Integrated HPLC-MS and 1H-NMR spectroscopic studies on acyl migration reaction kinetics of model drug ester glucuronides

1. Acyl glucuronides (AGs) are common, chemically reactive metabolites of acidic xenobiotics. Concerns about the potential of this class of conjugate to cause toxicity in man require efficient methods for the determination of reactivity, and this is commonly done by measuring transacylation kinetics.

2. High-performance liquid chromatography-mass spectrometry (HPLC-MS) and nuclear magnetic resonance (NMR) spectroscopy were applied to the kinetic analysis of AG isomerization and hydrolysis for the 1-β-O-AGs of ibufenac, (R)- and (S)-ibuprofen, and an α,α-dimethylated ibuprofen analogue.

3. Each AG was incubated in either aqueous buffer at pH 7.4 or human plasma at 37°C. Aliquots of these samples, taken throughout the reaction time course, were analysed by HPLC-MS and ¹H-NMR spectroscopy and the results compared.

4. For identification of the AGs incubated in pH 7.4 buffer and for analysis of kinetic rates, ¹H-NMR spectroscopy generally gave the most complete set of data, but for human plasma the use of ¹H-NMR spectroscopy was impractical and HPLC-MS was more suitable. HPLC-MS was more sensitive than ¹H-NMR spectroscopy, but the lack of suitable stable-isotope labelled internal standards, together with differences in response between glucuronides and aglycones, made quantification problematic. Using HPLC-MS a specific 1-β-O-AG-related ion at m/z 193 (the glucuronate fragment) was noted enabling selective determination of these isomers.

5. In buffer, transacylation reactions predominated, with relatively little hydrolysis to the free aglycone observed. In human plasma incubations the observed rates of reaction were much faster than for buffer, and hydrolysis to the free aglycone was the major route. These results illustrate the strengths and weaknesses of each analytical approach for this class of analyte.

     

Solution Stability of Poloxamer 188 Under Stress Conditions

Poloxamer 188 (P188) is a triblock copolymer of the form polyethylene oxide–polypropylene oxide–polyethylene oxide (PEO–PPO–PEO). The center PPO block is hydrophobic, and the side PEO blocks are hydrophilic, resulting in surface-active properties. P188 has been used in the pharmaceutical industry as an excipient in various formulations and drug delivery systems. Although the chemical stability of P188 in the solid state has been reported, there are very few reports detailing the solution state stability. In this study, we report the solution state stability of P188 conducted to evaluate the effects of P188 concentration, temperature, pH and buffer type, and trace metals on chemical stability. The degradation chemistry of P188 and identification of degradation products was studied using various analytical techniques (ultraviolet, gas chromatography–mass spectrometry, and liquid chromatography-mass spectrometry). The degradation of P188 in solution was found to be strongly dependent on temperature, P188 concentration, and buffer type. For the first time, we report that in histidine buffer, oxidation of both P188 and histidine may occur at pharmaceutically relevant conditions. We observed degradation of both histidine and P188 as well as species formed from the mutual interactions of the degradation products from the 2 types of molecules.     

Forced Oxidative Degradation Pathways of the Imidazole Moiety of Daclatasvir

Daclatasvir hydrochloride (DCV) is the active pharmaceutical ingredient of Daklinza, a marketed product for the treatment of hepatitis C viral infection. The intrinsic stability of daclatasvir was evaluated via a forced degradation study. DCV was found to be stable in the solid state. In solution, its carbamate moiety is susceptible to basic hydrolysis, whereas its imidazole is liable to base-mediated autoxidation to form degradants 1 and 3, 7-8, respectively. The imidazole moiety can also be oxidized to form degradants 6-7 in the presence of hydrogen peroxide or azobisisobutyronitrile. The chloro-adduct degradant 9 was also observed in hydrogen peroxide solution. Furthermore, the imidazole moiety is sensitive to photodegradation in solution. Degradants 2-8 were observed in a solution of DCV exposed to high intensity light/UV light; the formation of degradants 2 and 5-8 was postulated through 4 degradation pathways. The degradants 3 and 4 were deemed to be secondary degradants of 7 and 5, respectively.     

木蹄层孔菌石油醚组分的成分分析及抗肿瘤活性研究

目的:分析木蹄层孔菌(Fomes fomentarius)石油醚组分中甾醇和三萜类等成分及其主要抗肿瘤活性物质。方法:采用95%乙醇回流提取法及拌硅胶淋洗方法得到木蹄层孔菌的石油醚组分。用气相色谱-质谱联用技术对石油醚组分甾体和三萜类成分进行分析和鉴定并计算出其含量。用硅胶柱色谱法分离纯化含量最高的7,22-二烯麦角甾-3-酮。采用Alamar Blue法进行体外抗肿瘤活性检测。结果:从木蹄层孔菌石油醚组分中检测出37个成分,鉴定了其中的35个成分,包括10种甾体和三萜类成分。其主要成分为:7,22-二烯麦角甾-3-酮(37.67%)和5,24(28)-二烯麦角甾-3-醇(27.01%)。石油醚组分对细胞株NCI-H460的IC50为75μg.mL-1,7,22-二烯麦角甾-3-酮对细胞株NCI-H460的IC50为30μg.mL-1,抗肿瘤活性与单体浓度存在明显的量效关系。结论:木蹄层孔菌石油醚组分主要成分为7,22-二烯麦角甾-3-酮和5,24(28)-二烯麦角甾-3-醇,抗肿瘤活性物质最高的为7,22-二烯麦角甾-3-酮。研究结果为木蹄层孔菌的进一步开发提供了依据。     

Silicone Oil-Free Polymer Syringes for the Storage of Therapeutic Proteins

Prefilled syringes are a popular choice for the delivery of biopharmaceuticals. However, glass syringes might not be the optimal primary packaging material for all biopharmaceuticals. There is evidence that the necessary lubricant silicone oil in glass syringes can interact with proteins and can be shed from the surface into the product solution. In recent years, silicone oil-free polymer syringes were developed. Despite several advantages, however, a major shortcoming of these polymer systems is their relatively high gas permeability, which might be a limitation for the storage of oxygen sensitive biopharmaceuticals. So far, no long-term protein stability studies regarding such polymer systems have been published. In this study, 2 therapeutic proteins were stored in glass syringes and in silicone oil-free polymer syringes. In addition, polymer syringes stored in nitrogen-filled aluminum pouches or covered with oxygen-tight labels were included. Similar chemical protein stability was achieved at 4°C for all syringes. However, in contrast to the polymer syringes, high particle counts were observed in the glass syringes. Polymer syringes stored in nitrogen-filled aluminum pouches presented a promising alternative for the storage of biopharmaceuticals as they do not expose patients to silicone oil and silicone oil-protein aggregates.     

An assessment of polydispersed species in unfractionated and low molecular weight heparins by diffusion ordered nuclear magnetic resonance spectroscopy method

The primary goal of this project is to extend a ¹H NMR based method, which combines elements of separation on the basis of molecular size with the information specific to ¹H-1D NMR, to the assessment of the heparin contaminant oversulfated chondroitin sulfate (OSCS) and process related impurity dermatan sulfate (DS), and their polydisperse degradation products in samples of unfractionated heparins (UFHs) and low molecular weight heparins (LMWHs) used as the active pharmaceutical ingredients (APIs) in finished pharmaceutical products. The method has been briefly introduced by us in a recent contribution (vide infra). We propose a labelling of the N-acetyl peaks in the ¹H NMR spectra of the UFHs and LMWHs with the parameter D_i, the translational diffusion coefficient available from DOSY NMR. It is shown how DOSY can be applied for screening lots of unfractionated and depolymerised heparins for obtaining molecular size information for heparins and any impurities when using ¹H NMR. The evidence has been presented that title method can be applied as a routine means for assessment of the OSCS and DS contaminants and the polydisperse chemical entities present in the UFHs and LMWHs used as the APIs in heparin pharmaceuticals.