<![CDATA[Infections caused by Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa remain a major public health burden, and the growing prevalence of antibiotic resistance has driven the search for natural antibacterial alternatives. Sunkist orange (Citrus sinensis) peel, an abundant agro-industrial waste, contains bioactive compounds such as flavonoids, limonene, tannins, and essential oils with reported antibacterial potential. This study aimed to evaluate the antibacterial activity of ethanol extract of Sunkist orange peel against the three bacteria using the disc diffusion method. A true experimental laboratory design with a completely randomized post-test only control group design was applied. The extract was obtained through maceration with 96% ethanol and tested at concentrations of 25%, 50%, 75%, and 100%, with Ciprofloxacin as positive control and distilled water as negative control, each in triplicate. Inhibition zone diameters were analyzed descriptively and inferentially using Shapiro-Wilk, Levene's Test, Kruskal-Wallis, and Mann-Whitney U post hoc tests. Results showed that the extract produced inhibition zones at all concentrations, increasing in a dose-dependent manner. The highest mean inhibition was observed against E. coli (17.28 mm at 100%), followed by P. aeruginosa (10.73 mm) and S. aureus (9.92 mm). Kruskal-Wallis tests revealed significant differences among concentration groups for all three bacteria (p < 0.05), confirming a genuine concentration-dependent effect, although all extract concentrations remained significantly weaker than the positive control. These findings support the potential of Sunkist orange peel as a natural antibacterial agent, though further purification and phytochemical quantification are recommended.]]>
