Formulation and in Vitro Evaluation of a Spilanthes Acmella Herbal Mouthrinse against Streptococcus Mutans

Abstract

This investigation aimed to develop a herbal mouthrinse incorporating an ethanolic extract of Spilanthes acmella and to characterise its physicochemical attributes alongside its in vitro inhibitory activity against Streptococcus mutans. A herbal mouthrinse was compounded using a standardised S. acmella ethanolic extract as the active component within a proprietary hydroalcoholic vehicle system incorporating pharmaceutical excipients. A comprehensive physicochemical evaluation was conducted covering pH, viscosity, surface tension, organoleptic characteristics, salivary compatibility, and microbiological safety. Inhibitory activity against S. mutans (MTCC, Chandigarh) was evaluated through disc diffusion assay at volumes of 50, 100, 150, and 200 µl, with 0.2% chlorhexidine gluconate as the reference standard. The mouthrinse displayed a pH of 6.0, a viscosity of 2.1 ± 0.1 cP, and a surface tension of 35.2 ± 1.5 dynes/cm. Organoleptic assessment yielded a clear, pale-green, uniform preparation with a refreshing menthol character and a patient acceptability rating of 4.5/5. Microbiological testing confirmed safety with a total viable count of 12 CFU/mL and no pathogenic growth. Disc diffusion assay revealed concentration-dependent inhibition against S. mutans, with zones of inhibition ranging from 2.75 ± 0.19 mm at 50 µl to 11.44 ± 0.80 mm at 200 µl, versus 14.72 ± 1.03 mm for the chlorhexidine control. The S. acmella herbal mouthrinse exhibited clinically acceptable physicochemical properties, adequate microbiological safety, and meaningful concentration-dependent inhibitory activity against S. mutans, supporting its potential as a plant-derived adjunct to conventional dental hygiene strategies