HPLC法同时测定化妆品中3-O-乙基抗坏血酸和抗坏血酸棕榈酸酯

建立了同时测定化妆品中3-O-乙基抗坏血酸和抗坏血酸棕榈酸酯的分析方法。样品用甲醇提取剂提取后经反相C_(18)柱(4.6×250 mm,5μm)分离,采用0.05%磷酸-乙腈作为流动相,梯度洗脱,流速为1.0 mL/min,二极管阵列检测器进行检测,检测波长为245 nm和240 nm,外标法定量。在优化的实验条件下,3-O-乙基抗坏血酸在1~100 mg/L线性关系良好,在空白样品中添加10、50、100 mg/kg 3个浓度水平时,得到的回收率为95%~103%,相对标准偏差为3.1%~5.9%。方法的检出限(S/N=3)为3.0 mg/kg,定量限(S/N=10)为10.0mg/kg;抗坏血酸棕榈酸酯在2~200mg/L线性关系良好,在空白样品中添加20、100、200 mg/kg 3个浓度水平时,得到的回收率为98%~104%,相对标准偏差为2.7%~4.6%。方法的检出限(S/N=3)为6.0 mg/kg,定量限(S/N=10)为20.0 mg/kg。     

Process investigation, electrochemical characterization and optimization of LiFePO4/C composite from mechanical activation using sucrose as carbon source

LiFePO₄/C composite was synthesized by mechanical activation using sucrose as carbon source. High-energy ball milling facilitated phase formation during thermal treatment. TG-DSC and TPR experiments demonstrated sucrose was converted to CH_x intermediate before completely decomposed to carbon. Ball milling time, calcination temperature and dwelling time all had significant impact on the discharge capacity and rate performance of the resulted power. The optimal process parameters are high-energy ball milling for 2-4 h followed by thermal treatment at 700 °C for 20 h. The product showed a capacity of 174 mAh/g at 0.1C rate and around 117 mAh/g at 20C rate with the capacity fade less than 10% after 50 cycles. Too low calcination temperature or insufficient calcination time, however, could result in the residual of CH_x in the electrode and led to a decrease of electrode performance.     

Fabrication and characterization of 1D brushite nanomaterials via sucrose ester reverse microemulsion

In the present study, 1-dimensional (1D) brushite nanomaterials were fabricated through sucrose ester based reverse microemulsion for the first time. X-ray diffraction patterns revealed that the nanomaterials possessed brushite crystal phase with trace amount of hydroxyapatite. The size and morphology of brushite crystals were governed by the changes in the aqueous-to-sucrose ester weight ratio at low initial reactant concentration, giving rise to rod-like and fibre-like 1D nanomaterials. Brushite nanorods and nanofibres with average diameters of 25.53 ± 4.60 nm (aspect ratio  6) and 76.18 ± 19.74 nm (aspect ratio  40), respectively, had been synthesized. As the reactant concentration increased, it became the key factor in controlling nucleation and crystal growth, rendering the aqueous-to-sucrose ester ratio unimportant. Formation mechanism of various morphologies of brushite crystals is postulated.     

酒精液滴在蔗糖溶液中汽化冷却传热及其结晶过程

在一汽升式循环管中于减压条件下研究了冷剂酒精在高粘度高浓度的蔗糖水溶液中直接接触汽化传热过程，讨论了冷剂流量，冷剂进口温度和蔗糖溶液的粘度和浓度等操作条件对体积传热量的影响。实验结果表明：冷剂流量Ｖｄ＝０．９￣１．９ｍｌ／ｍｉｎ，冷剂进口温度为４５￣６０℃时，传热效果较好，在此基础上初步探讨了酒精汽化冷却法制取蔗糖晶核的过程，利用显微照相技术分析了晶核的外观特性。     

维生素C棕榈酸酯的合成

对在浓硫酸催化下维生素C和棕榈酸直接酯化合成维生素C棕榈酸酯的工艺进行了改进,主要是在分离过程中选 取了更适宜的萃取剂,并对工艺条件进行优化。该方法操作简单,步骤少且收率高,更适宜工业化生产。产品标准符合美国药典。     

Rheological properties of fermented milk produced by a single exopolysaccharide producing Streptococcus thermophilus strain in the presence of added calcium and sucrose

The effect of calcium supplementation, presence of exopolysaccharides (EPS) and sucrose on the texture of low-fat fermented milk was examined. Reconstituted skim milk (14%) was acidified by 2% glucono-δ-lactone (GDL) or a single strain, EPS-producing Streptococcus thermophilus , and incubated at 42°C. The levels of calcium and sucrose addition ranged from 0 to 9 m m and 0 to 45 m m respectively. Compared with acidified milk (GDL), fermented milk containing EPS showed different rheological properties in the presence of added calcium and sucrose. Calcium addition reduced gel characteristics: G', K, and the second maximum of derivative of shear rate-shear stress; while sucrose addition also increased them but subsequently reduced syneresis. Added calcium or sucrose increased gel hysteresis and reduced apparent yield stress.     

Liraglutide Counteracts Endoplasmic Reticulum Stress in Palmitate-Treated Hypothalamic Neurons without Restoring Mitochondrial Homeostasis

One feature of high-fat diet-induced neurodegeneration in the hypothalamus is an increased level of palmitate, which is associated with endoplasmic reticulum (ER) stress, loss of CoxIV, mitochondrial fragmentation, and decreased abundance of MC4R. To determine whether antidiabetic drugs protect against ER and/or mitochondrial dysfunction by lipid stress, hypothalamic neurons derived from pre-adult mice and neuronal Neuro2A cells were exposed to elevated palmitate. In the hypothalamic neurons, palmitate exposure increased expression of ER resident proteins, including that of SERCA2, indicating ER stress. Liraglutide reverted such altered ER proteostasis, while metformin only normalized SERCA2 expression. In Neuro2A cells liraglutide, but not metformin, also blunted dilation of the ER induced by palmitate treatment, and enhanced abundance and expression of MC4R at the cell surface. Thus, liraglutide counteracts, more effectively than metformin, altered ER proteostasis, morphology, and folding capacity in neurons exposed to fat. In palmitate-treated hypothalamic neurons, mitochondrial fragmentation took place together with loss of CoxIV and decreased mitochondrial membrane potential (MMP). Metformin, but not liraglutide, reverted mitochondrial fragmentation, and both liraglutide and metformin did not protect against either loss of CoxIV abundance or MMP. Thus, ER recovery from lipid stress can take place in hypothalamic neurons in the absence of recovered mitochondrial homeostasis.     

烟叶蔗糖酯研究进展

综述了近些年来国内外有关烟草蔗糖酯的提取、分离与鉴定、生物学活性以及在烟株内的合成路径研究,并提出了未来烟草蔗糖酯研究的重点和方向。     

Influence of processing on the content of sugars in green Arabica coffee beans

Quantitative analyses of low molecular sugars in green coffees (Coffea arabica L. var. Acaià) that were processed in parallel either by the traditional wet or the traditional dry method, revealed a close correlation between the kind of post-harvest treatment and the contents of fructose and glucose. While in washed coffee beans (wet processing) only low amounts of these both hexoses were present, those in unwashed coffees (dry processing) were significantly higher. Model-processing experiments in the laboratory confirmed these findings. Moreover, a comparison with the untreated controls revealed that the low levels of both sugars are the consequence of a decrease in the case of wet processing, whereas they remained unchanged or even increased in the case of dry processing. Further minor sugars are also affected by post-harvest treatment. The amounts of galactose, arabinose and mannose show a similar arrangement as those for glucose and fructose, although their overall concentration is about 100-fold lower. Sucrose, the major low molecular sugar in green coffee beans, is not significantly affected by coffee processing. The influence of an active seed metabolism on the observed alterations of the sugar concentrations is discussed.     

化学与生物法制备抗坏血酸棕榈酸酯及其食品应用研究进展

L-抗坏血酸棕榈酸酯(L-AP),是一种重要的抗坏血酸衍生物,是一种高效,营养,绿色的食品添加剂,它还是目前中国唯一允许在婴儿食品中添加的抗氧化剂。目前L-AP的制备方法主要有化学法与生物法两种,但作为食品添加剂的L-AP必须用生物催化法获得。本文详述了化学与生物法制备L-AP的研究进展,详细介绍了目前生物法主要通过优选酶种类与反应介质、优化反应条件和外加辅助场等手段提高产物得率,并进一步介绍了L-AP在各领域中的实际应用现状。