## 4 Discussion
Indeed, the antioxidant properties of plant foods have mainly been attributed to their rich phenolic contents. In particular, antioxidants play their protective role on cells either by preventing the formation of free radicals or by neutralizing/scavenging free radicals produced in the body, or by reducing/chelating the transitional metal composition of food [29]. The antiradical activity of flavonoids and phenols is principally based on the structural relationship between various parts of their chemical structure [30]. It has been found that a high and significant (\(p<0.01\)) correlation coefficient exists among flavonoids and DPPH, ATBS, CUPRAC, and FRAP capacities. Moreover, in the present study, the ethyl acetate extracts showed lower antioxidant activity and contained fewer phenolic compounds and flavonoids than the methanolic extracts, which agreed with the study of [23]. The antioxidant effect of flavonoids could be attributed to their chemical structure, indicating that the presence of \(3^{\prime}A^{\prime}\)-catechol, and \(4^{\prime}\)-OH groups on the B ring were highly correlated with the antioxidant capacity [31]. Accordingly, our findings include many flavonoids, particularly in HAE-MetOH extracts, including kaempfer, morin, myricetin, quercetin, and their 3-O, 4-O, and 7-O glycoside groups (Table S1). Other Rhinanthus species, including \(R\). _angustifolius_, possessed notable antioxidant activity [2; 32]. In the last years, the food industry is searching and developing healthier and more nutritious foods. In this regard, functional food ingredients have attracted much attention as their dietary intake has been associated with preventing different chronic diseases. Indeed, enzyme inhibitors have become a crucial aspect of the food industries in producing functional foods, as they have a preventive purpose for human health. Enzymes take part in a wide range of human ailments, and several specific enzyme inhibitors have been designed to combat their activities, therefore acting as therapeutic agents [33]. The present work investigated the inhibition properties of \(R\). _angustifolius_ extracts against acetyl- and butyryl-cholinesteraseerases, tyrosinase, amylase, and glucosidase enzymes. Cholinergic deficiency is associated with Alzheimer's disease (AD), and various cholinesterase inhibitors have been developed to treat AD, including naturally derived inhibitors, synthetic analogs, and hybrids. Currently, the available drugs for AD are predominantly cholinesterase inhibitors. However, the efficacy of these drugs is restricted as they may cause adverse effects and cannot fully arrest the progression of the disease [34]. Acetylcholinesteraseerase (AChE) is the most crucial enzyme regulating the acetylcholine level in the healthy brain, while butyrylcholinesteraseerase (BChE) plays a minor role. In patients with AD, the level of AChE activity reduces, and the activity of BChE increases, such that the ratio between BChE and AChE can alter from 0.6 in the normal brain to as elevated as 11 in cortical areas affected by the disease. For that reason, inhibition of AChE and BChE is the most effective therapeutic approach to treat AD symptoms [35]. Regarding our extracts, flavonoids were detected to have a high correlation coefficient with the inhibition of AChE enzyme activity. This result was also confirmed by [PERSON] et al. [36], who revealed the ability of flavonoid compounds in inhibiting antichoinestexase activity in a concentration-dependent manner, particularly quercetin (flavonols), and its glycosylated conjugation reported the highest capacity. Instead, the inhibition of BChE enzyme activity was observed by the action of triterpenes, which reported a high correlation coefficient. Overall, a wide collection of extracts from medicinal plants used in traditional healing systems to improve cognitive function and their derived phytochemicals have shown promising CheE-inhibiting activities [37].