longan Lour.) seed extract, online fishing/knockout method, activity evaluation assays, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR–MS), and high-performance liquid chromatography electrospray ionization mass spectrometry (HPLC–ESI–MS) analysis were used jointly for the first time. p-Coumaric acid–glycoside, (S)-flavogallonic acid, ellagic acid derivative, and methyl-ellagic acid glucopyranoside were first identified in longan seeds. In addition, our study revealed that ellagic acid as well as its derivative and p-coumaric acid–glycoside had important contribution to the potent antioxidant activity of longan seed extract, while gallic acid, corilagin, (S)-flavogallonic acid, methyl-ellagic acid glucopyranoside, and ethyl gallate showed very little contribution to the total antioxidant activity of longan seed extract. The combining use of the online fishing/knockout method, activity evaluation assays, FT-ICR–MS, and HPLC–ESI–MS analysis is a useful and simple strategy for screening of key bioactive compounds from complex extracts.

MALDI-TOF MS suggested that the high molecular weight proanthocyanidin (condensed tannin) from persimmon (Diospyros kaki L.) pulp comprised a heteropolyflavanol series with flavan-3-O-galloylated extenders, flavan-3-ol and flavonol terminal units, and A-type interflavan linkages. Thiolysis-HPLC-ESI-MS with DAD, electrochemical, and ESI-MS detection confirmed a previously unreported terminal unit, the flavonol myricetin, in addition to the typical flavan-3-ols catechin and epigallocatechin gallate. The extender units were epicatechin, epigallocatechin, (epi)gallocatechin-3-O-gallate, and (epi)catechin-3-O-gallate. The crude tannin had a high prodelphinidin content (65%) and a high degree of 3-O-galloylation (72%). The material was fractionated on Toyopearl TSK-HW-50-F to yield fractions distinguished by degree of polymerization (DP). Thiolysis suggested that the persimmon tannin was composed of polymers ranging from 7 to 20 kDa (DP 19−47), but sizes estimated by GPC were 50−70% smaller. The crude material was chemically degraded with acid to yield products that were amenable to NMR and ESI-MS analysis, which were used to establish for the first time that persimmon tannin has a mixture of B-type and A-type linkages.

The effects of four proanthocyanidin dimers including epicatechin-(4β→8, 2β→O→7)-epicatechin (A-type EC dimer), epicatechin-(4β→8)-epicatechin (B-type EC dimer), epicatechin-3-gallate-(4β→8, 2β→O→7)-epicatechin-3-gallate (A-type ECG dimer) and epigallocatechin-3-gallate-(4β→8, 2β→O→7)-epigallocatechin-3-gallate (A-type EGCG dimer) on 3T3-L1 preadipocyte cell differentiation and the underlying mechanisms were explored and compared. The results showed that A-type ECG dimer and A-type EGCG dimer significantly reduced the intracellular lipid accumulation in 3T3-L1 preadipocyte cells by targeting miR-27a and miR-27b as well as peroxisome proliferator-activated receptor γ (PPARγ) in the early stage of differentiation, while A-type EC dimer and B-type EC dimer showed little effect. In addition, our results revealed that the inhibitory effects of proanthocyanidin dimers on 3T3-L1 preadipocyte differentiation were highly structure-dependent and the effects were associated with the dimer–membrane interactions. The presence of galloyl moieties and A-type linkage within the structure of proanthocyanidins might be crucial for their inhibitory effect on adipogenesis. The strong disturbing effects of A-type ECG and A type EGCG dimers on the fluidity, hydrophobicity and permeability of membrane of 3T3-L1 preadipocyte cell were at least, in part, responsible for their distinct inhibitory effects on adipocyte hyperplasia.

•A-type EGCG dimer and A-type ECG dimer inhibited PLA2 mostly.•A-type EGCG and ECG dimer units are structural requirements for inhibiting PLA2.•Other residues such as Trp18, Try27, Gly29, His47 and Tyr63 are involved in the interactions.To more fully understand the mechanism by which persimmon tannin (PT) inhibited phospholipase A2 (PLA2) and the structural requirements of PT for the inhibition, the interactions between PLA2 and seven characteristic structural elements of PT including epigallocatechin-3-gallate (EGCG), myricetin, epicatechin-3-gallate (ECG), epicatechin-3-gallate-(4β → 8, 2β → O → 7)-epicatechin-3-gallate (A-type ECG dimer), epigallocatechin-3-gallate-(4β → 8, 2β → O → 7)-epigallocatechin-3-gallate (A-type EGCG dimer), epicatechin-(4β → 8, 2β → O → 7)-epicatechin (A-type EC dimer) and epicatechin-(4β → 8)-epicatechin (B-type EC dimer) were studied by enzymatic and spectroscopic methods. Molecular docking was also used to explore the possible residues involved in the interactions. The results revealed that A-type EGCG dimer and A-type ECG dimer showed higher inhibitory effects on the catalytic activity of PLA2 than monomers and B-type dimer. They induced greater conformational changes in PLA2 than other structural elements. In addition, molecular docking studies revealed that expect for lysine residues, other residues such as Trp18, Try27, Gly29, His47 and Tyr63 were involved in the interactions. We propose that A-type EGCG and ECG dimer units may be structural requirements for the interaction between PT and PLA2. Our data provide an additional structural basis for anti-PLA2 activity of persimmon tannin.Download full-size image