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The following message was posted to: PharmPK
Dear All,
I am working on an NCE since few days. In my plasma chromatograms run
on HPLC on reverse phase column, I am finding a peak just before my
drug peak. After checking the mass of the peak and comparing it with
the mass of the parent peak we found that 14 amu is getting added to
the parent compound.When in-vitro metabolism was carried out in rat
liver microsomes, we are not findingabove mentionedmetabolite. So, we
suspect it to be a phase 2 product.As nitrogen atoms are present in
the structure , we suspect it to be a phase 2methylatedconjugate of
the parent drug.
Havingsaid that I want to know what is the means by which I can
carryout the methylation reaction in-vitro usingrat liver
microsomes.In case ofglucuronidation if wesupplement the rat liver
microsomeand drug mixture withUDP-glucuronic acid , we can get the
glucuronidated product. In the sameway I came to knowform the
literature that methylation can be done in presence
ofS-adenosylmethionine, which acts as amethyl donor. But I couldn't
get the protocol.Can anybody suggest references where such type of work
is carried out.
Thanks
From
Ravi Kanth
Ravi Kanth Bhamidipati
Senior Pharmacologist
Dept.of Drug Metabolism and Pharmacokinetics
Discovery Research Division
Dr.Reddy's Laboratories Ltd.
Bollaram Road , Miyapur
Hyderabad - 500 050
Andhra Pradesh
India
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The following message was posted to: PharmPK
Dear Dr.Kishore,
Thanks for your prompt reply. Basing on the information sent by you, I
have gone through Sigma Aldrich website for procuringadenosyl
methionine. The S-adenosyl-L-methionine I found in the sigma catalogue
was cathechol-O-methyl transferase. Will the same one transfer the
methyl group onto nitrogen atom or to that matter any other
atompresent inside chain or in the ring.
Regards,
Ravi Kanth Bhamidipati
Ravi Kanth Bhamidipati
Senior Pharmacologist
Dept.of Drug Metabolism and Pharmacokinetics
Discovery Research Division
Dr.Reddy's Laboratories Ltd.
Bollaram Road , Miyapur
Hyderabad - 500 050
Andhra Pradesh
India
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The following message was posted to: PharmPK
Ravi,
When I performed a brief study of N-methylation I used a protocol based
upon that described by
Ansher & Jakoby (1986) "Amine N-Methyltransferase from Rabbit Liver" (J.
Biol. Chem. 261, 3996-401).
Although this is a little old, as well as giving assay details it gives
a
nice summary of the biology
and substrate specificity of the enzymes and methods for their
purification.
All the very best,
Bernard
Bernard Murray, Ph.D.
Senior Pharmacologist
Drug Metabolism, PCS, PPD, GPRD, Abbott Laboratories, Chicago, USA
Bernard.Murray.-a-.abbott.com
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