The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
R A Bastow - One of the best experts on this subject based on the ideXlab platform.
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a note on spectrophotometric methods for the determination of Norethynodrel and mestranol in tablets
Journal of Pharmacy and Pharmacology, 2011Co-Authors: R A BastowAbstract:The method for assay of Norethynodrel involves acid catalysed rearrangement of the Δ5,10 system to a Δ4,3-ketone with stronger ultraviolet absorption. Mestranol is determined from its absorption at 280 mμ after elimination of the interfering ketonic absorption by reduction with borohydride. Residual interference is allowed for by a three point correction.
J F Chissell - One of the best experts on this subject based on the ideXlab platform.
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colorimetric method for the estimation of Norethynodrel in tablets containing mestranol
Journal of Pharmacy and Pharmacology, 2011Co-Authors: J F ChissellAbstract:The colour method proposed for the estimation of Norethynodrel in tablets with mestranol utilises a reaction similar to the well known Zimmerman reaction, the reagents employed being m-dinitrobenzene and benzyltrimethylammonium hydroxide solution and a solvent mixture consisting of ethyl acetate and ethanol. Maximum extinction was at a wavelength of 510 mμ and Beer's law is obeyed for a concentration range 5 to 20μg Norethynodrel per ml final solution.
Richard A Edgren - One of the best experts on this subject based on the ideXlab platform.
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early oral contraceptive history Norethynodrel is not a prohormone
Steroids, 1994Co-Authors: Richard A EdgrenAbstract:A reproductive endocrinologist questions Professor Carl Djerassis long-held claim that Norethynodrel is changed in the body to norethindrone. This conversion circumvents Djerassis patent. Yet biological facts do not support Djerassis claim. The biological properties of both progestagens are different. Norethindrone has weak unusual progestational effects and some androgenic activity. In rats it converts to an estrogen within several days after being ingested orally. Norethynodrel has even weaker and more unusual progestational effects and some estrogenic activity. Neither norethindrone nor Norethynodrel carry out much progestational activity when administered locally in the McGinty assay. Neither support pregnancy in spayed female rats. In the Clauberg test both operate like mixtures of estrogen and progesterone. A series of experiments examining the possibility of gastrointestinal conversion of Norethynodrel to norethindrone conducted by the reproductive endocrinologist did not support the claim that Norethynodrel converts to norethindrone in the body. In fact he is not aware of any evidence that norethindrone is a key metabolite of Norethynodrel. Yet over 40 years of study of oral contraceptives (OCs) the scientific community knows little about the metabolism of these progestagens or others that are now components of OCs. A recent review suggests that norethindrone and ethynodiol diacetate are prohormones that hinge on conversion to norethindrone for their effects. The literature does not support such a conversion of Norethynodrel however. The reproductive endocrinologist also questions why contraception is not part of the norethindrone patent since the goal of early synthetic programs was OCs. The Norethynodrel patent also does not make a contraception claim. In 1952 one of Searles chief scientists called for colleagues to find an orally active progestogen for therapeutic purposes. Later contraception became another goal. How ironic that the weak progestational properties of the first two progestational components of OCs were the basis for their patents.
James D. Yager - One of the best experts on this subject based on the ideXlab platform.
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Oral Contraceptive Steroids as Promoters or Complete Carcinogens for Liver in Female Sprague Dawley
2013Co-Authors: James D. YagerAbstract:Published reports have described an increased incidence of adenomas and of hepatocellular carcinomas in livers of women with a history of long-term oral contraceptive use. Evidence derived from human and experimental animals suggests that oral contraceptive steroids may be liver tumor promoters. Experiments were designed to determine the initiating and/or promoting potential of two oral contraceptive steroids, namely mestranol and Norethynodrel. The results show that: mestranol and Norethynodrel can promote DEN-initiated hepatocarcinogenesis, as indicated by increased numbers of y-glutamyl transpeptidase-positive, putative preneoplastic lesions and by the appearance of carcinomas. Various synthetic estrogens fail to cause detectable levels of DNA damage in hepatocytes. Mestranol has weak, if any, initiating potential. Neither mestranol nor Norethynodrel exhibits antiglucocorticoid activity. Mestranol and Norethynodrel inhibit metabolic cooperation in V-79 Chinese hamster cells. Taken together, these results and those reported by others demonstrate that oral contraceptive steroids are relatively strong promoters of hepatocarcinogenesis and have little if any genotoxic effect
Gengli Duan - One of the best experts on this subject based on the ideXlab platform.
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p toluenesulfonyl isocyanate as a novel derivatization reagent to enhance the electrospray ionization and its application in the determination of two stereo isomers of 3 hydroxyl 7 methyl Norethynodrel in plasma
Journal of Chromatography B, 2005Co-Authors: Ming Zuo, Mingjie Gao, Zhen Liu, Lei Cai, Gengli DuanAbstract:In this paper, p-toluenesulfonyl isocyanate has been reported as a novel derivatization reagent with strong nuclephilic reactivity for the hydroxyl compounds. The derivatization for the two pharmacologically active 3-hydroxyl metabolites, 3alpha-hydroxyl-7-methyl-Norethynodrel and 3beta-hydroxyl-7-methyl-Norethynodrel by p-toluenesulfonyl isocyanate can be accomplished in 2 min under room temperature. The offline derivatization procedure introduced an easily ionizable sulfonylcarbamic ester moiety to the metabolites. This greatly improved the analyte's sensitivity in negative electrospray ionization and enabled us to achieve the desired lower limit of quantitation at 100 pg/ml in plasma. Therefore, a sensitive high performance liquid chromatography-mass spectrometry (HPLC-MS) method for the analysis of the two stereo isomers was developed. The method had been validated to be accurate, precise, and sensitive, and can be used for the metabolism pharmacokinetic study of tibolone in human subjects.
