## 4 Discussion
Chlorogenic and caffeic acids are secondary phenolic metabolites produced by tea, green roasted beans, coffee, berry fruits, cocoa, citrus fruits, apples, and pears and have been found at higher contents in purple carrots in respect to differently colored varieties, with the first one representing 72.5% of the total phenolic compounds [36; 37]. The observed two-fold increase of caffeic and chlorogenic acids, as well as the increase of about 30% of luteolin 7-O-glucoside content from November to December, makes the latter month suitable as the optimal harvest time due to the particularly high content of these bioactive compounds withrecognized beneficial activities for health like antioxidant, anti-inflammatory, anti-obesity, antidiabetic, and antihypertensive activities [38; 39; 40]. Finally, to investigate the optimal harvest time, we analyzed the purple carrots after an additional month of cultivation, as a bitter taste in this cultivar is known to develop due to overripening. It is also known that this taste is usually associated with the presence of bioactive compounds [41]. This change in their sensorial properties makes late-harvested carrots unsuitable for consumer consumption, but they could be employed as a source of bioactive compounds. Indeed, our results (Table 2) showed an increase in GABA, chlorogenic acid, luteolin-7-O-glucose, and polyacetylenes content and a decrease in branched amino acids and polyunsaturated \(\omega\)-6 fatty acid. These metabolic trends could be induced by an abrupt change in environmental conditions. In fact, we must remember that the fifth month of cultivation corresponds to the month of December, which is characterized by both autumnal abundant rain and an abrupt drop in temperature in the Fucino area (www.meteoam.it). Due to the rain, the bacterial and fungal charge in the soil could increase [42], and the plant could respond by producing phenylpropanoids, which have antibacterial properties, and polyacetylenes, which have antifungal activity [43; 44]. The increase in polyacetylenes is correlated with the decrease in polyunsaturated \(\omega\)-6 fatty acid levels in carrots since they are the precursors of both falcarinol and falcarindiol [45]. Both molecule classes are also known to confer a bitter taste to foods and, as such, are the origin of this flavor in late-harvested carrots. Furthermore, it has been demonstrated that waterlogging reduces oxygen availability in the soil, causing severe stress to the roots that respond through the activation of the GABA shunt pathway [46; 47; 48; 49]. The activation of this pathway in purple carrot roots is supported by the observed increase in GABA, alanine, and formic acid and the decrease in aspartic acid levels from November to December. In agreement with our hypothesis, the trend of these molecules has been reported to be a consequence of different hypoxic treatments in almost all the studied species [50]. More specifically, it has been proposed that alanine synthesis could represent a defense mechanism that decreases the excess pyruvate produced in anaerobic conditions and pyruvate metabolization to avoid the increase in lactic acid and ethanol in hypoxia [51].