Phytochemical Assessment, Evaluation of Antioxidant and Antibacterial Properties, and Molecular Docking to Elucidate the Regulation of Bacterial Biofilm Formation in an Herbal Formulation for the Treatment of Abscesses

Abscess formation is commonly precipitated by bacterial infection. This study delineates the phytochemical composition and evaluates the antioxidant, antibacterial, and anti-biofilm activities of a Thai traditional anti-abscess herbal formulation comprising Curcuma zedoaria, Vitex trifolia, and Azadirachta indica. Validated high-performance liquid chromatography–photodiode array detection (HPLC–PDA) analysis of the ethanolic extract identified curcumin, demethoxycurcumin, bisdemethoxycurcumin, and vitexicarpin as principal constituents. Total phenolic and flavonoid contents were 32.08 ± 2.54 mg GAE/g and 17.52 ± 1.28 mg QE/g dry weight, respectively. Antioxidant assessment by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay yielded an half maximal inhibitory concentration (IC50) of 53.46 ± 3.24 µg/mL, while reducing power corresponded to 383.97 ± 13.24 µg FeSO4/g dry weight. Molecular orbital analysis revealed a highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO–LUMO) gap for vitexicarpin (ΔE = 9.7710 eV), indicative of greater radical-scavenging potential relative to curcuminoids. Antibacterial assays demonstrated selective activity against Staphylococcus epidermidis (inhibition zone 1.48 ± 0.16 cm), with no observed inhibition of Staphylococcus aureus or Streptococcus pyogenes. Curcumin exhibited the highest activity against S. epidermidis (minimum inhibitory concentration (MIC) 62.5 µg/mL; minimal bactericidal concentration minimal bactericidal concentration (MBC) 125 µg/mL). Molecular docking showed curcumin binding to the teicoplanin-associated transcriptional regulator (TcaR) with a binding energy of −8.00 kcal/mol, comparable to methicillin (−8.16 kcal/mol), suggesting a potential mechanism for modulation of biofilm-associated regulatory pathways. Collectively, these findings indicate that the formulation has measurable antioxidant activity and targeted antibacterial efficacy against S. epidermidis, which may contribute to attenuation of abscess progression via interference with biofilm regulation.