杨梅素的半合成

以二氢杨梅素(DMY)为原料,经在碱性条件下开环和氧化成环反应半合成杨梅素,其结构经1H NMR,13C NMR和IR确证。在最佳反应条件[DMY 1.624 mmol,H2O(30 m L)为溶剂,依次加入15%H2O20.68 m L和16%Na OH溶液5.5 m L,于35℃反应24 h]下,收率16.21%。     

二氢杨梅素对高分子材料的抗氧化作用

通过差示扫描量热仪(DSC)和热失重分析仪(TGA)测定了二氢杨梅素(DMY)的热稳定性。测定了添加DMY的不同高分子材料的氧化诱导温度(OIT*),并与添加相同质量分数工业抗氧剂Irganox B215的样品进行了比较。实验结果表明,DMY在230℃以下稳定性良好,可用于加工温度低于230℃的各种高分子材料的加工过程,添加DMY的各种高分子材料的抗氧化性能优于添加Irganox B215的样品。对其抗氧化作用机理分析表明,DMY的特殊结构,特别是分子中羟基的数量和位置是其具有强抗氧剂性的根本原因。DMY无毒、高效,有望作为新型天然抗氧剂得到广泛应用。     

市售保健品中7种醒酒护肝功效成分的毛细管电泳测定

采用胶束电动毛细管电泳-二极管阵列检测器同时检测了市售保健品中儿茶素、表儿茶素、表没食子儿茶素、表儿茶素没食子酸酯、表没食子儿茶素没食子酸酯、二氢杨梅素和甘草酸等7种醒酒护肝功效成分.采用正交设计法对毛细管电泳条件[缓冲剂浓度、添加剂十二烷基硫酸钠(SDS)浓度、添加剂乙腈比例以及电泳缓冲溶液p H]进行了优化.在优化的条件下,7种组分在各自的线性范围内相关系数r≥0.9989,检出限和定量限分别为0.26~2.22μg/g(S/N=3)和0.87~7.39μg/g(S/N=10),日内精密度和日间精密度分别为1.3%~2.5%和1.9%~3.9%,样品加标回收率为91.4%~104.9%,加标样品的相对标准偏差(RSD)在1.4%~3.2%之间.本方法可在8 min内实现7种功效成分的同时检测,能够满足市售醒酒护肝产品的常规分析和质量评价要求.     

Graphene‐Nafion Composite Film Modified Electrode for Voltammetric Sensor for Determination of Dihydromyricetin

A simple but highly snesitive electrochemical sensor for the determination of dihydromyricetin (DMY) based on graphene‐Nafion nanocomposite film modified Glassy carbon electrode (GCE) was reported. The characteristic of the sensor was examined by scanning electron microscopic (SEM) and electrochemical impedance spectroscopy (EIS). Compares with bare GCE, pre‐anodized glassy carbon electrode (GCE(ox)) and Nafion modified electrode, the sensor exhibited the more superior ability of detecting DMY, due to the synergetic graphene and Nafion. Other, the dependence of the current on pH, instrumental parameters, accumulation time and potential were investigated to optimize the experimental conditions in the determination of DMY. Under the selected conditions, the response peak currents were linear relationship with the DMY concentrations in the range of 8.0 × 10^?8 ～ 2.0 × 10^?5 mol L^?1 with a detection limit of 2.0 × 10^?8 mol L^?1. And, the method was also applied successfully to detect DMY in Ampelopsis grossedentata samples.     

Structural properties of lecithin based reverse hexagonal (HII) liquid crystals and in vitro release of dihydromyricetin

Dihydromyricetin (DMY) was encapsulated to lecithin based reverse hexagonal (H_II) liquid crystals to improve its solubility limitation. PEG 400 was used as the representative oil phase. The H_II mesophases were identified by means of polarized light microscopy (POM) and small angle X-ray scattering (SAXS). The DMY was solubilized in interface layer inferred from the increase of the interfacial area of per surfactant a_s and the infrared spectra. The hexagonal samples showed highly elastic Maxwell properties and shear thinning properties indicated by their rheological spectra. Moreover with the decrease of PEG 400 content, the internal structure of samples apparently becomes more stable, as indicated by the increase in the storage and loss moduli and the decrease in a_s. Oleic acid enhances the viscoelasticity of sample and increases the release stability for DMY under acidic conditions. The in vitro release of DMY in H_II matrices showed that carriers have an ideal sustained release effect. The release of DMY was controlled by concentration diffusion.     

基于聚多巴胺的磁性纳米生物催化剂高效催化二氢杨梅素酰化

脂肪酶是一种三酰基甘油水解酶,目前广泛用于油脂化学、食品、有机合成和生物医药等领域.但是,游离脂肪酶在有机反应体系中容易失活,难以从反应体系中回收,导致其循环利用困难和生产成本增加.因此,需要对游离脂肪酶进行固定化,提高酶的稳定性和重复使用性,使其能够大规模用于工业生产.
　　磁性四氧化三铁纳米粒子(MNPs)具有其超顺磁性和大比表面积等性质,但MNPs需表面修饰才能进一步应用.近年来,仿生矿化法制备的聚多巴胺纳米材料受到人们关注.在仿生矿化过程中,单体多巴胺经自聚合作用后形成聚多巴胺,该反应活性高,能对各类有机和无机纳米材料进行表面修饰.而且,聚多巴胺表层中的活性基团能与含有氨基和巯基的生物大分子发生迈克尔加成或席夫碱反应,从而将生物大分子固定在材料表面.
　　本文利用聚多巴胺表面修饰MNPs,对所得聚多巴胺表面修饰的四氧化三铁纳米粒子(PD-MNPs)进行了结构表征.结果表明, PD-MNPs尺寸在14 nm左右.同时,成功将黑曲霉脂肪酶(ANL)固定在PD-MNPs上,结果显示在pH=8、固定化时间为12 h条件下,酶负载量为138 mg/g,酶活回收率达到83.6%,而且固定化酶的pH稳定性及热稳定性、储藏稳定性都优于游离酶.动力学研究表明,固定化酶Km值(63.2 mmol/L)低于游离酶(74.5 mmol/L),固定化酶的底物亲和性增强.进一步研究了固定化酶和游离酶在乙腈、二甲基亚砜、乙醇和[HMIm]BF4这四种溶剂中的溶剂耐受性,结果显示固定化酶的耐受性均强于游离酶.采用红外光谱对游离酶和固定化酶二级结构的分析表明,游离黑曲霉脂肪酶经固定化后,α-螺旋和β-折叠含量分别增加了0.84%和2.74%,使得固定化后α-螺旋和β-折叠中存在的氢键能够更好地保持酶结构刚性,避免因结构改变而引起酶失活,增强了固定化酶在溶剂中的耐受性.
　　二氢杨梅素是一种具有类黄酮结构的天然产物,具有抗氧化、抗菌、抗肿瘤和保护肝脏等作用,但其脂溶性很差,很难透过细胞膜被人体吸收.本课题组曾首次以乙酸乙烯酯为酰基供体,采用游离脂肪酶生物催化方法成功将二氢杨梅素酰化.本文考察了PD-MNPs固定化脂肪酶在二氢杨梅素酰化反应中的应用.结果表明,与游离酶相比,固定化酶在反应介质二甲基亚砜中的耐受性更强,反应48 h后其催化二氢杨梅素酰化的转化率接近80%,明显好于游离酶(69%).固定化酶催化二氢杨梅素酰化的最适底物摩尔比、温度和酶量分别为10：1(乙酸乙烯酯：二氢杨梅素)、45oC,和40 U.此外,固定化酶在外界磁场作用下能迅速从反应混合物中分离,从而可回收利用,在重复使用10次后,其活性仍保持在初始活性的55%以上,具有良好的工业应用前景.     

几种金属与二氢杨梅素络合作用的光谱研究

金属离子(M)容易接受配体,成为中心离子,二氢杨梅素(DMY)是藤茶中活性最强的天然活性物质,可作为多基配体与金属发生络合反应.本文研究了DMY-M系统的紫外光谱、荧光光谱及红外光谱,与DMY相比,DMY-M有以下特点:紫外光谱吸收峰、荧光光谱发射峰位置基本不变,但强度减弱;羰基红外吸收峰发生红移,并在500- 700...