Suha M Abudoleh¹ , Nisreen A Dahshan², Zead Abudayeh², Dima N Lafi², Ahmad A Talhouni³, Juhaina M Abu Ershaid², Amjad Abuirmeileh⁴

Abstract

Purpose: To evaluate the phytochemical composition and antibacterial potential of Delonix regia (Royal Poinciana) flowers and leaves. Methods: Flowers and leaves extract of Delonix regia was prepared using the Soxhlet apparatus. The phytochemical composition of plant extract was evaluated using High-Performance Liquid Chromatography (HPLC)/Mass Spectrometry. The Agar well diffusion method, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) were used to test the antibacterial activity of the plant extract. Microtiter plate method was used to study the effect of extract on Pseudomonas aeruginosa biofilm. Results: Extraction yields were highest in methanol (≈ 35 %), suggesting a higher concentration of polar bioactive constituents. The HPLC-MS analysis identified diverse compounds, including phenolic acids, flavonoids, terpenoids, sterols, and carotenoids, with rutin, β-sitosterol, and lupeol as major constituents of the methanolic flower extract. Among all extracts, methanolic flower extract exhibited the broadest antibacterial spectrum. The extract significantly reduced P. aeruginosa biofilm formation by over 80 % at concentrations ≥ 25 mg/mL. Scanning electron microscopy confirmed marked biofilm disruption and bacterial morphological alterations. Conclusion: These results suggest that D. regia methanolic flower extract harbors potent bioactive compounds capable of inhibiting both planktonic growth and biofilm formation of pathogenic bacteria. Although the active concentrations appear high for systemic use, they are fully appropriate for topical wound applications and antimicrobial coatings, where higher local doses are acceptable.