茶多酚对ApoE~(-/-)小鼠肠道菌群多样性的影响

目的以高脂饲料饲养的SPF级C57 BL/6 ApoE-/-小鼠作为动物模型,研究茶多酚采食对其肠道菌群多样性的影响。方法通过随机饮水的方式给予ApoE-/-小鼠0.4、0.8和1.6 g/L的茶多酚,处理14 d时用PCR-DGGE分析对照组(CK)和茶多酚组小鼠新鲜粪便中肠道菌群的相似性和多样性。结果 UPGMA聚类分析表明,低剂量茶多酚组(LTP)、中剂量茶多酚组(MTP)这两组与对照组(CK)、高剂量茶多酚组(HTP)聚为两大簇。PCA分析显示,LTP组与CK组、MTP组、HTP组分别聚集在不同位置,有明显界限;多样性数据分析显示:CK组DGGE图谱的丰富度和Shannon-Wiener指数(H')与茶多酚组差异无统计学意义(P0.05);CK组与MTP组的均匀度(E)差异存在统计学意义(P0.05,P=0.015),说明中剂量茶多酚作用14 d后与对照组肠道菌群的菌群分配相比均一性显著下降。结论连续处理14 d时CK组与LTP组、MTP组小鼠肠道菌群差异有统计学意义,即茶多酚对ApoE-/-小鼠肠道菌群多样性有显著影响。     

Design,synthesis and biological evaluation of small molecular polyphenols as entry inhibitors against H5N1

To find novel compounds against H₅N₁, three series of known or novel small molecular polyphenols were synthesized and tested in vitro for anti-H₅N₁ activity. In addition, the preliminary structure–antiviral activity relationships were elaborated. The results showed that some small molecular polyphenols had better anti-H₅N₁ activity, and could serve as novel virus entry inhibitors against H₅N₁, likely targeting to HA2 protein. Noticeably, compound 4a showed the strongest activity against H₅N₁ among these compounds, and the molecular modeling analysis also suggested that this compound might target to HA2 protein. Therefore, compound 4a is well qualified to serve as a lead compound or scaffold for the further development of H₅N₁ entry inhibitor.     

The apple FERONIA receptor-like kinase MdMRLK2 negatively regulates Valsa canker resistance by suppressing defence responses and hypersensitive reaction

Valsa canker, caused by the fungus Valsa mali, is one of the most destructive diseases of apple trees in China and other East Asian countries. The plant receptor-like kinase FERONIA is involved in plant cell growth, development, and immunity. However, little is known about the function of FERONIA in apple defence against V. mali. In this study, we found that MdMRLK2 was highly induced by V. mali in twigs of V. mali-susceptible Malus mellana but not in those of the resistant species Malus yunnaensis. 35S:MdMRLK2 apple plants showed compromised resistance relative to wild-type (WT) plants. Further analyses indicated that 35S:MdMRLK2 apple plants had enhanced abscisic acid (ABA) levels and reduced salicylic acid (SA) levels relative to the WT on V. mali infection. MdMRLK2 overexpression also suppressed polyphenol accumulation and inhibited the activities of phenylalanine ammonia-lyase (PAL), β-1,3-glucanase (GLU), and chitinase (CHT) during V. mali infection. Moreover, MdMRLK2 interacted with MdHIR1, a hypersensitive-induced response protein, and suppressed the MdHIR1-mediated hypersensitive reaction (HR), probably by impairing MdHIR1 self-interaction. Collectively, these findings demonstrate that overexpression of MdMRLK2 compromises Valsa canker resistance, probably by (a) altering ABA and SA levels, (b) suppressing polyphenol accumulation, (c) inhibiting PAL, GLU, and CHT activities, and (d) blocking MdHIR1-mediated HR by disrupting MdHIR1 self-interaction.     

TRANSFORMATION AND ALLELOPATHY OF NATURAL DISSOLVED ORGANIC CARBON AND TANNIC ACID ARE AFFECTED BY SOLAR RADIATION AND BACTERIA1

The aim of this study was to test whether abiotic and biotic factors may affect allelopathic properties. Therefore, we investigated how solar radiation and bacteria influence allelopathic effects of the plant‐derived, polyphenolic tannic acid (TA) on microalgae. Using a block design, lake water samples with and without TA were exposed to solar radiation or kept in darkness with or without bacteria for 3 weeks. Dissolved organic carbon (DOC), specific size fractions of DOC analyzed by chromatography–organic carbon detection (LC‐OCD), and concentrations of total phenolic compounds (TPC) were measured to follow the fate of TA in lake water with natural DOC exposed to photolytic and microbial degradation. DOC and TPC decreased in dark‐incubated lake water with TA and bacteria indicating microbial degradation. In contrast, exposure to solar radiation of lake water with TA and bacteria did not decrease DOC. Chromatographic analyses documented an accumulation of DOC mean size fraction designated as humic substances (HS) in sunlit water samples with TA. The recalcitrance of the humic fraction indicates that photolytic degradation may contribute to a DOC less available for bacterial degradation. Subsequent growth tests with Desmodesmus armatus (Chodat) E. Hegewald showed low but reproducible difference in algal growth with lower algal growth rate cultured in photolytically and microbially degraded TA in lake water than cultured in respective dark treatments. This finding highlights the importance of photolytic processes and microbial degradation influencing allelopathic effects and may explain the high potential of allelochemicals for structuring the phytoplankton community composition in naturally illuminated surface waters.     

Plant polyphenols mobilize endogenous copper in human peripheral lymphocytes leading to oxidative DNA breakage: a putative mechanism for anticancer properties

Plant polyphenols are important components of human diet and a number of them are considered to possess chemopreventive and therapeutic properties against cancer. They are recognized as naturally occurring antioxidants but also act as prooxidants catalyzing DNA degradation in the presence of transition metal ions such as copper. Using human peripheral lymphocytes and Comet assay we have previously confirmed that resveratrol-Cu(II) is indeed capable of causing DNA degradation in cells. In this paper we show that the polyphenols alone (in the absence of added copper) are also capable of causing DNA breakage in cells. Incubation of lymphocytes with neocuproine inhibited the DNA degradation confirming that Cu(I) is an intermediate in the DNA cleavage reaction. Further, we have also shown that polyphenols generate oxidative stress in lymphocytes which is inhibited by scavengers of reactive oxygen species and neocuproine. These results are in further support of our hypothesis that anticancer mechanism of plant polyphenols involves mobilization of endogenous copper, possibly chromatin bound copper, and the consequent prooxidant action.     

Radioprotective properties of apple polyphenols: An in vitro study

Present study was undertaken to evaluate the radioprotective ability of total polyphenols extracted from edible portion (epicarp and mesocarp) of apple. Prior administration of apple polyphenols to murine thymocytes significantly countered radiation induced DNA damage (evaluated by alkaline halo assay) and cell death (trypan blue exclusion method) in a dose dependent manner maximally at a concentration of 2 and 0.2 mg/ml respectively. Apple polyphenols in a dose dependent fashion inhibited both radiation or Fenton reaction mediated 2-deoxyribose (2-DR) degradation indicating its ability to scavenge hydroxyl radicals and this activity was found to be unaltered in presence of simulated gastric juice. Similarly apple polyphenols in a dose dependent fashion scavenged DPPH radicals (maximum 69% at 1 mg/ml), superoxide anions (maximum 88% at 2 mg/ml), reduced Fe^{3 +} to Fe^{2 +} (maximum at 1 mg/ml) and inhibited Fenton reaction mediated lipid peroxidation (maximum 66% at 1.5 mg/ml) further establishing its antioxidative properties. Studies carried out with plasmid DNA revealed the ability of apple polyphenols to inhibit radiation induced single as well as double strand breaks. The results clearly indicate that apple polyphenols have significant potential to protect cellular system from radiation induced damage and ability to scavenge free radicals might be playing an important role in its radioprotective manifestation.     

Suppression of Met activation in human colon cancer cells treated with (−)-epigallocatechin-3-gallate: Minor role of hydrogen peroxide

Colorectal cancer is the second leading cause of cancer-related deaths in the U.S. Met, the receptor for hepatocyte growth factor (HGF), is over-expressed in colon tumors and is associated with poor prognosis. Recently, the green tea polyphenol (−)-epigallocatechin gallate (EGCG) was reported to suppress Met activation in breast cancer cells. However, the possible confounding effect of hydrogen peroxide (H₂O₂), produced when EGCG is added to cell culture media, was not assessed. In the present study, the human colon cancer cell lines HCT116 and HT29 were used to examine the relationships between Met activation, EGCG treatment, and H₂O₂ generation. At concentrations of 0.5, 1, and 5 μM, EGCG suppressed markedly the activation of Met in the presence of HGF. Concentrations of 10 μM EGCG and below generated low amounts of H₂O₂ (<1.5 μM), whereas higher H₂O₂ concentrations (>5 μM) were required to directly increase the phosphorylation of Met. Moreover, suppression of Met activation by EGCG occurred in the presence or absence of catalase, suggesting that such effects were not an ‘artifact’ of H₂O₂ generated from EGCG in cell culture media. We conclude that EGCG might be a beneficial therapeutic agent in the colon, inhibiting Met signaling and helping to attenuate tumor spread/metastasis, independent of H₂O₂-related mechanisms.     

苦茶Camellia assamica var.kucha茶多酚的HPLC-DAD/MS分析

苦茶是一种特殊的茶组植物,它以1,3,7,9-四甲基尿酸为主要的嘌呤生物碱。本文采用高效液相色谱-二极管阵列检测/质谱联用(HPLC-DAD/MS)的方法对苦茶水提液中的茶多酚和嘌呤生物碱进行了定性分析,检测到3种嘌呤生物碱、7种儿茶素类化合物和2种非儿茶素类茶多酚(没食子酰奎宁酸酯和咖啡酰奎宁酸酯)。同时与传统绿茶在儿茶素类化合物的组成和含量上进行了比较,结果显示,苦茶中总儿茶素含量(13.82%)远高于传统绿茶(7.37%),但各儿茶素类化合物的相对组成比在两种茶中极其相近,均以酯型儿茶素为主。