Antibacterial Effectiveness of 96% Ethanolic Extract of Phaleria macrocarpa Leaves Against Bacillus cereus In Vitro

Abstract

Background: Foodborne poisoning due to Bacillus cereus contamination remains a serious public health concern, and mahkota dewa (Phaleria macrocarpa) leaves contain bioactive compounds (flavonoids, saponins, quinones, and steroids) with potential antibacterial activity. Objectives: This study aimed to evaluate the in vitro antibacterial effectiveness of a 96% ethanolic leaf extract of P. macrocarpa against B. cereus and to compare its activity with erythromycin. Material and Methods: A laboratory experimental study with a post-test-only control group design was conducted using the agar well diffusion method. The extract was tested at 12.5%, 25%, 50%, 75%, and 100% against B. cereus ATCC 11778; erythromycin (15 µg) served as the positive control and 10% DMSO as the negative control. All treatments were performed in quadruplicate, inhibition zones were measured, and data were analyzed using one-way ANOVA followed by Tukey’s HSD test. Results: Phytochemical screening indicated the presence of flavonoids, saponins, quinones, and steroids. The extract produced mean inhibition zones of 2.19 ± 0.55 mm and 4.94 ± 0.83 mm at 12.5% and 25% (weak), 5.88 ± 0.48 mm and 8.13 ± 0.48 mm at 50% and 75% (moderate), and 11.06 ± 0.43 mm at 100% (strong), whereas erythromycin produced a 23.96 ± 1.19 mm inhibition zone; significant differences were observed among groups (F = 475.607; p < 0.001). Conclusions: The 96% ethanolic leaf extract of P. macrocarpa exhibits dose-dependent antibacterial activity against B. cereus, with the 100% concentration showing the highest effect, although its activity remains lower than erythromycin.