Jae-Chun Ryu

Survey of natural occurrence of trichothecene mycotoxins and zearalenone in Korean cereals harvested in 1992 using gas chromatography/mass spectrometry.

For the survey of the natural occurrence of trichothecene mycotoxins, produced by species of fungi imperfecti such as Fusarium and Trichothecium, a sensitive analytical method was developed for the simultaneous detection and quantitation of the major trichothecene mycotoxins, viz. T-2 toxin (T-2), HT-2 toxin (HT-2), nivalenol (NIV), fusarenon-X (F-X), deoxynivalenol (DON), 3-acetyl deoxynivalenol (3-Ac DON), and zearalenone (ZEN), using gas chromatography/mass spectrometry-selected ion monitoring (GC/MS-SIM) mode after trimethyl silyl derivatization. The incidence of NIV and DON in 30 barley samples were 93% and 67%, respectively; the average contents of NIV and DON in positive samples were 390 ng/g (range 40-2038) and 106 ng/g (range 5-361) respectively. In 15 maize samples, the incidences of NIV and DON were 53% and 93% respectively and the average contents were 168 ng/g and 145 ng/g, respectively. These results suggest that NIV and DON were the major contaminating trichothecene mycotoxins in Korean barley and maize samples harvested in 1992.

Pharmacokinetics of propentofylline and the quantitation of its metabolite hydroxypropentofylline in human volunteers

Propentofylline (PPF, 3-methyl-1-(5-oxohexyl)-7-propylxanthine) has been reported to be effective for the treatment of both vascular dementia and dementia of the Alzheimer type. The pharmacological effects of PPF may be exerted via the stimulation of nerve growth factor, increased cerebral blood flow, and inhibition of adenosine uptake. The objectives of this experiment are to determine the kinetic behavior of PPF, to identify, and to quantify its metabolite in human. Blood samples were obtained from human volunteers following oral administration of 200 mg of PPF tablets. For the identification and quantification of the metabolite, 3-methyl-1-(5-hydroxyhexyl)-7-propylxanthine (PPFOH), PPFOH was synthesized and identified by gas chromatography/mass spectroscopy (GC/MS) and1H-nuclear magnetic resonance spectroscopy. The molecular weight of synthesized metabolite is 308 dalton. The PPF and PPFOH in plasma were extracted with diethyl ether and identified by electron impact GC/MS. The plasma concentrations of PPF and PPFOH were determined by gas chromatography/nitrogen phosphorus detector in plasma and their pharmacokinetic parameters were determined. The mean half-life of PPF was 0.74 hr. The areas under the curve (AUCs) of PPF and PPFOH were 508 and 460 ng.hr/ml, respectively. Cmax of PPF was about 828.4 ng/ml and the peak concentration was achieved at about 2.2 hr (Tmax). These results indicate that PPF is rapidly disappeared from blood due to extensive metabolism into PPFOH.

Evaluation of the genetic toxicity of synthetic chemicals (II), a pyrethroid insecticide, fenpropathrin

The detection of many synthetic chemicals used in industry that may pose a genetic hazard in our environment is subject of great concern at present. In this respect, the genetic toxicity of fenpropathrin ((RS)-α-cyano-3-phenoxybenzyl-2,2,3,3-tetramethyl cyclopropane carboxylate, CAS No.: 39515-41-8), a pyrethroid insecticide, was evaluated in bacterial gene mutation system, chromosome aberration in mammalian cell system andin vivo micronucleus assay with rodents. In bacterial gene mutation assay, no mutagenicity of fenpropathrin (62–5000 μg/plate) was observed inSalmonella typhimurium TA 98, 100, 1535 and 1537 both in the absence and in the presence of S-9 metabolic activation system. In mammalian cell system using chinese hamster lung fibroblast, no clastogenicity of fenpropathrin was also observed both in the absence andin the presence of metabolic activation system in the concentration range of 7–28 μg/ml. And also,in vivo micronucleus assay using mouse bone marrow cells, fenpropathrin also revealed no mutagenic potential in the dose range of 27–105 mg/kg body weight of fenpropathrin (i.p.). Consequently, no mutagenic potential of fenpropathrin was observedin vitro bacterial, mammalian mutagenicity systems andin vivo micronucleus assay in the dose ranges used in this experiment.

Genotoxicity study of bojungchisup-tang, an oriental herbal decoction-in vitro chromosome aberration assay in Chinese hamster lung cells andin vivo supravital-staining micronucleus assay with mouse peripheral reticulocytes

The toxicity evaluation of oriental herbal drugs is of great concern at present. Bojungchisuptang (BCST, in Korean), a decocted medicine of oriental herbal mixture, is now well used in clinic at oriental hospitals for the treatment of edema of several diseases in practice. However, the toxicity of the oriental herbal decocted medicines such as genetic toxicity is not well defined until now. In this respect, to clarify the genetic toxicity of BCST,in vitro chromosome aberration assay with Chinese hamster lung (CHL) fibroblasts andin vivo supravital micronucleus assay with mouse peripheral reticulocytes were performed in this study. In the chromosome aberration assay, we used 5,000 μg/ml BCST as maximum concentration because no remarkable cytotoxicity in CHL cells was observed both in the presence and absence of S-9 metabolic activation system. No statistical significant differences of chromosome aberrations were observed in CHL cells treated with 5,000, 2,500 and 1,250 μg/ml BCST for 6 hour both in the presence and absence of S-9 metabolic activation. However, very weak positive result (6.5∼8.0% aberration) of BCST was obtained in the absence of S-9 metabolic activation system at 5,000 μg/ml BCST when treated for 24 hour, i.e. 1.5 normal cell cycle time. And also,in vivo clastogenicity of BCST was studied by acridine orange-supravital staining micronucleus assay using mouse peripheral reticulocytes. We used 2,000 mg/kg as the highest oral dose in this micronucleus assay because no acute oral toxicity of BCST was observed in mice. The optimum induction time of micronucleated reticulocytes (MNRETs) was determined as 36 hours after oral administration of 2,000 mg/kg BCST. No significant differences of MNRETs between control and BCST treatment groups were observedin vivo micronucleus assay. From these results, BCST revealed very weak positive result in chromosome aberration assayin vitro with CHL cells and no clastogenicity in micronucleus assayin vivo.

Identification of Higenamine and its Metabolites in Rat by Gas Chromatography/Mass Spectrometry

Abstract(±)-Higenamine is known as a cardiotonic principle of aconite root (root ofAconitum spp., Ranunculaceae). A simple and sensitive detection method for higenamine was developed by using gas chromatography-mass spectrometry (GC/MS). The recovery of higenamine after extraction and concentration with XAD-2 resin column was around 95% from rat biological fluids such as bile, plasma and urine. The limits of detection of higenamine in these biological fluids were approximately 0.1 ng/ml each. It has well been suggested that tetrahydroisoquinolines possessing catechol moiety such as higenamine should be subjected to the catechol-O-methyl transferase (COMT) activityin vivo. We detected two major peaks of presumed metabolites of higenamine in the total ion chromatogram obtained from the rat urine sample after the oral administration of (±)-higenamine. The scan mass spectrum of one of the metabolites coincided with those obtained from coclaurine (C6-O-methyl higenamine) and those of the other metabolite are suggestive of isococlaurine (C7-O-methyl higenamine).

Metabolism and pharmacokinetics of S-(N,N-diethyldithiocarbamoyl)-N-acetyl-L-cysteine in rats

The metabolism and pharmacokinetics of a mixed disulfide S-(N,N-diethyldithiocarbamoyl)-N-acetyl-L-cysteine (AC-DDTC) were studied in rats. Two metabolites of AC-DDTC following iv and po administration were identified in plasma and liver by HPLC and GC, namely N,N-diethyldithiocarbamate (DDTC) and the methyl ester of DDTC (Me-DDTC). AC-DDTC was very unstablein vivo and could not be detected neither in plasma nor in urine. Pharmacokinetic parameters of DDTC following intravenous administration of AC-DDTC (20 mg/kg) were calculated. DDTC has a low affinity to rat tissue and the total body clearance was 9.0±3.4 ml/min/kg. The mean residence time (MRT) was 111.5±16.3 min. After oral administration of 20 mg/kg AC-DDTC, maximal plasma concentration (Cmax) was 3.8±0.2 nmol/ml and the bioavailability was 7.04%. Cmax for DDTC at a dose of 120 mg/kg. AC-DDTC was 40.1±2.2 nmol/ml. MRT was 47.1±2.8 min at a dose of 20 mg/kg and 110.5±6.0 min at 120 mg/kg.