## 2 Phytochemicals Present in Beetroot
### Phenolic Acids and Flavonoids
This confirmed, although the content of some individual compounds was higher, that the fermentation process decreased the concentration of phenolic acids (45.6% reduction) and flavonoids (27.2% reduction). This reduction could be partially attributed to the activity of phenolic acid decarboxylase and reductases [49]. In addition to those phenolic compounds reported by the aforementioned studies, other authors also identified other phenolic acids, such as p-coumaroylquinic acid, 2-O-(3,4-dihydroxybenzyl)-2,4,6-trihydroxyphenylacetic acid, and theogallin acid, and flavonoids such as quercetin-glucose, A-type dimer of (epi)catechin-(epi)catechin, betagarin, rhammetin, rhamocritin, and astragalin, in beetroot or its products [28; 42]. In general, despite all the phenolic compounds detected, it should be noted that beetroot presents a significant content of rutin [24], which agrees \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Beetroot Material**} & \multicolumn{2}{c}{**Phenolic Compounds**} & \multirow{2}{*}{**Ref.**} \\ \cline{2-2} \cline{4-4}  & **Total Phenolic** & & **Total Flavonoid** \\ \hline Beetroot pulp & 245 mg/100 g & 0.88 mg/100 g & [PERSON] et al. [41] \\ \hline Beetroot leaves & 12.76 mg/g DM & 11.64 mg/g DM & [PERSON] and Angelino [45] \\ \hline Beetroot powder & 292 mg/100 g & - & [PERSON] et al. [46] \\ \hline Fresh beetroot & 1.77 mg/g DM & 1.44 mg/g DM & [PERSON] and Angelino [45] \\ \cline{2-2} \cline{4-4}  & 255 mg GAE/g & 260 mg RE/g & [PERSON] et al. [37] \\ \hline Grated beetroot & 570–920 mg GAE/kg & - & [PERSON] et al. [28] \\ \hline Boiled beetroot & 238 mg GAE/g & 261 mg RE/g & \\ \hline Dried beetroot & 347 mg GAE/g & 230 mg RE/g & \\ \hline Pickled beetroot & 192 mg GAE/g & 173 mg RE/g & [PERSON] et al. [47] \\ \hline Beetroot jam & 231 mg GAE/g & 143 mg RE/g & \\ \hline Beetroot pure & 236 mg GAE/g & 290 mg RE/g & \\ \hline Beetroot juice & 225 mg GAE/g & 126 mg RE/g & \\ \cline{2-2} \cline{4-4}  & 540–810 mg GAE/L & - & [PERSON] et al. [28] \\ \cline{2-2} \cline{4-4}  & 30.8 mg GAE/g DM & 6.72 mg QE/g DM & [PERSON] et al. [20] \\ \cline{2-2} \cline{4-4}  & 0.978 mg GAE/g & 1.42 mg CE/g & [PERSON] et al. [47] \\ \hline Beetroot extract & 20.73 mg GAE/g & 39.75 mg CE/g & \\ \cline{2-2} \cline{4-4}  & 27.2 mg GAE/mL & - & [PERSON] et al. [9] \\ \cline{2-2} \cline{4-4}  & 279–399 mg/L & - & [PERSON] et al. [36] \\ \hline  & 53–65 mg GAE/g & - & [PERSON] et al. [39] \\ \hline DM: Dry matter; GAE: Gallic acid equivalent; QE: Quercetin equivalent; CE: Catechin equivalent; RE: Rutin equivalent. & \\ \end{tabular}
\end{table} 
Table 3: Total phenolic and total flavonoid contents in different beetroot sources. with other authors who concluded that the primary flavonoids in red beetroot are rutin, kaempfer, rhamnetin, rhamnocitrin, and astragalin [42]. Therefore, the results discovered in this review confirm the high phenolic and flavonoid amounts in beetroot and beetroot products. This has a direct impact on the antioxidant and free radical scavenging activity of these products. In this regard, several authors observed a strong correlation between beetroot phenolic content and antioxidant activity [10; 21; 24; 38]. However, as reported in the betalains section, it should be mentioned that betalains exert a synergistic effect with phenolic acids and flavonoids to further enhance antioxidant properties. Finally, other compounds such as carotenoids and ascorbic acid, also contribute to the total antioxidant capacity of beetroot [20]. However, their low content relative to betalains and phenolic compounds make their effect on the antioxidant properties of beetroot comparatively much less.