## 4 Discussion
The more hydroxyl groups polyphenol has, the more hydrogen bonds between them and amino acids of the enzyme can be created. As a consequence, the inhibition of \(\alpha\)-amylase activity is stronger. Moreover, epigallocatechin gallate, as the only one from the tested polyphenols, contains a galloyl moiety. It provides additional hydroxyl groups, a benzene ring, and the C=O double bond. An extra benzene ring can create hydrophobic interactions within the enzyme's active site. The C=O double bond, when conjugated with the benzene ring, plays a role in electron delocalization. All this together forms a highly stable conjugated system that further enhances the inhibitory activity of the polyphenol. Additionally, in the molecular structure of epigallocatechin gallate, there is no substitution of -OCH3 at -OH and no presence of the glycosylated form. It also increases the polyphenol's inhibitory activity on starch digestibility [37; 64]. The current study also confirmed that epigallocatechin gallate exhibits the greatest inhibitory activity. The polyphenol demonstrated the greatest efficacy in reducing the RDS, TS, and eGI values of all the tested starches. Furthermore, the greatest outcomes were typically observed when the highest dose tested (20 mg) was administered, despite the recommended daily intake of polyphenols being 10 mg [53]. The low value of RDS slows down the process of digestion because the lower the fraction is, the less glucose is released into the bloodstream rapidly after meal consumption [10; 65]. Epigallocatechin gallate also had the greatest impact on lowering TS content, and it seems the reason for this is the establishment of non-digestible complexes between the polyphenol and starch granules [12]. Epigallocatechin gallate has a strong ability to alter the spatial configuration of starch, with highly consistent hydrogen bond occupancy and low binding free energy [66]. The highest efficiency in reducing RS content in wheat starch was observed with a dose of 5 mg of quercetin when the polyphenol was added after starch pasting (\(p<0.05\)). The precise value was determined to be 3.33 g\(\cdot\)100 g\({}^{-1}\) d.m. In the preliminary investigation wherein the digestibility of wheat starch was assessed through the measurement of RS (polyphenol addition after starch gelatinization), the exact value was established to be 3.89 g\(\cdot\)100 g\({}^{-1}\) d.m. However, the preliminary study yielded a higher value when 5 mg of (+)catechin was added (4.89 g\(\cdot\)100 g\({}^{-1}\) d.m.) [37], whereas the current study demonstrated an RS content of 0.68 g\(\cdot\)100 g\({}^{-1}\) d.m. with the same quantity of (+)catechin. The inhibitory activity of both quercetin and (+)catechin was evaluated as being highly potent based on their molecular structure [37; 64]. In the present study, (+)catechin was observed to be less effective than quercetin in the preliminary study. The addition of (+)catechin in a dose of 20 mg to rice starch after its pasting was found to be the most effective method for reducing RS (\(p<0.05\)). Quercetin in a dose of 10 mg, on the other hand, was the most effective polyphenol for reducing SDS and SDI in rice starch when added after its pasting (\(p<0.05\)). Additionally, the SDS of potato starch was reduced to the greatest extent by adding the polyphenol at a dose of 20 mg before pasting, while the RS of maize starch was reduced to the greatest extent by adding the polyphenol at a dose of 20 mg after pasting (\(p<0.05\)). The highest RS content in wheat starch was recorded simultaneously with the addition of hesperidin at a dose of 10 mg after starch gelatinization (3.31 g\(\cdot\)100 g\({}^{-1}\) d.m., \(p<0.05\)). This result is comparable to that obtained in the preliminary study, in which the highest RS content was observed for epigallocatechin gallate (2.86 g\(\cdot\)100 g\({}^{-1}\) d.m.) and hesperidin, which yielded an equal result of 1.42 g\(\cdot\)100 g\({}^{-1}\) d.m. [37].