保健食品中7种烟酰胺类化合物含量测定

目的：构建一种超高效液相色谱—串联质谱法（UPLC-MS/MS）同时测定保健食品中7种烟酰胺类化合物含量的方法。方法：样品用10%甲醇水溶解,通过超声提取,以10 mmol/L乙酸铵—乙腈作为梯度洗脱的流动相,采用电喷雾离子源（ESI）,正负离子模式扫描,多反应监测（MRM）模式对7种烟酰胺类化合物进行监测。结果：7种烟酰胺类化合物在各质量浓度范围内呈良好线性,相关系数均＞0.996,检出限（LOD）为0.075~0.600 mg/kg,回收率为84.6%~108.6%,相对标准偏差为2.1%~8.7%（n=6）。结论：该方法操作简单、快速、高效,回收率高,精密度良好,可用于保健食品中烟酰胺等类似物的定性定量分析。     

粘胶织物中烟酰胺的释放曲线及其模型拟合

为将新兴的绿色、高效的超临界CO₂流体整理技术用于生物活性纺织品开发,提高服用类织物附加值,以生物活性药物烟酰胺为模型药物,粘胶织物为基材,利用超临界CO₂流体分别在不同温度、压力条件下制备负载有烟酰胺的生物活性粘胶织物,将其置于释放介质中,考察烟酰胺从粘胶织物中释放行为的影响因素。结果表明：烟酰胺从粘胶织物中的绝对释放量及绝对释放速率与其在粘胶织物上的负载量正相关;低流体温度(60℃)以及高流体压力(20 MPa)下制备的生物活性粘胶织物累积释放百分比及累积释放速率更低,释放平衡时分别接近87.6%、87.3%;烟酰胺从粘胶织物中的释放行为符合Korsmeyer-Peppas模型,其扩散以菲克扩散为主。     

2-氨基-5-溴烟醛的合成

以烟酰胺为原料,经环合、酸解、溴代反应制得2-氨基-5-溴烟醛(1),并对其制备工艺进行优化和改进,结构经ESI-MS、1H NMR确证。改进后的工艺合成路线较短,操作简单,反应条件较温和,生产成本低,收率为37.4%(以烟酰胺计),具有较好的工业应用前景。     

Application of reduced graphene oxide and carbon nanotube modified electrodes for measuring the enzymatic activity of alcohol dehydrogenase

An electrochemical method was developed to measure the enzymatic activity of alcohol dehydrogenase (ADH) by monitoring the amount of reduced nicotinamide adenine dinucleotide (NADH) generated in the catalysed oxidation of ethanol by ADH. The concentration of NADH was determined by amperometric measurements, which recorded the oxidation current of NADH versus time on reduced graphene oxide and functionalised multi-walled carbon nanotube modified electrodes. The initial reaction rates and the apparent Michaelis constants of the enzymatic reaction were obtained in the absence and presence of Al³⁺ and nanometre-sized tridecameric aluminium polycationic (nano-Al₁₃) species. The results showed that Al³⁺ and nano-Al₁₃ exhibited inhibitory effect on the enzymatic activity of ADH. Fluorescence and circular dichroism spectra indicated the inhibitory effect was likely caused by the conformational changes of ADH and/or NADH induced by Al³⁺ and nano-Al₁₃.     

Virtual Drug Repositioning as a Tool to Identify Natural Small Molecules That Synergize with Lumacaftor in F508del-CFTR Binding and Rescuing

Cystic fibrosis is a hereditary disease mainly caused by the deletion of the Phe 508 (F508del) of the cystic fibrosis transmembrane conductance regulator (CFTR) protein that is thus withheld in the endoplasmic reticulum and rapidly degraded by the ubiquitin/proteasome system. Cystic fibrosis remains a potentially fatal disease, but it has become treatable as a chronic condition due to some CFTR-rescuing drugs that, when used in combination, increase in their therapeutic effect due to a synergic action. Also, dietary supplementation of natural compounds in combination with approved drugs could represent a promising strategy to further alleviate cystic fibrosis symptoms. On these bases, we screened by in silico drug repositioning 846 small synthetic or natural compounds from the AIFA database to evaluate their capacity to interact with the highly druggable lumacaftor binding site of F508del-CFTR. Among the identified hits, nicotinamide (NAM) was predicted to accommodate into the lumacaftor binding region of F508del-CFTR without competing against the drug but rather stabilizing its binding. The effective capacity of NAM to bind F508del-CFTR in a lumacaftor-uncompetitive manner was then validated experimentally by surface plasmon resonance analysis. Finally, the capacity of NAM to synergize with lumacaftor increasing its CFTR-rescuing activity was demonstrated in cell-based assays. This study suggests the possible identification of natural small molecules devoid of side effects and endowed with the capacity to synergize with drugs currently employed for the treatment of cystic fibrosis, which hopefully will increase the therapeutic efficacy with lower doses.     

不同部位猪肉肌纤维类型组成与品质特性比较研究

为比较不同部位猪肉肌纤维类型组成与品质特性的差异,选取9头6月龄杜长大三元杂交猪背最长肌(Longissimus dorsi)、半膜肌(Semimembranosus)和半腱肌(Semitendinosus)3个部位猪肉作为研究对象,通过烟酰胺腺嘌呤二核苷酸四唑氧化还原酶(nicotinamide adenine dinucleotide-tetrazolium reductase,NADH-TR)染色法研究不同部位猪肉的肌纤维类型组成,并分析肌纤维类型数量比例、平均直径、横截面积、密度等肌纤维特性;测定不同部位猪肉的品质特性(p H值、色泽、蒸煮损失率、剪切力以及质构特性)。结果表明,背最长肌和半膜肌中主要为ⅡB型肌纤维(P<0.05),数量比例分别为82.03%和53.22%,半腱肌则主要由Ⅰ型(45.44%)和ⅡB型(39.01%)肌纤维组成。半膜肌中各类型肌纤维的平均直径和横截面积较大,总肌纤维密度最小(P<0.05),为42.15根/mm2。背最长肌的亮度值和蒸煮损失率最高(P<0.05),pH值和红度值最低(P<0.05);半膜肌的剪切力最高(P&l...     

Cellular Redox State Acts as Switch to Determine the Direction of NNT-Catalyzed Reaction in Cystic Fibrosis Cells

The redox states of NAD and NADP are linked to each other in the mitochondria thanks to the enzyme nicotinamide nucleotide transhydrogenase (NNT) which, by utilizing the mitochondrial membrane potential (mΔΨ), catalyzes the transfer of redox potential between these two coenzymes, reducing one at the expense of the oxidation of the other. In order to define NNT reaction direction in CF cells, NNT activity under different redox states of cell has been investigated. Using spectrophotometric and western blotting techniques, the presence, abundance and activity level of NNT were determined. In parallel, the levels of NADPH and NADH as well as of mitochondrial and cellular ROS were also quantified. CF cells showed a 70% increase in protein expression compared to the Wt sample; however, regarding NNT activity, it was surprisingly lower in CF cells than healthy cells (about 30%). The cellular redox state, together with the low mΔΨ, pushes to drive NNT reverse reaction, at the expense of its antioxidant potential, thus consuming NADPH to support NADH production. At the same time, the reduced NNT activity prevents the NADH, produced by the reaction, from causing an explosion of ROS by the damaged respiratory chain, in accordance with the reduced level of mitochondrial ROS in NNT-loss cells. This new information on cellular bioenergetics represents an important building block for further understanding the molecular mechanisms responsible for cellular dysfunction in cystic fibrosis.     

Nicotinamide Effectively Suppresses Fusarium Head Blight in Wheat Plants

Pyridine nucleotides such as a nicotinamide adenine dinucleotide (NAD) are known as plant defense activators. We previously reported that nicotinamide mononucleotide (NMN) enhanced disease resistance against fungal pathogen Fusarium graminearum in barley and Arabidopsis. In this study, we reveal that the pretreatment of nicotinamide (NIM), which does not contain nucleotides, effectively suppresses disease development of Fusarium Head Blight (FHB) in wheat plants. Correspondingly, deoxynivalenol (DON) mycotoxin accumulation was also significantly decreased by NIM pretreatment. A metabolome analysis showed that several antioxidant and antifungal compounds such as trigonelline were significantly accumulated in the NIM-pretreated spikes after inoculation of F. graminearum. In addition, some metabolites involved in the DNA hypomethylation were accumulated in the NIM-pretreated spikes. On the other hand, fungal metabolites DON and ergosterol peroxide were significantly reduced by the NIM pretreatment. Since NIM is relative stable and inexpensive compared with NMN and NAD, it may be more useful for the control of symptoms of FHB and DON accumulation in wheat and other crops.