<![CDATA[Basil leaf extract is a promising botanical ingredient for antibacterial mouthwash development. This study formulated a mouthwash containing size-processed basil (Ocimum basilicum L.) leaf extract and evaluated its physicochemical characteristics and in vitro antibacterial activity against Streptococcus mutans and Escherichia coli. Dried leaf powder was macerated with 96% ethanol; the concentrated extract was subsequently homogenized and ultrasonicated, yielding a mean particle size of 424.9 nm before formulation. Mouthwashes containing 5%, 10%, and 15% w/v extract were assessed for organoleptic characteristics, pH, four-week visual stability, and antibacterial activity by disc diffusion (n = 3 per group). Mean inhibition-zone diameters for the 5%, 10%, and 15% formulations were 9.27, 11.63, and 16.33 mm against S. mutans and 9.77, 12.07, and 17.03 mm against E. coli, respectively. The extract-free vehicle produced no inhibition zone, whereas the commercial mouthwash comparator produced larger zones than the test formulations. Omnibus analyses identified differences among groups, and post-hoc analyses were used to characterize pairwise patterns. The 15% formulation produced the largest mean inhibition zones among the extract-containing mouthwashes and maintained its organoleptic characteristics during four weeks of observation. These findings support further formulation development, while longer-term stability, antibiofilm activity, and oral-mucosal safety require additional investigation.]]>
