A new diterpenoid alkaloid from Aconitum hemsleyanum

Abstract

A new C₁₉-diterpenoid alkaloid named hemsleyaline (1), along with fourteen known alkaloids (2-15), were isolated from the roots of Aconitum hemsleyanum Pritz. (Ranunculaceae), a herbal medicine in southwest China. Their structures were established on the basis of extensive spectroscopic analyses. Compound 1 showed mild cholinesterase inhibitory effect with IC₅₀ value of 471?±?9?μM.     

Electrogravimetric Analysis by Quartz-Crystal Microbalance on the Consumption of the Neurotransmitter Acetylcholine by Acetylcholinesterase

Electrogravimetric analysis was performed on the consumption of the neurotransmitter Acetylcholine (ACh) by Acetylcholinesterase (AChE) in situ and in real time. Michaelis-Menten assumption was achieved by using an enzyme micro-reactor in which the total enzyme was anchored in a quartz crystal microbalance chip (QCM-chip) with a strategically engineered self-assembled monolayer (SAM) of alkanethiols, which can prevent diffusion-controlled or spatially restricted kinetics. The real-time frequency changes indicated the rate of the products formation from enzymatic reaction. The QCM-chip was tested showing that it could demonstrate AChE inhibition by physostigmine.     

Calorimetric Determination of Phosphorylated Serum Cholinesterase and Its Reactivation by an Antidote

Abstract

Serum cholinesterase, inhibited in vitro up to 92% by 0, 0 dimethyl-2, 2-dichlorovinyl phosphate (4.52 × 10^?9 mole/ml of 40% serum), was reactivated up to 35% with 2-pyridine aldoxime methiodide (3.5 × 10^?6 mole/ml of 40% serum). Evaluation was based on the reaction rate between cholinesterase and acetylcholine chloride (2.2 × 10^?6 mole) measured with a microcalorimeter. It was thus possible to approximate the “normal” or pre-exposure level of serum cholinesterase, while simultaneously determining the extent of poisoning.     

N-Methyl indoxyl Esters as Substrates for Cholinesterase

Abstract

Several esters were prepared as substrates for cholinesterase: the acetate, propionate and butyrate esters of N-methyl indoxyl, umbelliferone acetate, and the acetate and butyrate esters of 4-methyl umbelliferone. Comparison of these substrates with other fluorogenic esters: indoxyl acetate, indoxyl butyrate, resorufin acetate, B-carbonaphthoxycholine, and β-naphthyl acetate indicated that N-methyl indoxyl butyrate was the best substrate for pseudo cholinesterase. Analysis of as little as 5 × 10^?6 units per ml. of cholinesterase can be performed by a direct initial reaction-rate method in 2–3 minutes with an accuracy and precision of about 1.5%.     

A pH-Stat Approach to the Enzymatic Inhibition Analysis of Some Selected Serum Cholinesterase Inhibitors

Abstract

An enzymatic method is described for the pH-stat determination of a series of alkaloids, vitamins, sulfonamides and anions based on the inhibitory effect on the cholinesterase-catalyzed hydrolysis of butyrylcholine iodide (BuCh). All analyses were done at 25.0°C and pH 8.00 Creadable reproducibility of ± 0.02 pH unit)- Sensitivity ranges from 13 ng (physostigmine) to 0.86 g (niacinamide). The precision is < 2.0% with the exception of physostigmine which is ≤ 5.2%. The average recovery and analysis times were (98.1–104.1)% and 10 min., respectively. Complete Inhibition curves are presented and the relative inhibitory “potency” of the compounds examined is inferred.     

血清胆碱酯酶水平在脓毒症患者诊断中的应用价值分析

目的分析脓毒症患者胆碱酯酶含量及其与降钙素原的相关性,为早期诊断脓毒症提供一个新的初筛检测敏感性指标。方法选择60例脓毒症患者为观察组,另选择同期非脓毒症患者60例作为对照组,测定两组患者血清胆碱酯酶活性,且测定观察组PCT含量,分析PCT与胆碱酯酶的相关性。结果观察组胆碱酯酶含量明显高于对照组,差异有统计学意义(P0.05);胆碱酯酶与降钙素原呈现一定线性相关,相关性曲线为:y=2 325.23 x+239 882.3(r=0.843)。结论血清胆碱酯酶结果与降钙素原呈现一定线性关系,可考虑用于早期评估脓毒症及预后情况。     

胆碱酯酶催化反应的量子化学研究——氧化对组氨酸、丝氨酸残基间氢迁移的影响

考虑到氧化对一些酶、核酸、细胞膜的生物活性丧失起着较大的作用,用量子化学半经验 CNDO/2法,从理论上探讨了胆碱酯酶中的组氨酸、丝氨酸残基间的氢键形成、氢迁移过程受氧化影响的大小,给出一些有益的信息。     

Immobilized enzymes as analytical reagents

Immobilized enzymes are becoming increasingly popular as analytical reagents because of their reusability, stability, and sensitivity to many inhibitors that would seriously interfere in assays using soluble enzymes. In this article, some of the kinetic and catalytic effects of immobilized enzymes in analysis will be discussed. The shift of the activity-pH profile curves on immobilization, the changes in temperature dependence. the inhibitor constants (K₁). Michaelis constants (K _m ), and the maximum velocity (V_max). plus others, will be discussed. Finally, the use of these immobilized enzymes in fluorometric and electrochemical monitoring systems will be shown, and the future of these reagents in various areas will be discussed. A survey of enzyme electrodes will be presented as an example of the use of immobilized enzymes. Application of immobilized enzyme technology to the assay of BUN, glucose, uric acid, amino acids, ethanol. and other metabolites will be discussed.     

Spectroscopic Determination of Cholinesterase Activity and Inhibition in Sol-Gel Media

Biological activity of cholinesterases can be determined by optically monitoring the enzymatic reaction with indophenyl acetate, (N-4′-acetoxyphenyl)-4-quinone imine. At pH 8.0 cholinesterases hydrolyze this yellow dye to yield a blue reaction product. Cholinesterase inhibitors reduce the rate of this hydrolysis. Thus, by monitoring absorbance of the hydrolysis product at its maximum (630 nm) as a function of time, reaction rates of both cholinesterase activity and cholinesterase inhibition may be quantified spectroscopically. Using this technique, we measured the enzymatic activity of butyrylcholinesterase (BuChE) molecules encapsulated in tetramethyl orthosilicate (TMOS) silicate gel-glass prepared by hydrolysis and condensation. This activity is reduced, in a concentration-dependent manner, by the reversible cholinesterase inhibitors 1,5-bis(4-allyldimethyl-ammoniumphenyl) pentan 3-one dibromide (BADAPP) and 9-amino-1,2,3,4-tetrahydroacridine (THA; tacrine, Cognex). The gel-glasses are rigid, and compact, transparent and porous enough to allow reagents to diffuse in and out.     

Microalgae as a Potential Functional Ingredient: Evaluation of the Phytochemical Profile,Antioxidant Activity and In-Vitro Enzymatic Inhibitory Effect of Different Species

The functional food market has been in a state of constant expansion due to the increasing awareness of the impact of the diet on human health. In the search for new natural resources that could act as a functional ingredient for the food industry, microalgae represent a promising alternative, considering their high nutritional value and biosynthesis of numerous bioactive compounds with reported biological properties. In the present work, the phytochemical profile, antioxidant activity, and enzymatic inhibitory effect aiming at different metabolic disorders (Alzheimer’s disease, Type 2 diabetes, and obesity) were evaluated for the species Porphyridium purpureum, Chlorella vulgaris, Arthorspira platensis, and Nannochloropsis oculata. All the species presented bioactive diversity and important antioxidant activity, demonstrating the potential to be used as functional ingredients. Particularly, P. purpureum and N. oculata exhibited higher carotenoid and polyphenol content, which was reflected in their superior biological effects. Moreover, the species P. purpureum exhibited remarkable enzymatic inhibition for all the analyses.