## 4 Discussion
Besides, in recent decades, several plant extracts have been scrutinized for their in vitro antichoinesterase activity, with plant species producing diverse classes of alkaloids, coumarins, terpenes, and polyphenols demonstrating the most potent results and hence are potential candidates for new anti-AD drugs. Besides, several studies have been carried out to identify and isolate natural molecules applicable for the design and development of new anti-AD drugs [38; 39]. Melanin, a major pigment found in mammalian skin, is recognized to protect the skin against the detrimental effects of ultraviolet irradiation, oxidative stress, and DNA damage. However, buildup or excessive production of melanin can result in an esthetic problem and severe diseases allied with hyperpigmentation [40]. In this regard, as the key and rate-limiting enzyme for melanogenesis, tyrosinase has been considered an important target for developing therapeutic agents against pigmentation disorders [41]. Tyrosine inhibitors are commercially available for cosmetic uses as skin lightening agents. At the same time, they are clinically employed in treating a variety of hyperpigmentation conditions such as senile lentigines, melasma, and freckles [42]. They are equally applicable as anti-browning agents in the food processing industry. Indeed, this enzyme is responsible for the undesired browning of fruits and vegetables. Therefore, several extensively studied anti-tyrosine effects have been successfully marketed, including synthetic, semi-synthetic, and natural origins. These compounds are from several chemical classes, i.e., phenolics, terpenes, flavonoids, alkaloids, long-chain fatty acids, coumarins, etc. [43; 44]. In this study, the methanolic extracts showed the most potent anti-tyrosinease effect, indicating the presence of key compounds active against tyrosinase. This could be due to their higher phenolic and/or flavonoid contents, which were reported to have a tight correlation with anti-tyrosinease activity. In particular, a strong correlation was observed for anthocyanins, flavones, and phenolic acids, which were also found to be enriched with methanolic extracts. In accordance, previous studies have shown a significant relationship between total phenolic content and anti-tyrosinease activity [45]. The inhibition of tyrosinase activity might depend on the hydroxyl groups of the phenolic compounds of the extracts that could form a hydrogen bond to a site of the enzyme, leading to lower enzymatic activity. Some tyrosinase inhibitors also act through hydroxyl groups that bind to the active site of tyrosinase, inducing steric hindrance or distorted conformation [46; 47]. \(\alpha\)-glucosidase and \(\alpha\)-amylase are the important enzymes involved in the digestion of carbohydrates. \(\alpha\)-amylase is involved in the breakdown of long-chain carbohydrates, whereas \(\alpha\)-glucosidase breaks down starch and disaccharides into glucose. Thus, they are regarded as the major digestive enzymes involved in intestinal absorption. Accordingly, \(\alpha\)-amylase and \(\alpha\)-glucosidase inhibitors are the potential targets for the treatment of diabetes [48]. Interestingly, the _R. angustifolius_ extracts showed a great inhibition capacity of both enzymes. Specifically, the highest anti-amylase and anti-glucosidasease activities were found in ethanolic extracts using maceration and the Soxhlet extraction method, respectively. The inhibition capacity was highly correlated to polyphenols and terpenoids classes. It is well known that plant foods rich in polyphenols have been reported to cause effects comparable to insulin in glucose utilization and can act as good inhibitors of key enzymes such as \(\alpha\)-amylase and \(\alpha\)-glucosidase associated with type 2 diabetes and lipid peroxidation in tissues [48]. Polyphenolic compounds may diminish the potency of \(\alpha\)-amylase and \(\alpha\)-glucosidase by interacting or inhibiting specific positions in the enzymes [49].