Violacein: a natural antibacterial agent empowered by film-forming sprays for topical applications

OBJECTIVE: The rise of antibiotic-resistant microorganisms poses a significant public health threat. Exploring natural compounds with antibacterial properties offers a potential solution. Violacein, derived from Chromobacterium violaceum, has shown promise for its antibacterial and antioxidant effects. This study aims to develop and evaluate a violacein-loaded film-forming spray (FFS) to enhance patient adherence through a flexible, peelable skin film, while maintaining antibacterial efficacy. METHODS: The antibacterial and antioxidant activities of violacein crude extract were evaluated. Then a central composite design was employed to optimize the FFS formulation by varying the concentration of the film-forming agent (Eudragit® RS 100), solvent ratio (ethanol), and diethyl phthalate (plasticizer). The properties of both liquid and film forms were characterized. RESULTS: Violacein exhibits both antibacterial and antioxidant effects. Altering the concentration of Eudragit® RS 100 and the ethanol-to-water ratio impacts viscosity, drying time, and toughness, affecting the spray radius. Increasing diethyl phthalate concentration reduces stress (the force the film can withstand before deformation) and Young’s modulus (a measure of stiffness) but increases strain (the film’s ability to stretch before breaking). The optimized formulation consists of 17.41%w/w Eudragit® RS 100, 20%w/w diethyl phthalate (DEP), and a 4:1 (w/w) ethanol-to-water ratio, producing a flexible, durable film with a wide spray radius and viscosity ranging from 0.025 to 0.045 Pa·S. Importantly, the violacein-loaded FFS exhibits superior antibacterial activity compared to a commercial clindamycin solution. CONCLUSION: The developed violacein-loaded FFS successfully generated a flexible and durable film, with significant in vitro antibacterial activity. This evidence suggests its potential for further development as an effective topical formulation that may enhance patient adherence.