Degradation of [(14)C]carfentrazone-ethyl under aerobic aquatic conditions.

Carfentrazone-ethyl (CF-E) is an aryl triazolinone reduced-risk herbicide for use on corn, wheat, and soybean. As part of the assessment of its metabolic fate, the aerobic aquatic metabolism of [(14)C]CF-E at a concentration of 0.22 microg/g was investigated. Two separate aquatic sediments (silty clay loam and clay loam soils, flooded with water) were used in the study. At each of eight samplings throughout the 30-day study, the distribution of radioactivity between surface water, sediment, and volatile fractions was assessed. At zero time, the majority of the applied radioactivity was contained in the water layer (83-90%), declining to 70-80% after 30 days. This was coupled with an increase in the percent radioactivity in the soil layer from 4-6% at day 0 to 13-19% after 30 days. Nonextractable soil residues and volatile degradation products were formed in negligible amounts. Analysis of the incubation extracts from either aquatic sediment indicated a rapid conversion (<2 days) of the parent CF-E ester to carfentrazone-chloropropionic acid. Over time, increasing amounts of a cascade of acidic degradation products comprising >90% of the applied radioactivity were formed. Identification of these degradation products was initially achieved through chromatographic comparison with reference synthetic standards and subsequently confirmed using LC-MS analysis. A degradation pathway for CF-E under aerobic aquatic conditions is proposed.

Metabolism of 2-acetylaminofluorene by hepatocytes isolated from rainbow trout.

The metabolism of 2-acetyl-[9-14C]aminofluorene (AAF) by hepatocytes isolated from rainbow trout (Oncorhynchus mykiss), Shasta strain, was investigated in order to assess the competing activation and detoxification pathways which may explain the resistance of this species and strain to the initiation of carcinogenesis by this model carcinogenic aromatic amide. Freshly isolated hepatocytes (per milliliter: 1.0 mg dry wt; 1.5 (10(6)) hepatocytes) incubated with 65 microM AAF for 4 hr converted 15.4 nmol AAF to metabolites, including 7.8 nmol of water-soluble compounds. AAF-derived radioactivity extracted from the incubation mixtures, before and after hydrolysis by beta-glucuronidase and arylsulfatase, was analyzed by reversed-phase HPLC. The metabolite profile following incubation of hepatocytes with 6.5 microM AAF for 4 hr included (as percentage of total metabolites); 7-OH-AAF, 5-/8-/9-OH-AAF and 2-aminofluorene (AF) (17, 2.4, and 2.7%, respectively); conjugates of these respective primary metabolites (39, 9, and 4%, respectively). Glucuronides amounted to 49% of the total metabolites. N-OH-AAF and its conjugates always amounted to < 1% of total metabolites. The relative amount of (unconjugated) AF increased considerably (to 26%) following incubation of hepatocytes with 65 microM AAF, with a corresponding decrease in the total amount of glucuronides formed. Following incubation with 65 microM AAF, 1.6% of AAF metabolites was covalently bound to macromolecules, giving a ratio of covalently bound derivatives to detoxification products of 0.028. These data are consistent with the hypothesis that rainbow trout are resistant to AAF-induced hepatocarcinogenesis, in part, because trout liver efficiently detoxifies AAF and forms only relatively small amounts of active intermediates capable of binding to macromolecules, including DNA.

Anticholinergic activity of bornaprine and its metabolites in the isolated rat atrium.

These studies evaluated the antimuscarinic activity of bornaprine hydrochloride, a synthetic anticholinergic drug utilized in the treatment of parkinsonism. Several of its metabolites were also evaluated. Biological activity was assessed by the ability of the compounds to inhibit the negative inotropic response to carbachol in the isolated left atrium of the rat. Bornaprine showed a pA2 value (concentration required to reduce the agonist response by 50%) of 7.27 +/- 0.21. The exo and endo epimers were approximately equipotent in this regard. One metabolite, the 5-hydroxyl, showed similar activity to the parent compound, whereas 2 other hydroxylated metabolites showed much less effect.

In vitro metabolic transformations of vinblastine: oxidations catalyzed by human ceruloplasmin.

The dimeric Vinca alkaloid vinblastine (VLB) undergoes metabolic transformation to three products in a reaction catalyzed by the human serum copper oxidase ceruloplasmin. The enzyme reaction requires chlorpromazine as a shuttle oxidant, and the course of the oxidation reaction appears to be subject to the nature of the shuttle oxidant used. Preparative-scale incubations have resulted in the isolation of three products, which were characterized by chemical and spectral analyses. The metabolites were identified as the ring fission product catharinine, obtained by oxidation of the Iboga ring system; an enamine/ether derivative obtained by oxidation of the Aspidosperma portion of VLB; and a metabolite embodying the same structural changes in both parts of the vinblastine dimeric structure. Catharinine is identical with the product of VLB oxidation obtained by peroxidase oxidation. The other two products are new metabolites and are derivatives of VLB. All of the metabolites are less active than VLB when tested in vitro vs the human T-cell leukemic cell line (CRFF-CEM).

In vitro metabolic transformations of vinblastine: oxidations catalyzed by peroxidase.

Vinblastine is converted to a single major metabolite during in vitro enzymatic oxidations catalyzed by horseradish peroxidase in the presence of hydrogen peroxide. Preparative-scale enzyme incubation permitted the isolation of sufficient amount of the transformation product for complete structural identification and biological evaluation. The metabolite was identified as catharinine (also known as vinamidine) by 1H and 13C NMR and by mass spectrometry. Incubations conducted in H2(18)O-enriched water gave catharinine in which a single atom of 18O was incorporated into the metabolite structure. The labeling experiment provided evidence for an unusual ring-fission pathway by which peroxidase transforms vinblastine to catharinine. Catharinine is 77 times less active than vinblastine when tested in vitro against the human T-cell leukemic cell line (CRFF-CEM).

Microbial transformation studies on arteannuin B.

The microbial transformation of the sesquiterpene lactone arreannuin B [3] using Aspergillus flavipes produced dihydroarteannuin B [4] as the main transformation product. Preparative-scale fermentation of 3 with Beauveria bassiana, on the other hand, has resulted in the production of two metabolites, 3 beta-hydroxyarteannuin B [5] and 13-hydroxy-11-epi-dihydroarteannuin B [6]. The structure of these metabolites, all of which are new compounds, was established using chemical and spectroscopic techniques. The isomeric dihydrocompound, 11-epi-dihydroarteannuin B [7] and an isomer of arteannuin B [8] were also prepared chemically. All compounds were subjected to 2D-nmr experiments and full 1H- and 13C-nmr assignments were made.

Microbial metabolism of bornaprine, 3-(diethylamino)propyl 2-phenylbicyclo[2.2.1]heptane-2-carboxylate.

Metabolism studies of the anticholinergic drug, bornaprine [3-(diethylamino)propyl 2-phenylbicyclo[2.2.1]heptane-2-carboxylate, an epimeric mixture], in rats, dogs, and humans have been conducted previously, but the identities of the metabolites were not established. Using an in vitro microbial system to study the metabolism of bornaprine resulted in the isolation of four metabolites whose structures were rigorously established using spectroscopic techniques, especially 13C NMR. The four metabolites found were hydroxylated at C-5 or C-6 in the bicyclic ring.