<![CDATA[The utilization of natural materials as sources of antibacterial agents has been increasingly developed, including pineapple peel (Ananas comosus (L.) Merr.), which is known to be rich in natural bioactive compounds that may inhibit bacterial growth. This experimental study aimed to develop a gel soap formulation containing pineapple peel extract and to evaluate its physical quality and antibacterial activity against Staphylococcus aureus. Four formulations containing different concentrations of pineapple peel extract were tested, namely 0%, 0.5%, 1%, and 1.5%, designated as F0, F1, F2, and F3, respectively. Antibacterial activity was evaluated using the agar well diffusion method in triplicate. Inhibition zone diameter data were analyzed using the Shapiro–Wilk test, Levene’s test, one-way ANOVA, followed by Tukey’s HSD post-hoc test. The formulations were evaluated on days 1, 7, 14, 21, and 28 for organoleptic properties, homogeneity, pH, viscosity, spreadability, and foam stability. The results showed that all formulations were semisolid and homogeneous, with colors ranging from clear to deep yellow and a characteristic pineapple aroma. The pH values ranged from 5.49 to 7.04, viscosity from 8,230.00 to 15,606.67 cPs, spreadability from 4.17 to 6.40 cm, and foam stability from 64.40% to 87.73%. The antibacterial activity test demonstrated that all formulations exhibited strong inhibitory activity against Staphylococcus aureus, with mean inhibition zone diameters of 14.6 ± 0.15 mm for K+, 15.8 ± 0.40 mm for F0, 16.2 ± 0.55 mm for F1, 16.7 ± 0.25 mm for F2, and 17.3 ± 0.15 mm for F3. One-way ANOVA showed a statistically significant difference among the groups (p < 0.05). Based on these findings, pineapple peel extract gel soap demonstrated stable physical characteristics and antibacterial activity against Staphylococcus aureus, with the highest activity observed in the formulation containing 1.5% extract. However, the observed antibacterial activity cannot be attributed entirely to the pineapple peel extract because the base formulation also contained sodium lauryl sulfate (SLS), which may contribute to the antibacterial effect. These findings may serve as a basis for the further development of pineapple peel-based gel soap formulations, although further studies are required to determine the specific contribution of the extract to the observed antibacterial activity.]]>
