3.2.6. Flavonoids

Peak 43, [M−H]<sup>−</sup> = 595.1303 (C26H27O16) showed (Figure 11) fragments at *m*/*z* 300 and 301, coincident with a quercetin aglycone. Thus, this peak was identified as quercetin-3-*O*-pentosylhexoside. Peaks 49 and 50 were identified as isomers of quercetin 3-*O*-hexoside, due to their [M−H]<sup>−</sup> ion at 463.0893 (C21H19O12) and the fragment at *m*/*z* 301 ([M−H−162]<sup>−</sup>, loss of hexoside). Similarly, peaks 52 and 53 ([M−H]<sup>−</sup> = 433.0786, C20H17O11) had the same fragment at *m*/*z* 301 [M−H−132]<sup>−</sup> due to the loss of a pentoside, so they were identified as isomers of quercetin 3-*O*-pentoside [19].

Peak 62 had an [M−H]<sup>−</sup> ion at 609.1467, consistent with the molecular formula of C27H29O16. Its main MS2 fragments at *m*/*z* 314 and 315 sugges<sup>t</sup> the presence of a rhamnetin aglycone, so it was assigned to rhamnetin *O*-pentosylhexoside [51]. Peak 68, with [M−H]<sup>−</sup> = 447.1054, C22H21O12, was identified as rhamnetin *O*-hexoside, due to its MS2 fragment at *m*/*z* 315 (loss of hexoside) [19] while peak 71 ([M−H]<sup>−</sup> = 315.0513, C16H11O7) was identified as the aglycone rhamnetin, with a main fragment at *m*/*z* 271 coincident with previous reports [52,53].


**Figure 11.** Structure and fragments of flavonoids.

Regarding the total number of polyphenols in *M. indica* Keitt and T. Atkins cultivars, 149 compounds were found, comprising 12 xanthonoids, 32 phenolic acids and derivatives, 10 hydroxybenzophenones, 10 flavonoids, and 85 gallates and gallotannins. T. Atkins skins have a greater number of compounds than Keitt skins, which exhibit the highest number of gallates and galloltannins with 32 different compounds. In respect to compound diversity, gallotannins are the most recurrent group of polyphenols in both Keitt and T. Atkins skin samples and in Keitt flesh while phenolic acids are the most abundant group in T. Atkins flesh. Xanthonoids are present in all skin and flesh samples and the other two subfamilies differ in their occurrence. For instance, flavonoids are more abundant in T. Atkins skin while hydroxybenzophenones are found only in the skins of both cultivars.

When comparing reports from the literature, our findings coincide with previous reports on Keitt and T. Atkins cultivars from Brazil and Spain [15,17,20,54] showing that skins have a higher number and diversity of polyphenols than flesh and also that Keitt skin and flesh show a similar phenolic profile while the T. Atkins cultivar shows a different profile, with very low diversity for flesh. On the other hand, our results for the Keitt cultivar, which has been given more attention in the literature, indicate a higher number and diversity of compounds than those reported for cultivars from China, Spain, and the USA [13,19,21], particularly in xanthonoids and gallate and gallotannins, with similar results to other reports on cultivars from Spain [20,54].

On the other hand, when comparing the reports for other cultivars in the literature, our results for Keitt and T. Atkins skin cultivars from Costa Rica show a greater number and diversity of polyphenols than the findings on 18 cultivars from Australia, Kenya, Peru, and Thailand [17], as well as from Brazil [55], China [21], and Spain [19], and similar results to the Sensation cultivar from Spain [54]. In the case of flesh, T. Atkins results are similar to cultivars from Mexico and Haiti [8] and higher than those for the Haden cultivar from Brazil [55], while Keitt flesh shows greater and more diverse results than for the other nine different cultivars from Peru and Thailand [17]; as well as from Brazil [55], Mexico, and Haiti [8]; and similar results to the Sensation cultivar from Spain [54].

Finally, our findings for Costa Rican cultivars indicate an important number of gallotannin oligomers of a higher polymerization degree in both Keitt and T. Atkins skins as well as in Keitt flesh; for instance, galloyl hexose decamers and undecamers that are reported for the first time for these two cultivars. These results are of special interest due to reports showing an enhancement of anti-inflammatory and anticancer activities, with gallotannins' higher degree of polymerization, for instance, showing better results than dimers or the galloyl hexose monomer [22].
