Antibacterial activity of Bixa orellana L. (achiote) against Streptococcus mutans and Streptococcus sanguinis

Objective To evaluate the cytotoxic and antibacterial effect of Bixa orellana L. ( B. orellana ) (achiote) methanol extract against Streptococcus mutans (ATCC 25175) ( S. mutans ) and Streptococcus sanguinis (ATCC 10556) ( S. sanguinis ). Methods Two methanol extracts of B. orellana were prepared in vitro , from the seeds and leaves. The antibacterial activity of extracts against S. mutans and S. sanguinis was evaluated using the cup-plate agar diffusion method. The minimum inhibitory concentration (MIC) was determined using the microdilution method and the cytotoxic activity was determinated by using the cell line MDCK. Results A stronger antibacterial effect was observed with the leaves methanolic extract with an inhibition zone of (19.97 ± 1.31) mm against S. mutans and (19.97 ± 1.26) mm against S. sanguinis . The methanolic extract of the seeds had an activity of (15.11 ± 1.03) mm and (16.15 ± 2.15) mm against S. mutans and S. sanguinis , respectively. The MIC of the leaf and the seed extracts against S. sanguinis was 62.5 and 125 μg/mL, respectively, and the MIC of the leaf extract against S. mutans was 62.5 μg/mL, and for the seed extract it was 31.25 μg/mL. The 50% cytotoxic concentration was 366.45 and 325.05 μg/mL for the leaves and seeds extracts, respectively. Conclusions The experimental findings demonstrated the antibacterial effect of the methanolic extract of B. orellana (achiote) on S. mutans and S. sanguinis . The extract of this plant is cytotoxic at high concentrations.