<![CDATA[Introduction: Durian peel is a source of phytochemicals with antibacterial potential, and particle-size reduction may modify dispersion and measured in vitro activity. This study evaluated the operational minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of ethanol extract and a size-reduced ("nano extract") preparation of durian peel against Staphylococcus epidermidis. Methods: The ethanol extract was prepared by maceration with 96% ethanol; 30 g of the same extract was homogenized at 1,700 rpm for 1 h and ultrasonicated for 1 h. Particle size, phytochemical screening, broth absorbance at 600 nm, qualitative subculture, and disk diffusion were evaluated in triplicate (n=3). Inhibition-zone data were analyzed using one-way ANOVA. Results: The mean particle size was 645.72 nm. Operational MIC values were 6.25% for the ethanol extract and 0.625% for the nano extract, while no growth after subculture was observed at 50% and 5%, respectively. Mean inhibition zones ranged from 6.6-14.5 mm and 8.3-18.3 mm, with significant concentration-related differences within each series (p<0.001). Discussion and conclusion: The size-reduced preparation reached inhibitory endpoints at lower nominal concentrations within its test series. However, final concentrations were not analytically verified, and optical interference and qualitative bactericidal endpoints limit direct inference of intrinsic potency. These findings support in vitro antibacterial activity but do not establish a quantified increase in potency or a reduction in therapeutic dose]]>
