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Dear all,
I meet a bioanalytic problem. Any suggestion is appreciated.
I am analyzing a derivative of 1,4-naphthoquinone (compound A). I
tried the methods I could think out, but there was no expected result.
1. In vitro study \0x00the compound was added to fresh rat plasma
(concentration was up to 10\0x00g?ml-1), and then extracted by Hexane
\0x00recovery rate was 42.6%\0x00but when plasma was replaced by
blood, no parent drug could be detected.
2. The compound was administrated to Rats (po.), blood sample were
collected respectively after 30min,60min,120min, part of blood sample
were used to prepare plasma sample. Methods of deproteinization (CH3CN
\0x00MetOH), liquid-liquid extraction (Hexane, EtOAc\0x00CHCl3
\0x00tertiary butyl methyl ether\0x00ethyl ether), strong acid ,
neutral salt were used to study on the extraction of compound A from
plasma or blood sample ,no parent drug was detected by HPLC.
3. EDTA-2Na and pH regulation were also uesd , but parent drug was
still undetectable.
4. It was supposed that compound A could covalent with Sulfur
Nucleophiles of Proteins\0x00so dithiothr eitol\0x00Guanidine
thiocyanate \0x00mercaptoethanol were used to treat with blood or
plasma sample. The results were as follows: neither parent drug nor
product of reaction was detected by HPLC in blood sample after the
treatment of dithiothr eitol; Guanidine thiocyanate couldn't react
with compound A\0x00the detection sensitivity of product of reaction
between compound A and mercaptoethanol in blood sample was low, and
it couldn't meet with quantitative requirements.
The basic information for this compound:
C21H22O6; Mol.wt: 370.40;
Solubility:
soluble in ethyl ether\0x00hexane, EtOAc,CH3CN\0x00CHCl3\0x00MeOH.
poor water- solubility.
Stability:
The N,N-dimethylacetamide solution of the compound was completely
decomposed with natural light for 5 hours. The compound was unstable
at alkaline condition.
Thanks in advance.
Ma Guangli
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The following message was posted to: PharmPK
Have you looked for epoxynapthoquinone, napthalenediol and related
oxidative metabolites in blood/plasma?. BSA can catalyze oxidation of
napthoquinone in blood and plasma.
Sandeep
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Dear sandeep and Venkatesh,
Thank you for your helpful suggestions.
sandeep, would you give me some hints on how to look for such
metabolites in blood/plasma?
Venkatesh, you are right ,this compound is poorly water soluble, high
lipophilic and high affinity towards to the plasma protiens. I tried
the llE methods you mentioned ,but no parent drug was detected. For
your Solid Phase extarction method, after 0.5 ml plasma+ drug+ add
0.5 ml ACETONITRILE, dry the supernatant under nitrogen, but no
parent drug was detected. The problem still exist......
Yours
Ma Guangli
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The following message was posted to: PharmPK
Dear Ma Guangli,
Please look for any modifications of +14, 16, 18, etc. to your parent
compound. If you have a triple quad you can also perform precursor ion
scans (PIS) and neutral loss scans (NLS) based upon the product ion scan
of your parent compound. The product ion scan for the parent compound
can be generated during tuning the instrument for MS/MS. The MRM
parameters you obtain during tuning can be used for setting up the
precursor ion scan/neutral loss scan experiments. You can also further
modify the masses by adding +14, +16 etc to the fragments to determine
any metabolites with modifications to the corresponding fragments from
the parent compound. There may be other functional moieties in your
molecule apart from the napthoquinone that could be unstable in plasma.
So, my suggestions would be:
1. Tune the parent compound in the MS/MS mode - Gives you MS/MS
parameters that you can use for setting up PIS, NLS.
2. Perform a full scan - Gives you an idea about potential metabolites.
3. Product Ion scan - based on metabolites masses observed in full scan
mode
4. Precursor ion scan - gives you metabolites that undergo fragmentation
to the selected precursor ion.
5. Neutral loss scan - gives you metabolites that lose the same neutral
mass as the parent.
It is more than likely that after full scan and product ion scan you
will have all the information you need and not have to perform PIS and
NLS.
Regards,
Sandeep
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