Herbal Oral Gel Containing Cassia fistula and Rosa x damascena: A Natural Remedy with Anti-microbial Activity Against Recurrent Aphthous Stomatitis

Background: Recurrent aphthous stomatitis (RAS) is an ulcerative disease with unclear etiopathogenesis. Microbial agents are suggested as one of the predisposing factors. Cassia fistula and Rosa x damascena are two plant species with antimicrobial properties that are widely used for medicinal purposes. Objectives: The aim of the present study was to formulate and evaluate the antimicrobial activity of an oral gel consisting of C. fistula extract (Ex) and R. x damascena essential oil (EO) for the treatment of RAS. Methods: Cassia fistula Ex was prepared by the maceration method, and then the phenolic content was measured using the Folin-Ciocalteu reagent. The hydrodistillation method was used to prepare R. x damascena EO, and its ingredients were analyzed by gas chromatography-mass spectrometry (GC/MS). The antimicrobial activity of Ex, EO, Ex/EO, and the gel formulation was evaluated using disk diffusion and microbroth dilution methods against three strains: Streptococcus mutans, Actinomyces viscosus, and Candida albicans. Carbomer 940, carboxymethyl cellulose, and hydroxypropyl methyl cellulose polymers were combined with Ex/EO, and then the physicochemical parameters were checked. Results: Extract, EO, Ex/EO, and gel formulations each showed the highest and lowest inhibitory effect against C. albicans and A. viscosus, respectively. The antimicrobial potential of Ex and EO was dose-dependent, but no statistically significant difference was observed between two concentrations of 1.9 - 1.7% in Ex and 0.7 - 0.9% in EO (P < 0.05). The highest antimicrobial capacity belonged to the combination of 1.7% and 0.7% concentrations of Ex and EO. Carbomer 940 in combination with Ex/EO (1.7/0.7%) was identified as the optimal formulation. Conclusions: The Carbomer 940 gel formulation, with a uniform appearance without bubbles or lumps, a pH equal to 6.87 ± 0.04, good viscosity, an expiration date of 65 days, and acceptable antimicrobial activity, was considered the approved formulation in this study.