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J F Fitzloff

Publications and source records attributed to J F Fitzloff.

13 recordsLinked to original sources
PubMed2002

Evaluation of commercial Ginkgo biloba dietary supplements for the presence of colchicine by high-performance liquid chromatography.

A high-performance liquid chromatographic method with photodiode array detection was developed for the detection of the presence of colchicine in commercial ginkgo products. The method is based on the baseline separation of constituents in ginkgo samples plus reference colchicine. The minimal detectable concentration of colchicine is 1.0 ng on column in the current assay. By analysis of retention time and UV profile of suspect peaks in the sample with those of reference colchicine, none of the nine commercial ginkgo products analyzed contained colchicine.

Chromatography, High Pressure Liquid↗
PubMed2001

High performance liquid chromatographic analysis of St. John's wort with photodiode array detection.

An RP-HPLC method with photodiode array detection was established for the determination of major constituents (rutin, hyperoside, isoquercitrin, quercitrin, quercetin, pseudohypericin, hyperforin and hypericin) in St. John's Wort dietary supplements. The samples were extracted with methanol by means of sonication in low temperature. The extraction was rapid, with two steps of sonication (30 min each) recovering more than 99% of the major constituents in St. John's Wort samples. The major components were separated by RP-18 chromatography column using a 60-min water-acetonitrile-methanol-trifluoroacetic acid gradient. The quantification was performed by using external standards. Sample preparation and stability of methanolic extract of St. John's Wort were extensively explored. It is worth noting that the major constituents in the methanolic extract of St John's Wort, especially hypericin and pseudohypericin, might be retained by some filter cartridges during the filtration. The current method may serve as a valuable tool for the QA/QC of St. John's Wort dietary supplements.

Chromatography, High Pressure Liquid↗
PubMed2001

Determination of 24(R)-pseudoginsenoside F(11) in North American ginseng using high performance liquid chromatography with evaporative light scattering detection.

A gradient liquid chromatographic method with evaporative light scattering detection (ELSD) for the determination of 24(R)-pseudoginsenoside F(11) in North American ginseng is described. Samples are analyzed by means of a reverse-phase column (Waters Spherisorb ODS-2, C(18)) using acetonitrile and water under gradient conditions as the mobile phase over 20 min. The evaporative light scattering detector (ELSD) used, was set at an evaporating temperature of 35 degrees C and nitrogen gas pressure of 3.4 bar. The detection limit (S/N>5) of 24(R)-pseudoginsenoside F(11) is 53 ng on column.

Calibration↗
PubMed2001

Species difference in stereoselective involvement of CYP3A in the mono-N-dealkylation of disopyramide.

1. To determine which CYP isoenzyme is involved in the N-dealkylation of disopyramide (DP) metabolism in human and dog, and to determine the stereoselectivity of DP metabolism with human CYP and dog CYP isoenzymes, the following in vitro metabolism studies of DP were conducted: correlation between human CYP isoenzyme activities and DP metabolism with human liver microsomes; inhibition of DP metabolism in human and dog liver microsomes with chemical inhibitors of CYP isoenzymes; inhibition of DP metabolism in human microsomes with human CYP antibodies; inhibition of DP metabolism in dog liver microsomes with human and dog CYP antibodies; metabolism of DP with human (CYP3A4) and dog (CYP3A12) cDNA-expressed isoenzymes; determination of Km and Vmax of DP enantiomers by using cDNA-expressed CYP3A4 and CYP3A12. 2. In human liver microsomes, the formation of the mono-N-dealkylated disopyramide (MNDP) metabolite was best correlated with CYP3A4 activities. DP metabolism was substantially inhibited by ketoconazole, troleandomycin (TA) and human CYP3A4 antibody. DP was metabolized by cDNA-expressed CYP3A isoenzymes. In dog liver microsomes, DP metabolism was inhibited by ketoconazole, TA and dog anti-CYP3A12. DP was also metabolized by cDNA-expressed CYP3A12. 3. CYP3A4 and CYP3A12 are the principal isoenzymes involved in DP metabolism in human and dog respectively. There was no stereoselectivity in N-dealkylation of DP by human CYP3A4. However, there was notable stereoselectivity in the N-dealkylation by dog CYP3A12.

Amino Acid Sequence↗
PubMed2001

Determination of astragaloside IV in Radix astragali (Astragalus membranaceus var. monghulicus) using high-performance liquid chromatography with evaporative light-scattering detection.

A reverse-phase high-performance liquid chromatographic method is developed for the determination of astragaloside IV, a characteristic constituent in Radix Astragali. Samples are analyzed by means of a reverse-phase column (Zorbax Eclipse XDB C18) using acetonitrile and water under gradient conditions as the mobile phase for 30 min. An evaporative light-scattering detector is used and set at an evaporating temperature of 43 degrees C with a nebulizing gas (compressed air) pressure of 3.4 bar. The detection limit (signal-to-noise ratio > 5) of astragaloside IV is 40 ng on-column.

Astragalus Plant↗
PubMed2001

A validated method for quantitative determination of saponins in notoginseng (Panax notoginseng) using high-performance liquid chromatography with evaporative light-scattering detection.

A gradient high-performance liquid chromatographic (HPLC) method with evaporative light-scattering detection (ELSD) for the determination of major saponins in a Chinese traditional herbal medicine, Panax notoginseng, is described. Samples were analysed by means of a reverse-phase column (Waters Spherisorb ODS-2, C-18) using acetonitrile and water under gradient conditions as the mobile phase over 60 min. The ELSD used was set at an evaporating temperature of 35 degrees C and pressurized air pressure of 3.4 bars. The detection limit (signal/noise > 3) of the saponins was 50 ng. The method was validated by inter- and intra-day assays and recovery tests.

Chromatography, High Pressure Liquid↗
PubMed2000

Use of high-performance liquid chromatography-tandem mass spectrometry to distinguish Panax ginseng C. A. Meyer (Asian ginseng) and Panax quinquefolius L. (North American ginseng).

A liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed to distinguish Asian ginseng (Panax ginseng C. A. Meyer) and North American ginseng (Panax quinquefolius L.). The method is based on the baseline chromatographic separation of ginsenoside Rf and 24(R)-pseudoginsenoside F11, two potential chemical markers present in ginseng root methanolic extracts, and their unambiguous on-line identification using tandem mass spectrometry. Consistent with the literature, 24(R)-pseudoginsenoside F11 was detected in abundance in North American ginseng roots in excess of 0.1% (w/w) of the dried root. In contrast to some reports, 24(R)-pseudoginsenoside F11 was also identified in Asian ginseng roots at trace levels using LC-MS-MS but at less than 0.0001% (w/w). Besides showing identical tandem mass spectra to authentic 24(R)-pseudoginsenoside F11, the corresponding compound in Asian ginseng root coeluted with standard under different HPLC conditions, thus confirming this compound as 24(R)-pseudoginsenoside F11. Another ginsenoside often used to distinguish Asian and North American ginseng, ginsenoside Rf, was found in abundance in Asian ginseng roots at more than 0.021% (w/w). In Asian ginseng roots, the ratio of ginsenoside Rf to 24(R)-pseudoginsenoside F11 exceeded 700:1. The limit of detection of ginsenoside Rf or 24(R)-pseudoginsenoside F11 was 120 pg injected on-column, and the limit of quantification was 240 pg on-column. In summary, LC-MS-MS analysis of ginseng products for the presence and ratio of ginsenoside Rf and 24(R)-pseudoginsenoside F11 may be used for the unambiguous identification of Asian and North American ginsengs.

Asia↗
PubMed1995

Sample multiplexing for greater throughput in HPLC and related methods.

We present a multiplexing scheme that pools samples for greater efficiency in analysis. The method involves arraying the samples in a matrix and then pooling along rows and columns of the array. Sample pools are analyzed instead of individual samples. The content of a given sample is found by the intersection of a row pool with a column pool. Since this simple pooling scheme can lead to ambiguities in assignments when many samples have the same species, we also suggest a supplementary or augmented pooling scheme, involving the use of pools along diagonals across the sample array, to resolve the ambiguities. We demonstrate the pooling scheme, with resolution of some simple ambiguities, using HPLC for the analysis of fluorophore-labeled amino acids.

Amino Acids↗
PubMed1991

Inhibition of cholesterol side-chain cleavage. Part 5. Synthesis of 22-(p-chlorophenyl) cholesterol analogues.

Three 22-(p-chloroaryl) analogues of cholesterol (6a-c) were synthesized and evaluated as potential inhibitors of the adrenal cholesterol side-chain cleavage enzyme, in comparison with the known 20-aryl analogue, 20-(p-chlorophenyl)-5-prenen-3 beta,20-diol (2b). All were potent inhibitors. An oxygen at C-22 (analogues 6a and 6b) enhanced the strong binding to the enzyme. Two compounds (6b and 6c) are potential substrates of the enzyme. Possible pharmaceutical uses for these compounds and their derivatives are discussed.

Adrenal Glands↗
PubMed1990

Lindane.

Explore the source record for details and available documents.

Adult↗
PubMed1984

Epoxidation of the lindane metabolite, beta-PCCH, by human- and rat-liver microsomes.

Human- and rat-liver microsomes convert the lindane metabolite, beta-PCCH (beta-1,3,4,5,6-pentachlorocyclohex-1-ene (3,4,6/5-PCCH] to the metabolites: 1,2,4-TCB (1,2,4-trichlorobenzene), 1,2,3,4-TTCB (1,2,3,4-tetrachlorobenzene), 2,4,5-TCP (2,4,5-trichlorophenol), 3,4,5/6-PCCOL (1,2,4,5,6-pentachlorocyclohex-1-en-3-ol) and beta-PCCH oxide (1,2,3,4,5-pentachloro-7-oxabicyclo[4.1.0]heptane) or (3,4,6/5-PCCH oxide). The identity of the beta-PCCH oxide is confirmed by column chromatography and g.l.c.-mass spectrometry, in comparison to characterized synthetic material. The stability of the beta-PCCH oxide is indicated by its resistance to hydrolysis by microsomal epoxide hydrolase (EC. 3.3.2.3), or various aqueous acid conditions. It shows no mutagenicity using S. typhimurium strain TM677. However, in levels above 0.05 mg/ml it was lethal to the test cells. It is not a substrate for and is only a weak inhibitor of epoxide hydrolase. A stable halogenated hydrocarbon epoxide metabolite is described. Its toxicological role, if any, remains unaccounted for.

Animals↗
PubMed1982

Lindane metabolism by human and rat liver microsomes.

1. Human liver microsomes convert lindane (gamma isomer of 1,2,3,4,5,6-hexachlorocyclohexane) to four major primary metabolites; gamma-1,2,3,4,5,6-hexachlorocyclohex-1-ene (3,6/4,5-HCCH), gamma-1,3,4,5,6-pentachlorocyclohex-1-ene (3,6/4,5-PCCH), beta-1,3,4,5,6-pentachlorocyclohex-1-ene (3,4,6/5-PCCH), and 2,4,6-trichlorophenol (2,4,6-TCP); and two major secondary metabolites; 2,3,4,6-tetrachlorophenol (2,3,4,6-TTCP) and pentachlorobenzene (PCB). 2. Under the same conditions, rat liver microsomes produce 3,6/4,5-HCCH, 2,4,6-TCP and 2,3,4,6-TCCP at rates similar to human liver microsomes. 3,4,6/5-PCCH is produced at much lower rates and 3,6/4,5-PCCH and PCB are not detected when lindane is incubated with rat liver microsomes for up to 30 min. 3. The identity of 3,4,6/5-PCCH, previously not identified as a mammalian metabolite of lindane, is confirmed by column chromatography and g.l.c.-mass spectrometry by comparison with authentic material. 4. It is concluded that there is potentially substantial hepatic metabolism by humans of lindane, a topically used scabicide and pediculicide.

Adult↗