Antibacterial activity of Bixa orellana compared with Camellia sinensis against Streptococcus mutans: An in vitro comparative study

Aim: Bixa orellana and Camellia sinensis are plant species cultivated in several South American countries such as Peru and used to combat diseases due to their antimicrobial properties. The aim of this study was to assess the antibacterial activity of the methanolic extract of B. orellana compared with the ethanolic extract of C. sinensis against Streptococcus mutans at 24, 48, and 72 h. Materials and Methods: This in vitro and longitudinal experimental study had a sample of 12 wells per group. The antibacterial activity was assessed at concentrations of 1000 mg/mL (100%), 750 mg/mL (75%), and 500 mg/mL (50%), by the well diffusion method on Müller Hinton Agar in two stages. In first stage, antibacterial activity of ethanolic extract of C. sinensis and methanolic extract of B. orellana was determined. In second stage, concentrations of both extracts with higher antibacterial activity were compared using 0.12% chlorhexidine as a control. In addition, antibacterial sensitivity was assessed according to Duraffourd's scale and the minimum inhibitory and bactericidal concentration (MIC and MBC) was determined. Statistical analysis was performed using Kruskall Wallis test and ANOVA test of one factor inter-group and intra-group with Tukey and Bonferroni post hoc, considering a significance level of 5%. Results: In first stage, ethanolic extract of C. sinensis (100% and 75%) and methanolic extract of B. orellana (100% and 75%) showed higher antibacterial activity against S. mutans at 48 h (P 0.001 and P 0.05, respectively). In second stage, at 48 h, highly sensitive activity was observed against C. sinensis (100% and 75%) and B. orellana at 100%. In addition, C. sinensis at 100% and 75% showed significantly higher antibacterial activity against S. mutans compared with B. orellana (P 0.05) and chlorhexidine (P 0.05). Likewise, a significant increase in antibacterial activity could be observed in all concentrations at 48 h (P 0.001), decreasing significantly in all groups at 72 h (P 0.001). The MIC of the ethanolic extract of C. sinensis was 250 mg/mL and the MBC was 500 mg/mL. In the methanolic extract of B. orellana the MIC was 125 mg/mL and the MBC was 500 mg/mL. Conclusion: Ethanolic extract of C. sinensis and methanolic extract of B. orellana, both at 100% concentration, presented their highest antibacterial activity against S. mutans at 48 h, with C. sinensis more effective compared with B. orellana. However, this antibacterial effect decreased in both extracts at 72 h. The MBC of C. sinensis and B. orellana against S. mutans was 500 mg/mL for both extracts, whereas the MIC was 250 mg/mL and 125 mg/mL, respectively, for both extracts.