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N Knebel

Publications and source records attributed to N Knebel.

8 recordsLinked to original sources
PubMed1991

[Antitumor platinum(II) complexes with substituted 2-aminomethylpyridine ligands].

Reaction of K2PtCl4 with the substituted 2-aminomethylpyridines 9, 14, and 22 affords the corresponding dichloroplatinum(II) complexes 3-5. Compounds 3 and 22 show remarkable relative binding affinities for the estrogen receptor. Towards the hormone-independent P388-tumor of the CD2F1-mouse the platinum(II) complexes 4 and 5 are weakly active, complex 3 is inactive. Towards the hormone-independent MDA-MB 231-cell line, compounds 3-5, 9, 14, and 22 exhibit no significant antitumor activity. Towards the hormone-dependent MCF-7 cell line, compounds 3-5, 9, 14 show weak antitumor activity, whereas compound 22 exhibits strong inhibition.

Animals↗
PubMed1990

1-(aminoalkyl)-2-phenylindoles as novel pure estrogen antagonists.

A number of 1-(omega-aminoalkyl)-5-hydroxy-2-(4-hydroxyphenyl)indoles were synthesized and studied for their binding affinities for the calf uterine estrogen receptor and estrogen antagonistic activities. Highest binding affinities were found with derivatives bearing a methyl group in position 3 and a hexamethylene chain between the indole and amino nitrogen atoms. Values for relative binding affinity (RBA) are between 20 and 30 for derivatives 5b, 5c, 5f, and 5h (17 beta-estradiol = 100). In the mouse uterine weight test, no significant agonistic (estrogenic) activity was observed up to a daily dose of 125 micrograms/animal, except for derivatives 5c, 5j, and 5l. 2-Phenylindoles with amino (5b), pyrrolidino (5f), piperidino (5h), and morpholino (5k) groups as the amino function completely suppressed estrone-stimulated uterine growth as a dose of 125 micrograms/animal (100% antagonism). Therefore, these derivatives can be considered as first examples of nonsteroidal pure antiestrogens.

Amines↗
PubMed1989

Carrier mediated action of platinum complexes on estrogen receptor positive tumors.

Three 1,2-diaminoethane-dichloro-platinum(II) complexes linked to 5-hydroxy-2-(4-hydroxyphenyl)-3-methylindole by spacer groups of varying length were evaluated for cytostatic activity in estrogen receptor (ER) positive and negative tumor cells. In vitro, only the growth of ER positive MCF-7 mammary tumor cells was inhibited whereas hormone independent MDA-MB 231 cells did not respond. In vivo, a strong inhibitory effect was only observed in ER positive MXT mammary tumors of the mouse. The complex with a hexyl group as spacer reduced the tumor weight by 89% after 6 weeks of treatment. The R 3327 Dunning prostatic tumor of the rat, which also contains ER was inhibited, too. Generally, the effect in ER negative tumors was weak. These findings can be rationalized by the high binding affinities of the complexes for ER. By the mouse uterine weight test it was shown that the endocrine activity of the complexes is very low. Therefore, a mode of action different from that exerted by estrogens or antiestrogens has to be assumed.

Animals↗
PubMed1989

Platinum complexes with a selective action on estrogen receptor-positive mammary tumors.

Four (1,3-diaminopropane)dichloroplatinum(II) complexes, linked to 5-hydroxy-2-(4-hydroxyphenyl)-3-methylindole by spacer groups of varying lengths, were synthesized and studied for their binding affinities for the calf uterine estrogen receptor. The RBA-values ranged from 1.0 to 4.4 (estradiol: RBA = 100). The endocrine activities of the complexes and their ligands, determined in the mouse uterine weight test, are low. All compounds entered comparative tests using estrogen receptor-positive and negative mammary tumors models. The receptor levels in these tumors were determined by a modified h.p.l.c. micro assay. In cell culture, a growth inhibiting effect was only observed in hormone-sensitive MCF-7 cells, but not in hormone-independent MDA-MB-231 cells. At 10(-6) molar, the cell number was generally decreased by 50%. In vivo, the growth of estrogen receptor-positive MXT mouse tumors was strongly inhibited whereas the hormone-independent MXT mammary tumors showed only a minor response. The most active compound was the platinum complex with a xylidene spacer group (4d-PtCl2) showing a reduction of tumor weight of 84% after 6 weeks of treatment (3 x 20 mg/kg/week). One of the complexes (4c-PtCl2) and its ligand were tested for activity against the hormone sensitive DMBA-induced rat mammary carcinoma. The inhibitory effect of the complex was close to that of cisplatinum. In these experiments, no sign of toxicity was observed. The selective effect on estrogen receptor-positive tumors make an endocrine mode of action both for the complexes and their ligands likely.

Animals↗
PubMed1988

Platinum complexes with binding affinity for the estrogen receptor.

A number of (1,2-diaminoethane)dichloroplatinum(II) complexes, linked to dihydroxy-2-phenylindole by spacer groups of varying lengths, were synthesized and studied for their binding affinities for the calf uterine estrogen receptor. Best binding conditions were provided by the n-hexyl and the p-xylene group as spacer with RBA values of 6.5 (16c) and 4.4 (17c), respectively (17 beta-estradiol: RBA = 100). These values are only slightly lower than those of the corresponding diaminoethane ligands.

Animals↗
PubMedDate not supplied

Reactive intermediates in the oxidation of menthofuran by cytochromes P-450.

Menthofuran, a naturally occurring hepatotoxin, is metabolically activated to chemically reactive intermediates that are capable of covalent binding to cellular proteins. Studies in vivo and in vitro with inhibitors and inducers of hepatic cytochromes P-450 demonstrated an association between hepatocellular damage caused by menthofuran and its metabolic activation and covalent binding to target organ proteins. The same gamma-ketoenal formed from the metabolic precursor of menthofuran, pulegone, is the major electrophilic metabolite of menthofuran as well. Diastereomeric mintlactones also are formed, and studies with H218O and 18O2 indicate that the gamma-ketoenal is a precursor to the mintlactones, as well as other reactive intermediates in the cytochrome P-450 mediated oxidation of menthofuran.

Acetaminophen↗
PubMedDate not supplied

Investigations of mechanisms of reactive metabolite formation from (R)-(+)-pulegone.

1. (R)-(+)-Pulegone is a monoterpene that is oxidized by cytochromes P-450 to reactive metabolites that initiate events in the pathogenesis of hepatotoxicity in mice, rats and humans. 2. Selective labelling of (R)-(+)-pulegone with deuterium revealed that menthofuran was a proximate hepatotoxic metabolite formed by oxidation of the allylic methyl groups of pulegone. Incubations of pulegone with mouse liver microsomes in an atmosphere of 18O2 resulted in the formation of menthofuran that contained only oxygen-18 in the furan moiety. These results are consistent with oxidation of pulegone to an allylic alcohol that reacts intramolecularly with the ketone moiety to form a hemiketal that subsequently dehydrates to generate menthofuran. 3. Studies on the metabolism of menthofuran revealed that it is oxidized by cytochromes P-450 to an electrophilic gamma-ketoenal that reacts with nucleophilic groups on proteins to form covalent adducts. In addition, diastereomeric mintlactones are formed. Investigations with H2(18)O and 18O2 are indicative of a furan epoxide intermediate, or a precursor, in the formation of the gamma-ketoenal and mintlactones.

Animals↗