Search

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. [ABSTRACT FROM AUTHOR]

Use of gallic acid (GA) as a standard in the Folin-Ciocalteu assay leads to an underestimation of phenol content in persimmon extracts so does the widely used catechin (C) in vanillin assay for determining condensed tannins in persimmon extracts. To develop suitable standards for addressing the issue of accuracy, we prepared highly purified persimmon tannin (PT) and its three fractions (PT20, PT40 and PT60), as well as three characteristic structural subunits of PT including 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) and epicatechin-(4β → 8)-epicatechin (B-type EC dimer). We compared the color yield of commercially available standards including the dimers GA, EGCG, ECG, C and PT and its three fractions in the Folin-Ciocalteu assay and vanillin assay, respectively. Our results suggested that for estimating phenol content in persimmon extracts, EGCG, ECG, C and GA were poor standards in Folin-Ciocalteu assay. We recommended PT40 as the most suitable standard in determining the phenol content of persimmon extracts. In the vanillin assay, A-type EGCG dimer or A-type ECG dimer were superior than the commonly used C as standards, and ECG was also an alternative when A-type EGCG dimer or A-type ECG dimer were not available. [ABSTRACT FROM AUTHOR]

The aim of this work was to compare the efficiency of different carrier agents (maltodextrin, gum arabic, starch sodium octenyl succinate, whey protein concentrate, and egg albumin) on the powder recovery and physicochemical properties of persimmon powders produced by spray drying. Moisture content, water activity, hygroscopicity, solubility index, total phenol retention, color parameters, particle size, morphology, crystalline state, and sorption isotherms of persimmon powders were determined. No powder was recovered when the persimmon pulp was spray dried alone. The amount of maltodextrin, gum arabic, starch sodium octenyl succinate, whey protein concentrate, and egg albumin needed to obtain a powder recovery of 70% was 45, 30, 30, 25, and 10%, respectively. The use of maltodextrin, gum arabic, and starch sodium octenyl succinate resulted in higher total polyphenol retention and better reconstitution properties, but the powders were paler than those with whey protein concentrate and egg albumin. All carriers could aid the formation of persimmon irregular spherical microcapsules. However, powders produced with maltodextrin and gum arabic had a smoother surface and a more spherical shape than powders produced with other carriers. In addition, powders produced with starch sodium octenyl succinate, whey protein concentrate, and egg albumin were more agglomerated and shriveled compared to those produced with maltodextrin and gum arabic. All experimental data of water adsorption were well fitted to the Guggenheim-Anderson-de Boer (GAB) model. [ABSTRACT FROM AUTHOR]

Abstract: To elucidate the anti-venom mechanism of persimmon tannin, the interaction between a polymeric persimmon proanthocyanidin fraction (PT40) and phospholipase A2 (PLA2) or bovine serum albumin (BSA) were studied using a competitive binding assay and spectroscopic methods including Fourier transform infrared spectroscopy (FT-IR), circular dichroism (CD), and resonance light scattering (RLS) spectroscopy. The results revealed that PT40 has a higher affinity for PLA2 than for BSA at physiological pH and induced greater conformational changes in PLA2 than in BSA. PT40 covalently bound to PLA2 in a reaction probably involving Lys residues. We propose that the high affinity of PT40 for PLA2 and the covalent modification of PLA2 by PT40 may be responsible for the ability of the tannin to irreversibly inhibit PLA2 catalytic activity, to prevent edema, and to neutralize the lethality of Chinese cobra PLA2 in vivo. [Copyright &y& Elsevier]

Abstract: Aimed to elucidate whether high molecular weight persimmon tannin (HMWPT) is responsible for the hypolipidemic effect of consuming persimmon fruit, the effects of HMWPT on high-cholesterol diet fed rats were investigated. Male Sprague–Dawley rats were fed a 2% high-cholesterol diet and treated with different dosages of HMWPT or without HMWPT for 9weeks, lipids and antioxidant profiles were examined and the morphology of livers was checked as well. The results indicated that HMWPT effectively reduced serum and hepatic triglyceride, total cholesterol and low density lipoprotein cholesterol while increased the serum and hepatic high density lipoprotein cholesterol (p <0.05). In addition, 100mg/kg body weight per day of HMWPT treatment could significantly enhance the serum lecithin cholesterol acyl transferase (LCAT) activity and fecal bile acids excretion (p <0.05). Meanwhile, accumulation of hepatic lipid droplets and hepatic steatosis induced by high-cholesterol diet was inhibited markedly by HMWPT. Furthermore, high-cholesterol diet induced oxidative stress in rats but HMWPT significantly increased the decreased activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), elevated the lowered total anti-oxidation capability (T-AOC), (p <0.05), and decreased the raised malondialdehyde (MDA) levels (p <0.05) in serum or liver. These results suggested that HMWPT was responsible for the hypocholesterolemic effect of persimmon fruit and it might exert the hypolipidemic effect through stimulating serum LCAT activity, enhancing fecal bile acids excretion and improving antioxidant profile. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: To understand the anti-venom mechanism of persimmon tannin, the interaction between persimmon tannin (PT) and phospholipase A2 (PLA2) under physiological conditions was investigated by fluorescence quenching technique in combination with Fourier transform infrared (FT-IR) and circular dichroism (CD) spectra techniques. The results revealed that gradual fluorescence quenching was observed by titration of PLA2 (2.0μM) with increasing concentrations of PT (from 0 to 2.025μM), and the type of quenching was found to be a static quenching process. Stern–Volmer plots were not linear but had an intersection at C PT ≈1.0μM, indicating that PT binded to more than one class of sites on PLA2. The binding sites calculated on basis of Scatchard plots were about 2, supporting this result. The enthalpy change (ΔH) and entropy change (ΔS) of the binding sites were −17.44kJ/mol and 59.90kJ/mol·, separately, suggesting that hydrophobic interaction played a main role in the binding. In addition, synchronous fluorescence, FT-IR and CD spectra showed that dramatic conformational changes in PLA2 were induced by its interaction with PT. [Copyright &y& Elsevier]

Abstract: Mice were subcutaneously injected with d-galactose (d-gal, 150mg/kg per day) for 6weeks and were administered high molecular weight persimmon condensed tannin (HMWPT) simultaneously. After 6weeks of treatment, the animal behavior was observed in the open field test and water maze test, and the morphology of hippocampus and skin were checked. Meanwhile, the activities of antioxidant enzymes, the levels of non-enzymatic antioxidants, as well as malondialdehyde (MDA) were evaluated. The results indicated that HMWPT markedly inhibited the d-gal induced learning and memory impairment in both open field test and Morris water maze. Biochemical examination revealed that HMWPT significantly increased the decreased activities of superoxide dismutase (SOD), catalase (CAT), elevated the lowered total anti-oxidation capability (T-AOC), glutathione (GSH) and hydroxyproline (Hyp) contents (p <0.01 or p <0.05), and decreased the raised monoamine oxidase (MAO), total cholinesterase (TChE) activities and MDA level (p <0.01) in serum, liver or brain of aging mice induced by d-gal in a dose-dependent fashion. Furthermore, HMWPT significantly and (p <0.01) attenuated the d-gal induced number decrease, neuronal degeneration and karyopycnosis in cells in the hippocampus and decrease of thickness of skin epidermis and dermis. [Copyright &y& Elsevier]