Inhibition potential of the ethanol extract of grapefruit peel (Citrus maxima) on the growth of Streptococcus mutans causing dental caries in-vitro

Introduction: Caries is an infection that occurs in the hard tissue of teeth, caused mainly by Streptococcus mutans. The caries process can be inhibited mechanically, chemically, or both. A natural ingredient known to have antibacterial effects is grapefruit (Citrus maxima). It is unknown whether ethanol extract from grapefruit peel can inhibit the growth of Streptococcus mutans, which causes dental caries. This research aimed to determine the inhibitory power of ethanol extract from grapefruit peel (Citrus maxima) on the growth of Streptococcus mutans, which causes dental caries in vitro. Method: This research design was quasi-experimental; the number of samples was 30 from six treatments. Each treatment consisted of five bacterial culture samples added with 20%, 50%, and 75% ethanol extract of grapefruit peel, negative control, and positive control. A 100% grapefruit peel extract was diluted with distilled water to obtain concentrations of 25%, 50% and 75%. Each extract concentration, positive control (chlorhexidine 0.2%), and negative control (sterile water) were saturated on a blank disk for 1 hour at room temperature. The Streptococcus mutans bacterial suspension was spread on a petri dish containing Mueller Hinton Blood (MHB) agar media. Then, place each blank disc containing the saturated extract, positive control, and negative control on the petri dish. Next, incubation was carried out at 37oC for 24 hours. After the incubation time is complete, the clear zone formed around the blank disc is observed, and its diameter is measured using a caliper. Then, the results of the observation are recorded. ANOVA tests were used to evaluate differences among groups, all values were considered significant if p<0.05. Result: The results showed that the ethanol extract of grapefruit peel positively contained flavonoids of 102.92 ± 1.96 mg/100g QE, tannins of 6,867.61 ± 167.95 mg/100g TAE, phenols of 4,865.65 ± 106.83 mg/100g GAE. The results of the 25% concentration inhibition test were 6.7517. Meanwhile, 50% concentration is 7.2583, and 75% concentration is 7.7550 (difference among group ANOVA test p<0.05). Conclusion: The ethanol extract of grapefruit peel can inhibit the growth of Streptococcus mutans bacteria, which causes dental caries in vitro.