Antibacterial Property of Synsepalum dulcificum Leaves Aqueous Extract against Oral Pathogens and its Chemical Compounds

Synsepalum dulcificum (S. dulcificum) commonly known as “miracle fruit” because its berries have the capability to modify sour taste to the sweet taste when eaten. Beside the berries, S. dulcificum leaves were also known to possess biological properties such as antioxidant, antimutagenic and antidiabetic activities. However, the study of its antimicrobial activity against oral pathogen is still lacking. Thus, this study aimed to evaluate the antibacterial activity of its leaves against cariogenic bacteria and to analyse its phytochemical compounds. The samples of S. dulcificum leaves were collected in Kelantan, the east coast region of Peninsular Malaysia and extracted with distilled water using a Soxhlet technique. The antibacterial activity of the S. dulcificum leaves aqueous extract against Streptococcus mutans (S. mutans), Streptococcus sobrinus (S. sobrinus) and Lactobacillus salivarius (L. salivarius) was evaluated using the broth microdilution assay. The identification of the phytochemical compounds was performed using gas chromatography-mass spectrometry (GC-MS). The antibacterial study showed the minimum inhibitory concentration of S. dulcificum leaves aqueous extract against S. mutans and S. sobrinus were 16 mg/mL and 8 mg/mL, respectively. Interestingly, there was no inhibitory effect of S. dulcificum leaves aqueous extract against L. salivarius. A total of 42 chemical compounds were identified and major identified bioactive compounds groups were heterocyclic and phenolic compounds. Our results suggested S. dulcificum leaves aqueous extract has antimicrobial properties against S. mutans and S. sobrinus, but no inhibitory activity against oral normal flora, with the presence of bioactive compounds has potential in oral care products application.