Methoxy groups, detection

Adapted from Kariya et al. (1997). With permission from Elsevier Publisher. a Partially methylated alditol acetate with methoxy groups at the positions shown. b Retention time on a SP2330 capillary column relative to 2,3,4-tri-O-methyl-fudtol. c The molar ratios were based on the peak area. d Not detected. 

Residues in liver of poultry sacrificed at 6 h after withdrawal, were comprised of unchanged semduramicin at a percentage of 45%, whereas an array of more polar, low-level ( 0.1 ppm) metabolites could be also detected. Using bile as a source of major semduramicin metabolites, the metabolism of semduramicin was spectrometrically determined to proceed by (9-demethylation of the methoxy groups in the A and G rings, as it has been also described for maduramicin (30, 31) and monensin (21, 44). 

Finally, it should be noted that while 2-methoxy-3,5-dinitropyridine yields 9, rather than 10, by undergoing attack at the CH position 6, the CH position 4 is attacked by CH30 when both positions 2 and 6 are occupied by a methoxy group to yield 13. Of course, adduct 10 may be formed in DMSO-rich media and escape detection because its conversion to 9 is very fast. 

Incomplete hydrolysis of the methoxy groups is detected in a thin SAAPS film adsorbed onto a zinc substrate after hydrolysis according to the manufacturer s specifications. 

Papaver Alkaloids.—Biosynthesis of morphine (36) occurs, in Papaver somniferum, through reticuline (33) by way of thebaine (35). The sequence from (35) to (36) involves, inter alia, two O-demethylations, with that at the methoxy-group at C-6 occurring first.1,2 Confirmation that the other methoxy-group is not demethylated first in this Papaver species obtains from the failure to detect oripavine (37), which is found in other Papaver species, as a natural constituent of P. somniferum. The experiment involved attempted isolation of radioactive (37), using inactive alkaloid as carrier, following a feeding experiment with radioactive reticuline (33).37... 

APCI has become a popular ionization source for applications of coupled HPLC-MS. Figure 1.33 shows an example of an application of HPLC-APCI coupling [79]. It shows the analysis obtained from extracts of maize plants. Six compounds are identified by mass spectrometry. These compounds have been identified as glucoconjugated DIMBOA (2,4-dihydroxy-7-methoxy-l,4-benzoxazin-3-one) and similar molecules that differ by the number of methoxy groups in the benzene ring and/or by the N-O methylation of the hydroxamate function. This example clearly shows the influence of the analyte on the type of observed molecular species. Indeed, the presence of an acidic group in the compound from peak 1 allows mainly the detection of deprotonated molecular ions, whereas the compound from peak 4 does not contain an acid group and thus leads only to the formation of adduct ions. 

Disposition in the Body. Rapidly absorbed upon inhalation blood gas partition coefficient about 2.4. It accumulates in adipose tissue. About 60 to 80% of an absorbed dose is exhaled unchanged from the lungs in 24 hours and smaller amounts continue to be exhaled for several days or weeks. A variable amount is metabolised in the liver by debromination and dechlorination replacement of a fluorine atom by a methoxy group followed by glucuronic acid conjugation occurs to a limited extent. Other metabolites which have been detected in expired air and in blood are 2-chloro-1,1,1-trifluoroethane and 2-chloro-l, 1-difluoroethylene. Up to about 20% of a dose may be excreted in the urine as trifluoroacetic acid and its salts. Bromide ion is slowly excreted in the urine. 

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