Diet and Health: Apple Polyphenols as Antioxidants

The traditional American rhyme says, “an apple a day keeps the doctor away.” What has made apples exceptional and appreciated for a million years? Besides their content of pectin, vitamins and minerals, they are considered to be a good source of antioxidants that scavenge and neutralize free radicals, which in turn play a role in the onset of cardiovascular diseases and cancers. Polyphenols are major antioxidants in apples, however, the antioxidants vary with the apple variety, and the post-harvest storage conditions. Further, the polyphenols are distributed differently throughout the fruit (skin or flesh). The paper reviews the present knowledge on apple polyphenols, their bioavailability and pro-health functionality.     

Red Wine Polyphenols for Cancer Prevention

Conventional cancer therapies, the second leading cause of death worldwide, result in serious side effects and, at best, merely extend the patient''s lifespan by a few years. Searching for effective prevention is of high priority in both basic and clinical sciences. In recent decades natural products have been considered to be an important source of cancer chemopreventive agents. Red wine polyphenols, which consisted of various powerful antioxidants such as flavonoids and stilbenes, have been implicated in cancer prevention and that promote human health without recognizable side effects. Since resveratrol, a major component of red wine polyphenols, has been studied and reviewed extensively for its chemopreventive activity to interfere with the multi-stage carcinogenesis, this review focuses on recent progress in studies on cancer chemopreventive activities of red wine polyphenol extracts and fractions as well as other red wine polyphenols, like procyanidin B5 analogues and myricetin.     

Biflavonoid-Induced Disruption of Hydrogen Bonds Leads to Amyloid-β Disaggregation

Deposition of amyloid β (Aβ) fibrils in the brain is a key pathologic hallmark of Alzheimer’s disease. A class of polyphenolic biflavonoids is known to have anti-amyloidogenic effects by inhibiting aggregation of Aβ and promoting disaggregation of Aβ fibrils. In the present study, we further sought to investigate the structural basis of the Aβ disaggregating activity of biflavonoids and their interactions at the atomic level. A thioflavin T (ThT) fluorescence assay revealed that amentoflavone-type biflavonoids promote disaggregation of Aβ fibrils with varying potency due to specific structural differences. The computational analysis herein provides the first atomistic details for the mechanism of Aβ disaggregation by biflavonoids. Molecular docking analysis showed that biflavonoids preferentially bind to the aromatic-rich, partially ordered N-termini of Aβ fibril via the π–π interactions. Moreover, docking scores correlate well with the ThT EC₅₀ values. Molecular dynamic simulations revealed that biflavonoids decrease the content of β-sheet in Aβ fibril in a structure-dependent manner. Hydrogen bond analysis further supported that the substitution of hydroxyl groups capable of hydrogen bond formation at two positions on the biflavonoid scaffold leads to significantly disaggregation of Aβ fibrils. Taken together, our data indicate that biflavonoids promote disaggregation of Aβ fibrils due to their ability to disrupt the fibril structure, suggesting biflavonoids as a lead class of compounds to develop a therapeutic agent for Alzheimer’s disease.     

分子修饰法制备油溶性茶多酚及其抗氧化性能的研究

采用分子修饰法制备了豆油脂肪酸酐修饰的茶多酚,通过红外光谱对分子修饰的茶多酚进行了结构表征。将修饰后的茶多酚作为油脂的抗氧化剂,添加到豆油中,考察其溶解性及抗氧化性能。结果表明,有机基团修饰的茶多酚具有优良的分散性,可提高豆油的抗氧化性能。在相同浓度时,豆油脂肪酸酐修饰的茶多酚抗氧化活性优于茶多酚和BHT。     

Antioxidant properties and composition of Majorana syriaca extracts

Majorana syriaca is an important food‐flavouring ingredient in the Middle Eastern culture known commonly as Za'atar. The components of the plant were extracted in a Soxhlet apparatus sequentially with solvents of increasing polarity, specifically with petroleum ether (P), diethyl ether (D), ethyl acetate (EAc), and ethanol (E). The activity of the extracts to scavenge the 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH^?) followed the order D > E > EAc > P. Moreover, the antioxidant activity in corn oil at concentrations of 200, 500 and 1000 ppm was monitored through peroxide value and conjugated hydroperoxide measurements and revealed that D and E extracts resulted in the highest protection followed by EAc and P extracts. Increasing the concentration from 200 to 500 ppm depressed peroxide formation, while a further increase had no effect. The main components of the P extract according to GS‐MS analysis were thymol (42.89%) and carvacrol (42.75%). The remaining extracts comprise flavonoids and phenolic acids that provide the antiradical and antioxidant activity.     

气相色谱法测定茶多酚中的氯仿和乙酸乙酯残留

以正已烷为萃取剂,对茶多酚(TP)水溶液进行萃取,用气相色谱法分析了TP溶液中的残迹物氯仿和乙酸乙酯。色谱柱为2m×3mmi.d.不锈钢填充柱,固定相为10%的PEG20M,载体为ChromosorbW/WA。氯仿和乙酸乙酯的回收率分别为96.7%～104.3%和98.5%～103.6%;相对标准偏差分别为3.5%和1.7%;最低检测限分别为0.50ug/和0.36ug/g。     

食品中多酚类化合物测定方法研究进展

食品中的多酚类化合物主要来自于植物源性食品,人们在研究和开发各种食品时就不可避免的要对食品中的多酚类化合物进行分析与测定.目前应用于食品多酚类化合物的测定方法主要有高锰酸钾滴定法、光谱分析测定法、色谱分析测定法等,是对食品中多酚类化合物分析的必要手段之一.主要对这几种测定方法进行简介和比较,为以后食品中的多酚类化合物研究提供参考.     

超滤膜澄清分离速溶茶副产品中茶多酚的研究

研究了浓度、温度、压力各因素对截留分子量100k超滤膜澄清分离速溶茶副产品中茶多酚的影响,并采用正交试验设计优化了超滤膜澄清分离的工艺条件.结果表明,在样液质量分数0.40%、温度35℃、压力0.138 MPa的条件下分离试样,膜透过液中茶多酚含量达48.73%,得率为40.75%,说明超滤技术是澄清分离速溶茶副产品中茶多酚的有效手段之一.     

纳滤浓缩绿茶提取液的研究和浓缩模型

研究了绿茶提取液的纳滤浓缩分离过程,采用两种操作方式:连续式浓缩和间歇式浓缩.在连续式浓缩实验中,通过测定不同操作压力下透过实验所得的通量、水脱除率和对茶多酚的截留率来分析纳滤过程的特点,在0.4~0.8 MPa下对茶多酚的平均截留率为97.3%.在间歇式浓缩实验中,测定了膜对不同茶水比浸取所得茶汤的截留性能,实验值与浓缩模型预测值进行了比较,实测值与模型值吻合较好,表明浓缩模型对于茶多酚的纳滤浓缩分离过程具有较好的适用性,可用于浓缩过程的设计计算.     

淡竹叶多酚的提取纯化工艺优化、组分分析及体外抗氧化活性研究

目的 确定淡竹叶多酚提取纯化工艺,分析主要成分及体外抗氧化活性。方法 采用超声辅助提取淡竹叶多酚,通过响应面实验确定最佳提取条件。选取适合淡竹叶多酚纯化的大孔树脂,对纯化工艺参数进行优化。通过高效液相色谱-质谱法(high performance liquid chromatography-mass spectrometry, HPLC-MS)鉴定淡竹叶多酚的主要成分,并评价其体外抗氧化活性。结果 淡竹叶多酚的最佳提取工艺参数为:乙醇体积分数60%、超声功率500 W、料液比1:25 (g/mL)、超声时间24 min及超声温度59℃,该条件下淡竹叶多酚提取量为8.01 mg/g。淡竹叶多酚纯化工艺参数为:上样质量浓度6 mg/mL、pH 4、流速2 mL/min、解吸液为70%乙醇、解吸体积90 mL,纯化后的淡竹叶多酚纯度由12.86%提高到76.18%。通过HPLC-MS鉴定出16种酚类成分,且纯化后多酚有较高的抗氧化活性。结论 本研究得到了淡竹叶多酚提取纯化工艺,得到的多酚纯化物有明显的抗氧化活性。