# Phytochemicals and Antioxidant Properties of Edible Flowers
## 2 Phytochemicals
### Phenolic Compounds
#### 2.1.3 Flavonoids
In the case of _Hibiscus syiacus_ L., the red flowers presented higher TAC than purple and pink, with values of 3.2 mg/g, 1.87 mg/g and 1.61 mg/g (DW), respectively [31]. [PERSON] et al. [30] studied twelve species of cultivated edible flowers and reported the presence of a high TAC up to 14.4 mg cyn-3-glu eq./100 g FW and large variation from 0.35 to 14.4 mg cyn-3-glu eq./100 g FW. The highest concentrations (as mg cyn-3-glu eq./100 g FW) were reported for flowers from _Petunia \(\times\) hybrid_ (red 14.4 mg/100 g; rose 12.9 mg/100 g). _Viola \(\times\) wittrockiana_ (blue 13.6 mg/100 g; red 12.4 mg/100 g), _Dianthus \(\times\) barbatus_ (red 13.4 mg/100 g; rose 10.6 mg/100 g), and _Pelargonium peltatum_ (red 12.5 mg/100 g), while the lowest were reported in white or orange flowers such as _Tagetes ercta_ (orange 0.75 mg/100 g), _Viola \(\times\) wittrockiana_ (white 0.35 mg/100 g), _Dianthus \(\times\) barbatus_ (white 0.73 mg/100 g) and _Calendula officinalis_ (orange 0.47 mg/100 g). In addition, [PERSON] et al. [32] studied twenty-eight species of fresh edible flowers from Sri Lanka using the pH differential method. Concentrations higher than 100 mg cyn-3-glu eq./100 g DW were reported for flowers from _Hibiscus rosa-sinensis_ (200 mg/100 g), _Carrica papaya_ (140 mg/100 g), _Punica granatum_ (118 mg/100 g) and _Ixora coccinea_ (157 mg/100 g), while the lowest concentrations below 3 mg cyn-3-glu eq./100 g DW were reported for flowers from _Cassia auriculata_, _Duriozibethinus_, _Calendula officinalis_ (2 mg/100 g), _Musa_ spp (0.8 mg/100 g) and _Madhuca longifolia_ (0.6 mg/100 g). Some extracts from edible flowers presented important contents of total anthocyanins, and therefore they have been proposed for potential applications in the food industry both for natural colorants and antioxidants. The ethanolic extract (0.01% HCl in 50% ethanol) of Titaniscus (a hybrid of _Hibiscus mosebutos \(\times\) H. occineus_ (Medic.) Walt.) flowers presented total monomeric anthocyanin content (mg Cy3-G/g extract) of 2.7 mg/g for Artemis (white/pink), 6.0 mg/g for Rhea (pink) and 47.1 mg/g for Adonis (red) [33]. Furthermore, the ethanolic extracts of _Viola wittrockiana_ and _Antirrhinum majus_ flowers were 5.7 and 0.3 (\(\mu\)g/mg DW), respectively [34]. Flavones and Flavonones are two classes of flavonoids present in edible flowers. Flavones have the structure of 2,3-dihydro, but without a double bond between C2 and C3, making C2 chiral. On the other hand, flavones contain the double bond between C2 and C3 [8]. In edible flowers, flavanones such as hesperidin, naringenin, isosacuratenin, heridictol and their derivatives and flavones such as luteolin, apigenin, acacetin, chrysoeriol and their glucosides have been detected (Table 7). Flavores, in addition to their functions to help plants to adapt to their surrounding environment, have been also correlated with numerous health benefits in humans, including antioxidant, antimicrobial and anticancer activities [35]. Among 70 edible flower samples in China, flavones were only detected in seven, and mainly apigenin [36]. The highest content was detected in _Tropaeolum majus_ (53.6 \(\upmu\)g/g DW apigenin), followed by _Helichrysum bracteatum_ (10.4 \(\upmu\)g/g DW apigenin and 7.4 \(\upmu\)g/ DW chrysin) and _Matthiola incana_ (10.9 \(\upmu\)g/g DW apigenin). Flavanones derived from edible flowers have been correlated with potential antiaging properties. More specifically, flavanones such as hesperetin, hesperidin, neohesperidin and naringin have been extensively studied for their antiaging properties [37]. In general, flavanones, and especially hesperidin and hesperetin, have been correlated with several health benefits [38]. In a study of the phenolic composition of edible flowers of distinct colors used in foods and drinks, hesperidin and naringenin were the main flavanones [39]. The highest content of flavanones was detected in _Cosmos sulphureus_ Cav. (yellow color and 1661 \(\upmu\)g/g FW) and the lowest in _Begonia_\(\times\)_tubchybrida_ Voss.