Red dragon fruit extract as a natural disclosing agent with antioxidant, antibacterial, and antibiofilm properties against Streptococcus mutans

Abstract

Dental caries is a widespread health concern driven by poor oral hygiene and biofilm-forming bacteria Streptococcus mutans. While chemical disclosing agents effectively visualize dental plaque, their potential risks, such as mucosal irritation, highlight the need for safer, natural alternatives. Red dragon fruit (Hylocereus polyrhizus) contains bioactive compounds (betacyanin and phyllocactin) with antioxidant, antibacterial, and antibiofilm properties, making it a promising candidate. This study employed molecular docking, in vitro assays, and formulation development to evaluate its potential as a natural disclosing agent. Docking simulations assessed the binding of betanin and phyllocactin to S. mutans biofilm-associated proteins (SrtA and GbpC). The extract was prepared using 70% ethanol through maceration. Antioxidant activity was measured using the DPPH assay; antibacterial and antibiofilm effects were evaluated through disc diffusion, MIC, MBC, and biofilm inhibition tests. Molecular docking showed strong binding affinities (–8.8 to –12.2 kcal/mol). The extract demonstrated antioxidant activity (IC₅₀: 158.43 µg/mL), antibacterial activity at 1000 µg/mL with a 5.43 mm inhibition zone, and antibiofilm activity up to 91.57%. The chewable jelly formulation exhibited suitable physical characteristics, though limited colour intensity remains a key challenge. Red dragon fruit extract showed potential as a natural disclosing agent for caries prevention in children, supported by its bioactive properties and docking results. Further studies are recommended to enhance colour intensity and validate its efficacy through in vivo applications.