Anthocyanins exert potent inhibitory effects on starch-digesting enzymes, primarily α-amylase and glucosidase, through direct molecular interactions and structural alterations. This study elucidates the underlying mechanisms by which anthocyanins reduce enzymatic activity, providing a foundation for designing functional foods with improved glycemic control. Competitive inhibition was confirmed via Lineweaver-Burk plots, indicating that anthocyanins bind reversibly to the active sites of both enzymes, thereby blocking substrate access. The inhibition efficiency increased with anthocyanin concentration, reaching a maximum of 45.39% for α-amylase and 20.08% for glucosidase at 0.5 mg/mL, suggesting stronger affinity toward α-amylase.
Molecular docking simulations revealed that cyanidin-3-glucoside, the predominant anthocyanin in black rice, forms stable complexes with both enzymes.C2orf69 Antibody supplier In α-amylase, the molecule fits within the catalytic cleft, forming hydrogen bonds with key residues such as His201, Glu233, Asp300, Trp59, and Gln63. These interactions stabilize the inhibitor-enzyme complex and prevent proper substrate positioning. Similarly, in glucosidase, cyanidin-3-glucoside binds to the active site pocket, engaging in hydrogen bonding with Asn424 and Asp431, which are critical for maintaining enzyme conformation. The binding energy calculations indicated strong interaction affinities, supporting the competitive inhibition model.
Beyond active site competition, anthocyanins induce significant conformational changes in enzyme secondary structures. Circular dichroism analysis showed progressive reduction in α-helix content in α-amylase from 34.08% (control) to 21.35% at 0.5 mg/mL anthocyanin, while β-sheet content rose from 16.45% to 31.06%. In glucosidase, α-helix decreased from 34.08% to 22.39%, β-sheet increased from 16.45% to 29.06%, and random coil content also rose. These shifts suggest partial unfolding or destabilization of the tertiary structure, impairing catalytic efficiency. Such conformational disruptions likely result from non-covalent interactions between anthocyanins and amino acid side chains, altering the enzyme’s flexibility and substrate recognition capacity.
The dual action—competitive inhibition at the active site and global structural destabilization—explains the observed suppression of enzyme activity.CCDC22 Antibody medchemexpress By occupying the catalytic center and modifying the protein fold, anthocyanins effectively render the enzymes less efficient even when substrates are present.PMID:34257392 This mechanism is consistent with previous reports on polyphenol-protein interactions, where flavonoids alter enzyme dynamics through allosteric or direct binding effects.
These findings highlight the potential of anthocyanins as natural modulators of carbohydrate digestion. Their ability to simultaneously target multiple aspects of enzyme function makes them promising candidates for functional food development aimed at reducing postprandial hyperglycemia. Future research should focus on isolating specific anthocyanin derivatives with optimal inhibitory profiles and evaluating their bioavailability and metabolic fate in vivo. Additionally, comparative studies across different starch sources could reveal context-dependent effects, further refining their application in diabetic nutrition strategies.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com