Background and Objectives: Teeth decay and plaque are complicated problems created by oral pathogens. Tecoma stans (L.) and Cassia javanica (L.) are two ornamental evergreen plants widely distributed in Egypt. These plants are traditionally used for oral hygienic purposes. This study aims to elucidate the volatile oil constituents obtained from the flowers of these plants and evaluate the antimicrobial activity of these volatile oils against specific oral pathogens in comparison to chlorhexidine. Materials and Methods: The flowers obtained from both plants were extracted by n-hexane. GC-MS spectrometry was used to identify the constituents. Minimum inhibitory concentrations (MICs) were measured using tetrazolium salt (2,3-bis[2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide) (XTT). Results: GC-MS analysis revealed the presence of 32 and 29 compounds, representing 100% of the volatile constituents of Tecoma stans and Cassia javanica, respectively. The GC-MS analysis showed more than 60% of the volatile oil constituents are represented in both plants with different proportions. Chlorhexidine exerted stronger activity than tested plants against all microorganisms. Cassia javanica flower extract was more active against all tested microorganisms than Tecoma stans. Of note was the effect on Streptococcus mutans, which was inhibited by 100% at 12.5 and 25 µg/mL of Cassia javanica and Tecoma stans, respectively. The growth of Lactobacillus acidophilus was also completely inhibited by 25 µg/mL of the Cassia javanica extract. MIC90 and MIC were also calculated, which revealed the superiority of Cassia javanica over Tecoma stans against all tested oral pathogens. Conclusion: Cassia javanica flower volatile oils showed a potential anti-oral pathogen activity at relatively low concentrations. Also, Cassia javanica and Tecoma stans demonstrated a strong activity against tooth decay's notorious bacteria Streptococcus mutans. Both plants can be potential substituents to chlorhexidine. Formulating the constituents of these plants in toothpastes and mouthwashes as anti-oral pathogen preparations can be an interesting future plan.
Keywords: Cassia javanica; Streptococcus mutans; Tecoma stans; antimicrobial activity; chlorhexidine; oral pathogens; volatile oils.