# Inhibitory effects of carvacrol on glucansucrase from Streptococcus mutans and salivary α-amylase: in silico and in vitro studies

## TL;DR

Carvacrol, a natural compound, effectively inhibits an enzyme linked to tooth decay without significantly affecting a key digestive enzyme, suggesting it could be a safer alternative for preventing dental caries.

## Contribution

This study demonstrates that carvacrol selectively inhibits glucansucrase from Streptococcus mutans with stable binding, offering a more targeted approach than existing inhibitors.

## Key findings

- Carvacrol reduced glucansucrase activity by 51.25% at 50 mM and showed stable binding in molecular dynamics simulations.
- Carvacrol had minimal effect on salivary amylase at 10 mM, unlike acarbose, which inhibited both enzymes significantly.
- Molecular docking showed carvacrol formed hydrogen bonds with key residues in glucansucrase, indicating strong and stable interactions.

## Abstract

Streptococcus mutans produces glucansucrase, an enzyme that converts sucrose into lactic acid, which lowers the pH in the oral environment and leads to tooth enamel demineralization, a key factor in dental caries. Additionally, glucansucrase facilitates the formation of extracellular polysaccharides, which promote bacterial adhesion to tooth surfaces. This study investigates the inhibitory effects of carvacrol, a natural compound, on glucansucrase activity both in vitro and in silico.

Glucansucrase enzyme was purified from S. mutans. The inhibitory effects of carvacrol against glucansucrase enzyme were investigated both in vitro and in silico.

In the presence of 50 mM carvacrol, glucansucrase and salivary amylase activities were reduced by 51.25% and 14.85%, respectively. Carvacrol did not significantly inhibit (4.73%) the salivary amylase enzyme at 10 mM. Glucansucrase activity decreased by 51.63% in the presence of 10 mM acarbose, which was used as a positive control in glucansucrase enzyme studies. Acarbose inhibited salivary amylase with 82.54% loss of enzyme activity in the presence of 1 mM acarbose. The docking score obtained for carvacrol was −5.262 kcal/mol, while that obtained for acarbose was −6.084 kcal/mol. We carried out molecular dynamics simulation studies for 100 ns to determine the stability of carvacrol in the active site of the protein. Carvacrol demonstrated stable binding to glucansucrase with hydrogen bonds and interactions at key residues (ASP477, GLN960, and ASP909), confirmed by molecular dynamics simulations. Carvacrol remained stable between 16 and 100 ns.

Carvacrol selectively inhibits glucansucrase without significantly affecting salivary amylase, making it a more targeted inhibitor compared to acarbose, which inhibits both enzymes. Docking studies indicated that while carvacrol has a lower binding affinity than acarbose, its stable interaction with the enzyme suggests sustained inhibitory action. These findings highlight carvacrol as a promising natural compound for preventing dental caries, offering a more selective alternative to traditional inhibitors. Further in vivo studies are necessary to assess its therapeutic efficacy and safety in clinical applications for oral health.