CHARACTERIZATION OF DESERT DATE (Balanites aegyptiaca)

Figure 2.3d shows the negative-mode MS 2 fragment ions of the parent ion at m/z 1209.
The major fragment ion peaks observed in this precursor ion are at m/z 1077, 1063, 915,
769, 589, and 431. The mass differences between the parent ion at m/z 1209 and the
fragment ions at m/z 1077 and m/z 1063 are 132 Da and 146 Da. This shows the loss of a
pentose (xylose) and a deoxyhexose (rhamnose). This also suggests that there are two such
sugars in the terminal residue of the saccharidic chain. However, the high intensity of the
1077 ion indicates that first expulsion of xylose unit from the parent ion at m/z 1209. The
fragment ions from m/z 1077 to 431, inclusive, give the same pattern of sugar-unit loss as
the previous ion 1077 (Fig 2.3c). This suggests that this saponin peak is a very similar
saponin to that of the main MW 1064, with an additional xylose and methyl unit.
The [M-H] - ion MS 2 spectra of the peak ion at m/z 1045 is presented in Figure 2.3e.
These spectra show that there are two main cleavages from the parent ion, at m/z 901 and at
m/z 883, with a deletion of 144 and 162 Da from the parent ion, respectively. The intensity
of the peak at m/z 883 is much greater than that at m/z 901, which demonstrates that the [M-
H] - parent ion at m/z 1045 preferentially jettisons a 162-unit glucoside (glucose). The next
fragment ion, at m/z 737, shows a loss of 162 Da (glucose) plus a loss of 146 Da
(rhamnose) from the parent ion. The fragment ion at m/z 593 shows a further loss of 144
Da. This is 2 Da smaller than a rhamnose molecule and thus is not rhamnose. The
elimination of 144 Da, corresponding to cleavage of the E-ring, is generally observed in
furostanol saponins. Such a cleavage phenomenon has also already been reported by Liang
et al. (2002) and Liu et al. (2004) in a furostanol saponin of Asparagus cochinchinensis.
Thus, this fragmentation pathway suggests that this peak is a genuine furostanol saponin.
The smallest fragment ion, at m/z 431, shows further elimination of a glucose unit (162 Da)
from the fragment ion at m/z 593. As with most of the other parent ions, this ion (m/z 1045)
could not expel a sequential glucoside to produce the [Aglycone-H2O] - ion (m/z 413).
Actually, LC-ESI-MS analysis of the methanol extract of B. aegyptiaca mesocarp
produced eight peaks (Figure 2.1a). Among these eight peaks, we have discussed the
MS/MS analysis of the five major peaks—in terms of area—at 4.2 (m/z 1195), 4.8 (m/z
1063), 7.2 (m/z 1209), 8.2 (m/z 1077), and 12.4 (m/z 1045) min retention time. The other
three peaks, at 6.0, 9.6, and 11.1 min retention time, repeat the values of m/z 1077 and
27