Anti-quorum sensing and biofilm-disrupting properties of Hibiscus sabdariffa calyx extract against Staphylococcus aureus

Flavonoid- and anthocyanin-rich plant extracts are gaining attention as natural alternatives to conventional antibiotics due to the increasing prevalence of antibiotic-resistant bacteria. This prompted the study to determine the drug potential of Hibiscus sabdariffa calyx crude ethanolic extract (in 5%, 15%, and 30% concentration) against Staphylococcus aureus ATCC 25923—which are Gram-positive biofilm-forming bacteria known for its wide range of implications, from superficial skin infections to life-threatening systemic diseases. The study employed a triplicate, mixed-methods experimental design, and visual observations of the disruption, alteration, or fragmentation of structures in untreated biofilms and in response to different extract concentrations. Qualitative phytochemical analysis confirmed that the red calyces of H. sabdariffa contained various phytochemicals, including but not limited to flavonoids and anthocyanins. The biofilm inhibition was clear from the different concentrations of the extract, and both the Minimum Inhibitory Concentration (MIC) and Minimum Biofilm Inhibitory Concentration (MBIC) were determined. The statistical approach through one-way ANOVA and Tukey’s HSD elucidated the observed differences among the groups are not due to random chance. The extent to which the extract was able to cause morphological changes in the biofilm were visualized through scanning electron microscopy (SEM) in 500x, 2000x, and 10000x magnification. The study implied that the extract has significant anti-quorum sensing and biofilm-disrupting properties in a concentration-dependent manner—30% having the highest zone of inhibition and approximately 0 meanOD of biofilm formation—although its immediate antibacterial action may be less potent or slower in onset than 30 μg Vancomycin when tested in Disk Diffusion.