3.2.3. Gallotanins

As represented in Figure 7, compounds 4 and 8 (galloyl *O*-hexose isomers) show an [M−H]<sup>−</sup> ion at *m*/*z* 331.0671 (C13H15O10), with a main fragment at *m*/*z* 169 corresponding to gallic acid. Peak 5 was identified as galloylquinic acid as it had an [M−H]<sup>−</sup> ion at *m*/*z* 343.0667 (C14H15O10) and a fragment *m*/*z* 191 consistent with quinic acid due to loss of galloyl [19] Peaks 2, 3, and 7 with an [M−H]<sup>−</sup> ion at *m*/*z* 493.1214 (C19H25O15) were assigned to galloyl *O*-sucrose due to the MS2 fragment at *m*/*z* 313, consistent with a loss of an *O*-hexoside, and MS3 fragment at *m*/*z* 169 corresponding to gallic acid (loss of second hexoside) [46].

Peak 13, [M−H]<sup>−</sup> 357.0834 (C15H17O10), showed a main MS2 fragment at *m*/*z* 169 and an MS3 fragment at *m*/*z* 125, which is consistent with gallic acid, thus this peak was tentatively assigned to methyl gallate [19]. Peak 15 (di-*O*-galloyl quinic acid) had an [M−H]<sup>−</sup> ion at *m*/*z* 495.0794 (C21H19O14), with a main fragment at *m*/*z* 343 due to the loss of a galloyl. A subsequent loss of quinic acid gives a fragment at *m*/*z* 169 [47]. Peak 21 was identified as hydroxybenzoyl galloyl hexoside due to its [M−H]<sup>−</sup> ion at 451.0900 corresponding to a molecular formula of C20H19O12. The MS2 fragment at *m*/*z* 313 occurs due to a loss of hydroxybenzoyl, and MS3 at *m*/*z* 169 to subsequent loss of hexoside [20].


**Figure 7.** Structure and fragments of gallate derivatives.

Peaks 11 and 20 had an [M−H]<sup>−</sup> ion at 483.0799 (C20H19O14), with a main MS2 fragment at *m*/*z* 169, consistent with di-*O*-galloyl hexose isomers [19].

A series of peaks (Figure 8) were identified as poly-*O*-galloyl hexoses due to their MS2 fragments at [M−H−170]<sup>−</sup> (loss of O-galloyl) and [M−H−152]<sup>−</sup> (loss of galloyl), and MS3 fragment at [M−H−170−152]<sup>−</sup> due to the loss of a subsequent galloyl. This analysis allowed identification of peaks 19, 22, and 29 ([M−H]<sup>−</sup> = 635.0888, C27H23O18) as tri-*O*-galloyl hexose; peaks 31, 32, 40, 41, 44, and 45 ([M−H]<sup>−</sup> = 787.1008, C34H27O22) as tetra-*O*-galloyl hexose; and peak 51 ([M−H]<sup>−</sup> = 939.1132, C41H31O26) as penta-*O*-galloyl hexose [20].

Compounds with more units of gallate in their structures show an MS2 fragment at [M−H−152]<sup>−</sup> due to loss of galloyl, and loss of a second galloyl gave an MS3 fragment at [M−H−152−152]<sup>−</sup>. Therefore it was possible to identify peaks 54, 55, and 56 ([M−H]<sup>−</sup> = 1091.1238, C48H35O30) as hexa-*O*-galloyl hexose isomers; peaks 57, 58, and 59 ([M−H]<sup>−</sup> = 1234.1351, C55H39O34) as hepta-*O*-galloyl hexose isomers; peaks 60 and 61 ([M−H]<sup>−</sup> = 1395.1466, C62H43O38) as octa-*O*-galloyl hexose isomers; peaks 63 and 64 ([M−H]<sup>−</sup> = 1547.1576, C69H47O42) as nona-*O*-galloyl hexose isomers; peaks 65 and 66 ([M−H]<sup>−</sup> = 1699.1690, C76H51O46) as deca-*O*-galloyl hexose isomers; and peaks 67, 69, and 70 ([M−H]<sup>−</sup> = 1851.1819, C83H55O50) as isomers of undeca-*O*-galloyl hexose isomers [15].

**Figure 8.** Structure and fragments of gallotannins.
