Sanggil Choe

Rhododendric acid A, a new ursane-type PTP1B inhibitor from the endangered plant Rhododendron brachycarpum G. Don

In spite of the critical role of the natural products in drug discovery, surprising little attention has been placed on endangered and rare plant species that could play a pivotal role in pharmaceutical and fiber development. Protein tyrosine phosphatase-1B (PTP1B), which blocks insulin signaling, has been gaining interest to be a promising therapeutic target for the treatment of type 2 diabetes mellitus. Bioassay-guided fractionation on the leaves of Rhododendron brachycarpum G. Don (Ericaceae) yielded seven PTP1B inhibitory triterpenoids, including a new triterpene, rhododendric acid A (1). Their PTP1B inhibitory potency and their lipophilicity were investigated to provide a feasible scaffold that may overcome the innate limitation of the previously reported PTP1B inhibitors.

Antioxidative oligostilbenes from Caragana sinica

Two new oligostilbenes, caragasinins A (5) and B (10), and eight known compounds, kobophenol A (1), (+)-α-viniferin (2), (+)-ampelopsin F (3), pallidol (4), (+)-isoampelopsin F (6), miyabenol C (7), carasinaurone (8) and caraphenol B (9) were isolated from the ethylacetate-soluble extract of the roots of Caragana sinica. The structures of the isolates were determined on the basis of extensive spectroscopic analysis including 1D, 2D NMR and HRESI-MS. These compounds were assessed for antioxidant activities. Caragasinin A (5), caraphenol B (9), and caragasinin B (10) showed moderate DPPH scavenging activity and lipid peroxidation inhibitory activities with IC(50) values ranging from 34.7±1.0 to 89.1±2.3μM.

Identification of N-ethyl-α-ethylphenethylamine in crystalline powder seized for suspected drug trafficking: a research chemical or a new designer drug?

A crystalline powder was found in an unclaimed lost article shipped from Vietnam to South Korea, and it was seized by narcotics agents as an item of suspicious trade. The chemical was suspected to be methamphetamine crystals, and was sent to the National Forensic Service for forensic identification. Elucidation of the chemical structure was carried out using gas chromatography–electron impact ionization–mass spectrometry, liquid chromatography–time-of-flight–mass spectrometry, and 1D and 2D nuclear magnetic resonance spectroscopy. The compound was identified as N-ethyl-α-ethylphenethylamine. Although the narcotic effect of this compound remains unverified, it may be classified as a phenethylamine-based designer drug on the basis of its structure. It appeared that the recipient of this article sought to abuse this chemical in the same way as amphetamines. There is a possibility that this chemical will be widely abused for recreational use in the near future.

Species identification of Papaver by metabolite profiling.

Papaver somniferum L. and Papaver setigerum D.C. are controlled as opium poppy in Korea because they contain narcotic substances such as morphine and codeine. It is one of the critical issues whether the plants similar to opium poppy in shape are controlled plants or not. There are more than 110 species in the genus Papaver worldwide and about 10 species in Korea. As the morphological features of some species are very similar and the alkaloid contents and the ratios among the major alkaloids vary even within the same species, it is often difficult to identify the exact species by the morphological features and/or major alkaloids analysis. To develop a new method that uses metabolite profiling for species discrimination between P. somniferum, Papaver rhoeas and P. setigerum, the gas chromatography/mass spectrometry (GC-MS) data of the alkaline extract were processed with in-house Microsoft Visual Basic(®) modules and the chemical information was analyzed through multivariate statistical analyses such as Hierarchical cluster analysis (HCA), principal component analysis (PCA) and discriminant analysis (DA). The GC-MS results combined with multivariate analysis demonstrated that the metabolite profiling was an efficient technique for the classification and this method will provide a powerful tool for the identification of Korean Papaver species.

Preparation and application of a fortified hair reference material for the determination of methamphetamine and amphetamine.

Quality assurance is one of the major issues in forensic analytical laboratories, where the need for a reference material (RM) has rapidly increased. RMs are very useful for method development and validation, internal quality control or proficiency tests. In the present study, we prepared a RM using drug-free hair for the determination of methamphetamine (MA) and its main metabolite, amphetamine (AP) according to the recommendations of ISO Guide 35. The concentrations of MA and AP were determined using two extraction methods, agitation with 1% HCl in methanol at 38 degrees C and ultrasonication with methanol/5M HCl (20:1), followed by gas chromatography/mass spectrometry (GC/MS) after derivatization with trifluoroacetic anhydride (TFAA). The assignment of values was conducted through the homogeneity study and characterization of the material. Furthermore, an internal proficiency test was performed with the prepared RM, of which the results were compared with those of the authentic hair RM prepared in our previous study. As a result, a hair RM containing MA and AP was prepared at the level of 4.86+/-0.69 ng/mg and 4.63+/-0.44 ng/mg, respectively. Most participants showed satisfactory performances in the internal proficiency test with the both RMs. The hair RM prepared in this study demonstrated its suitability for quality assurance in forensic laboratories.

Advanced analytical method of nereistoxin using mixed-mode cationic exchange solid-phase extraction and GC/MS

Nereistoxin(NTX) was originated from a marine annelid worm Lumbriconereis heteropoda and its analogue pesticides including cartap, bensultap, thiocyclam and thiobensultap have been commonly used in agriculture, because of their low toxicity and high insecticidal activity. However, NTX has been reported about its inhibitory neuro toxicity in human and animal body, by blocking nicotinic acetylcholine receptor and it cause significant neuromuscular toxicity, resulting in respiratory failure. We developed a new method to determine NTX in biological fluid. The method involves mixed-mode cationic exchange based solid phase extraction and gas chromatography/mass spectrometry for final identification and quantitative analysis. The limit of detection and recovery were substantially better than those of other methods using liquid-liquid extraction or headspace solid phase microextraction. The good recoveries (97±14%) in blood samples were obtained and calibration curves over the range 0.05-20 mg/L have R2 values greater than 0.99. The developed method was applied to a fatal case of cartap intoxication of 74 years old woman who ingested cartap hydrochloride for suicide. Cartap and NTX were detected from postmortem specimens and the cause of the death was ruled to be nereistoxin intoxication. The concentrations of NTX were 2.58 mg/L, 3.36 mg/L and 1479.7 mg/L in heart, femoral blood and stomach liquid content, respectively. The heart blood/femoral blood ratio of NTX was 0.76.

Analysis of pharmaceutical impurities in the methamphetamine crystals seized for drug trafficking in Korea

Some methamphetamine (MA) crystals contain pharmaceutical impurities. They often come from the co-ingredients of cold drugs used for extracting ephedrine or pseudoephedrine. Though these impurities are not so commonly encountered, they reflect the trends in precursor chemicals and manufacturing sources. As a result of monitoring impurities in the MA crystals seized in Korea during 2006-2011, 10 species of pharmaceutical impurities were identified by gas chromatography-flame ionization detection and gas chromatography-mass spectrometry. They may be co-ingredients of the legal drugs used as a source of ephedrine or pseudoephedrine. In contrast, some of them are presumed to be adulterants added during or after clandestine synthesis. It is interesting that some of these have been identified in the MA crystals seized in other countries in the same year. Species of pharmaceutical impurities in the MA crystals increased particularly in 2010, indicating a change in precursor chemicals and/or manufacturing sources.

Dimeric ent-kaurane diterpenoids from Isodon excisus.

Five new dimeric ent-kauranoids, biexcisusins A-E (1-5), were isolated from the aerial parts of Isodon excisus. The structures and relative configurations of these compounds were determined on the basis of spectroscopic data interpretation. Of these, biexcisusins C-E (3-5) are dimeric ent-kaurane diterpenoids exhibiting an unprecedented linkage through a nine-membered lactone ring between two ent-kaurane subunits. Compounds 1-5 showed no inhibitory effects on the LPS-induced production of nitric oxide in murine macrophage RAW264.7 cells, up to a dose of 50 μM.

Automated toxicological screening reports of modified Agilent MSD Chemstation® combined with Microsoft Visual Basic® application programs

Agilent GC-MS MSD Chemstation offers automated library search report for toxicological screening using total ion chromatogram (TIC) and mass spectroscopy in normal mode. Numerous peaks appear in the chromatogram of biological specimen such as blood or urine and often large migrating peaks obscure small target peaks, in addition, any target peaks of low abundance regularly give wrong library search result or low matching score. As a result, retention time and mass spectrum of all the peaks in the chromatogram have to be checked to see if they are relevant. These repeated actions are very tedious and time-consuming to toxicologists. MSD Chemstation software operates using a number of macro files which give commands and instructions on how to work on and extract data from the chromatogram and spectroscopy. These macro files are developed by the own compiler of the software. All the original macro files can be modified and new macro files can be added to the original software by users. To get more accurate results with more convenient method and to save time for data analysis, we developed new macro files for reports generation and inserted new menus in the Enhanced Data Analysis program. Toxicological screening reports generated by these new macro files are in text mode or graphic mode and these reports can be generated with three different automated subtraction options. Text reports have Brief mode and Full mode and graphic reports have the option with or without mass spectrum mode. Matched mass spectrum and matching score for detected compounds are printed in reports by modified library searching modules. We have also developed an independent application program named DrugMan. This program manages drug groups, lists and parameters that are in use in MSD Chemstation. The incorporation of DrugMan with modified macro modules provides a powerful tool for toxicological screening and save a lot of valuable time on toxicological work.

Determination of propofol glucuronide from hair sample by using mixed mode anion exchange cartridge and liquid chromatography tandem mass spectrometry

The main objective of this study was to develop and validate a simpler and less time consuming analytical method for determination of propofol glucuronide from hair sample, by using mixed mode anion exchange cartridge and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The study uses propofol glucuronide, a major metabolite of propofol, as a marker for propofol abuse. The hair sample was digested in sodium hydroxide solution and loaded in mixed-mode anion cartridge for solid phase extraction. Water and ethyl acetate were used as washing solvents to remove interfering substances from the hair sample. Consequently, 2% formic acid in ethyl acetate was employed to elute propofol glucuronide from the sorbent of mixed-mode anion cartridge, and analyzed by LC-MS/MS. The method validation parameters such as selectivity, specificity, LOD, LLOQ, accuracy, precision, recovery, and matrix effect were also tested. The linearity of calibration curves showed good correlation, with correlation coefficient 0.998. The LOD and LLOQ of the propofol glucuronide were 0.2 pg/mg and 0.5 pg/mg, respectively. The intra and inter-day precision and accuracy were acceptable within 15%. The mean values of recovery and matrix effect were in the range of 91.7-98.7% and 87.5-90.3%, respectively, signifying that the sample preparation, washing and extraction procedure were efficient, and there was low significant hair matrix effect for the extraction of propofol glucuronide from hair sample on the mixed mode anion cartridge. To evaluate the suitability of method, the hair of propofol administered rat was successfully analyzed with this method.