Phytochemical Analysis and Antibacterial Activity of Stevia Rebaudiana Bertoni Leaves Extract against Streptococcus sanguis (A Primary Inhabitant of Dental Plaque): In Vitro Study

Objective: Dental plaque is considered the primary causative agent in developing periodontal diseases. Early colonizers of dental plaque, such as Streptococcus sanguis (S.sanguis), are crucial in the succession steps of biofilm formation. As an alternative to the commonly used chlorohexidine (CHX), it is of interest to find naturally occurring antimicrobial substances from plants. Materials and Methods: Volunteers were asked to provide plaque samples. Microscopic examination, gram stain, optochin test, catalase test and polymerase chain reaction were used to ensure the identification of S. sanguis. Stevia Rebaudiana Bertoni leaves extracted by 70% ethanol alcohol. Four experiments have been done in this study: the susceptibility of S. sanguis to stevia extract, the minimum inhibitory (MIC) and the minimum bactericidal (MBC) concentrations, and exploration of the extract effective constituents by using HPLC. Results: Stevia extract had good antibacterial activity with varying inhibition zone diameters that were concentration dependent, but 0.2% CHX showed better activity with a statistically significant difference (p < 0.05). Both MIC and MBC were at 16 mg/ml. HPLC analysis confirmed the presence of antibacterial constituents: narigenin 25.76 ppm, catechin 30.25 ppm, coumarin 25.47 ppm, and kaempferol 4.59 ppm. Conclusions: The antimicrobial activity of the alcoholic Stevia Rebaudiana Bertoni leaf extract was satisfactory. The study extract exhibited lower antibacterial activity at 512 mg/ml of stevia extract, while 0.2% CHX had superior activity overall. HPLC showed that the alcoholic leaves extract of Stevia Rebaudiana Bertoni contains several active antibacterial components: narigenin, catechin, coumarin and kaempferol.