Biomedical Engineering Reference
In-Depth Information
Fig. 8
Product ion spectra
of diverse tropane alkaloids
after collision-induced
dissociation. Spectra were
obtained after positive
electrospray ionization and
collision-induced
dissociation (CID) with
nitrogen in a QTrap 4000
instrument. Common
structural elements cause
generation of corresponding
diagnostic fragments, e.g.
m
/
z
124 and 93. For
structural assignment of
biotransformation products
similar fragmentation pattern
were produced and
interpreted as shown by
Chen et al. [
6,
7,
51
] and
He et al. [
59
]
a
atropine/
D/L-hyoscyamine
124
.
3
124.3
H
3
C
N
93.1
O
290.2
93.1
O
OH
m/z
b
124.1
124.1
homatropine
H
3
C
N
142.1
93.1
O
93.1
O
276.1
OH
142.1
m/z
c
124.3
124.3
H
3
C
ipratropium
290.1
CH
3
+
H
3
C
N
166.3
93.1
O
93.1
290.1
O
332
.4
166.3
OH
m/z
d
124.1
littorine
124.1
93.2
H
3
C
N
93.2
O
142.2
O
290.1
OH
142.2
m/z
4. The parent drug and its metabolites exhibit different retention times in RP-LC
separation being predictive for altered polarities.
Accordingly, Chen et al. performed a serious number of charming in vivo and
in vitro biotransformation studies for diverse TTA (anisodamine, anisodine,
atropine, scopolamine) after oral administration of the drugs to rat [
5-
7,
51,
52,
87
] .
Urine was analysed by LC-MS/MS methods that provided the following opera-
tion modes:
1. Product ion scan: This type of scan monitors all product ion signals within a pre-
adjusted
m
/
z
range that are produced from a pre-selected precursor ion represent-
ing the expected mass of a postulated biotransformation product. The entire set
of product ions supports interpretation of diagnostic fragments and thus of struc-
tural identi fi cation.
2. Precursor ion scan: Following this detection mode all analyte ions are captured
that generate a specified product ion during CID. With respect to TA structures
the MS/MS signal at
m
/
z
124 could be defined as a common product ion (repre-
senting the tropane moiety) that allows to detect the protonated masses of any
precursor ion that generates this tropane moiety signal. Figure
8
depicts MS/MS
spectra of diverse TA that were obtained after positive ESI and CID. The com-
mon presence of the signal at
m
/
z
124 illustrates that atropine as well as
homatropine, ipratropium and littorine would be detectable by a corresponding
precursor ion scan.
