## 3 Results and Discussion
In the literature, the following differences in chemical structures were mentioned as the most important in affecting the starch digestibility: (1) the presence of hydroxyl (-OH) groups, which take part in the formation of hydrogen bonds between -OH groups of phenolics and amino acids of the active site of the enzyme (such as Asp197 and Glu233); (2) flavonoids without substitution of -OCH\({}_{3}\) at -OH in their molecular structures, which are more likely to be effective inhibitors of \(\alpha\)-amylase; (3) the 2,3-double bond in the ring C conjugated with the 4-carbonyl group enhances electron delocalization between ring C and A, forming a highly stable conjugated system at the active site of the \(\alpha\)-amylase with strong inhibitory properties; (4) hydrogenation of 2,3-double bond decreases the inhibitory activity (flavanons and flavanols had weaker inhibiting properties than flavonoids and flavones); (5) glycosylation on flavonoids decreases the inhibitory activity; (6) more galloyl groups, resulting in greater inhibitory properties as the galloyl groups provide three hydroxyl groups that might interact with the catalytic site of \(\alpha\)-amylase [26; 27; 28; 30]. Taking into account the above mentioned, the tested polyphenols in this study have been arranged according to their inhibitory activity (Table 3), from excellent to poor. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & ******Excell** & & & **Double Bond** & & & **C = O** & **Additional** \\  & ******Very Good** & **-OH** & **-OCH\({}_{3}\)** & **Conjugated** & **Conjugated** & **Glycolyasted** & **Galloyl** & **Bond in** & **Benzene** \\ \multirow{2}{*}{**Polyphenyl**} & **–** **+ Good** & **Groups** & **Groups** & **with Carbonyl** & **Form** & **Moieties** & **Galloyl** & **Ring** \\  & **–** & **-** & **-** & **-** & **-** & **-** & **-** & **-** \\  & **–** & **-** & **-** & **-** & **-**  
In the presented list, the first two polyphenols expected to have the strongest inhibitory activity, belonging to the flavanols group (epigallocatechin gallate and (+)catechin), were also the most efficient in this study in RS development at three doses (Table 1). This might result from a process of aggregation of hydroxyl groups in the structures of analyzed flavanols. Hydroxyl groups are crucial for the inhibitory activity of flavonoids against \(\alpha\)-amylase and amyloglucidase [27, 28, 30, 32, 33]. Hydrogen bonds between the -OH groups in position R6 or R7 of the A ring and position R4\({}^{\prime}\) or R5\({}^{\prime}\) of the B ring are favorable for interaction of the flavonoid ligand with the side chains of the catalytic center of \(\alpha\)-amylase [27, 30]. The tested anthocyanins (delphinidin-3-O-glucose and cyanidin-3-O glucoside), although positioned quite high in the inhibitory activity list due to many hydroxyl groups [26], were relatively poorly efficient in RS formation at the three doses used in this study (Tables 1 and 2). This might result from the fact that delphinidin-3-O-glucose and cyanidin-3-O glucoside are glycosylated forms of anthocyanin [34] that might decrease their binding affinity to \(\alpha\)-amylase, mainly due to some changes in their spatial structures to bulky non-planar arrangements, limiting their affinity for hydrophobic sites of the enzyme [27, 28]. Flavonols (quercetin, kaempfer) are characterized by good and very good inhibitory activities due to the several -OH groups they contain and additionally the 2, 3-double bond in ring C conjugated with a 4-carbonyl group (Table 3). However, in this study, they were most efficient in contributing to RS formation only at the 5 mg dose (4.76% of starch gel), and then the formation of RS was drastically lowered (Tables 1 and 2). Flavanones (hesperidin, naringenin) are characterized by good and satisfactory inhibitory properties (Table 3) and favor the formation of RS to the greatest extent at the 5 mg dose, but at the higher doses (10 mg--9.09% of starch gel, 20 mg--16.66% of starch gel), the effect was not further observed (Tables 1 and 2).