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Robert Morfin – One of the best experts on this subject based on the ideXlab platform.
Epimerase activity of the human 11beta-hydroxysteroid dehydrogenase type 1 on 7-hydroxylated C19-steroids.The Journal of steroid biochemistry and molecular biology, 2009Co-Authors: Olivier Hennebert, Matthieu Montes, Alain Favre-reguillon, Henry Chermette, Clotilde Ferroud, Robert MorfinAbstract:
Cytochrome P4507B1 7alpha-hydroxylates dehydroepiandrosterone (DHEA), epiandrosterone (EpiA) and 5alpha-androstane-3beta,17beta-diol (Adiol). 11beta-Hydroxysteroid dehydrogenase type 1 (11beta-HSD1) interconverts 7alpha- and 7beta-forms. Whether the interconversion proceeds through oxido-reductive steps or epimerase activity was investigated. Experiments using [(3)H]-labelled 7beta-hydroxy-DHEA, 7beta-hydroxy-EpiA and 7beta-hydroxy-Adiol showed the (3)H-label to accumulate in the 7-oxo-DHEA trap but not in 7-oxo-EpiA or 7-oxo-Adiol traps. Computed models of 7-oxygenated steroids docked in the active site of 11beta-HSD1 either in a flipped or turned form relative to cortisone and cortisol. 7-Oxo-steroid reduction in 7alpha- or 7beta-hydroxylated derivatives resulted from either turned or flipped forms. 11beta-HSD1 incubation in H(2)(18)O medium with each 7-hydroxysteroid did not incorporate (18)O in 7-hydroxylated derivatives of EpiA and Adiol independently of the cofactor used. Thus oxido-reductive steps apply for the interconversion of 7alpha- and 7beta-hydroxy-DHEA through 7-oxo-DHEA. Epimerization may proceed on the 7-hydroxylated derivatives of EpiA and Adiol through a mechanism involving the cofactor and Ser(170). The physiopathological importance of this epimerization process is related to 7beta-hydroxy-EpiA production and its effects in triggering the resolution of inflammation.
Steroid substrate-induced epimerase mechanism in the active site of the human 11&946;-hydroxysteroid dehydrogenase type 1Nature Precedings, 2008Co-Authors: Olivier Hennebert, Matthieu Montes, Alain Favre-reguillon, Henry Chermette, Clotilde Ferroud, Robert MorfinAbstract:
Cytochrome P4507B1 7[alpha]-hydroxylates dehydroepiandrosterone (DHEA), epiandrosterone (EpiA) and 5[alpha]-androstane-3[beta],17[beta]-diol (Adiol). 11[beta]-Hydroxysteroid dehydrogenase type 1 (11[beta]-HSD1) interconverts 7[alpha]- and 7[beta]- forms. Whether the inter-conversion proceeds through oxido-reductive steps or epimerase activity is investigated. Experiments using ^3^H-labeled 7[beta]-hydroxy-DHEA, 7[beta]-hydroxy-EpiA and 7[beta]-hydroxy-Adiol show the ^3^H-label to accumulate in 7-oxo-DHEA trap but neither in 7-oxo-EpiA nor 7-oxo-Adiol traps. Computed models of 7-oxygenated steroids dock in the active site of 11[beta]-HSD1 either in a flipped or turned form relative to cortisone and cortisol. 7-Oxo-steroid reduction in 7[alpha]- or 7[beta]-hydroxylated derivatives results from either turned or flipped forms. 11[beta]-HSD1 incubation in H~2~^18^O medium with each 7-hydroxysteroid did not incorporate ^18^O in 7-hydroxylated derivatives of EpiA and Adiol independently of the cofactor used. Thus oxido-reductive steps apply for the interconversion of 7[alpha]- and 7[beta]-hydroxy-DHEA through 7-oxo-DHEA. Epimerisation may proceed on the 7-hydroxylated derivatives of EpiA and Adiol through a mechanism involving the cofactor and Ser170.
Stephen O Duke – One of the best experts on this subject based on the ideXlab platform.
phytotoxic and antifungal compounds from two apiaceae species lomatium californicum and ligusticum hultenii rich sources of z ligustilide and Apiol respectivelyJournal of Chemical Ecology, 2005Co-Authors: Kumudini M Meepagala, George Sturtz, David E Wedge, Kevin K Schrader, Stephen O DukeAbstract:
The seeds of two Apiaceae species, Ligusticum hultenii and Lomatium californicum, were investigated. Preliminary bioassays indicated that methylene chloride extracts of seeds of both species contained selective phytotoxic activity against monocots and antifungal activity against Colletotrichum fragariae. Active constituents were isolated by bioassay-guided fractionation, and the structures were elucidated by NMR and GC-MS as Apiol and Z-ligustilide, isolated from L. hultenii and L. californicum, respectively. Apiol and Z-ligustilide had I50 values of about 80 and 600 μM, respectively, for inhibition of the growth of Lemna paucicostata. The methylene chloride (CH2Cl2) extracts of the seeds and the isolated and purified compounds were tested against the 2-methylisoborneol-producing cyanobacterium (blue-green alga) Oscillatoria perornata, and the green alga Selenastrum capricornutum. The CH2Cl2 extracts of both Apiaceae species and Apiol were weakly toxic to both species of phytoplankton, while Z-ligustilide was toxic to both with a lowest complete inhibitory concentration (LCIC) of 53 μM. Seeds of L. californicum and L. hultenii were found to be rich sources of Z-ligustilide (97 mg/g of dry seed) and Apiol (40 mg/g of dry seed), respectively.
Ivonne M.c.m. Rietjens – One of the best experts on this subject based on the ideXlab platform.
Mode of action based risk assessment of the botanical food-borne alkenylbenzene Apiol from parsley using physiologically based kinetic (PBK) modelling and read-across from safroleFood and Chemical Toxicology, 2016Co-Authors: Abdalmajeed M. Alajlouni, Amer J. Al-malahmeh, Reiko Kiwamoto, Sebastiaan Wesseling, Ans E.m.f. Soffers, Ala A.a. Al-subeihi, Jacques Vervoort, Ivonne M.c.m. RietjensAbstract:
The present study developed physiologically-based kinetic (PBK) models for the alkenylbenzene Apiol in order to facilitate risk assessment based on read-across from the related alkenylbenzene safrole. Model predictions indicate that in rat liver the formation of the 1′-sulfoxy metabolite is about 3 times lower for Apiol than for safrole. These data support that the lower confidence limit of the benchmark dose resulting in a 10% extra cancer incidence (BMDL10) that would be obtained in a rodent carcinogenicity study with Apiol may be 3-fold higher for Apiol than for safrole. These results enable a preliminary risk assessment for Apiol, for which tumor data are not available, using a BMDL10value of 3 times the BMDL10for safrole. Based on an estimated BMDL10for Apiol of 5.7-15.3 mg/kg body wt per day and an estimated daily intake of 4 × 10-5mg/kg body wt per day, the margin of exposure (MOE) would amount to 140,000-385,000. This indicates a low priority for risk management. The present study shows how PBK modelling can contribute to the development of alternatives for animal testing, facilitating read-across from compounds for which in vivo toxicity studies on tumor formation are available to compounds for which these data are unavailable.