Antimicrobial Activity of the Essential Oil ofPlectranthus neochilusagainst Cariogenic Bacteria

Abstract

This work used the broth microdilution method to investigate the antimicrobial activity of the essential oil obtained from the leaves ofPlectranthus neochilus(PN-EO) against a representative panel of oral pathogens. We assessed the antimicrobial activity of this oil in terms of the minimum inhibitory concentration (MIC). PN-EO displayed moderate activity againstEnterococcus faecalis(MIC = 250 μg/mL) andStreptococcus salivarus(MIC = 250 μg/mL), significant activity againstStreptococcus sobrinus(MIC = 62.5 μg/mL),Streptococcus sanguinis(MIC = 62.5 μg/mL),Streptococcus mitis(MIC = 31.25 μg/mL), andLactobacillus casei(MIC = 31.25 μg/mL), and interesting activity againstStreptococcus mutans(MIC = 3.9 μg/mL). GC-FID and GC-MS helped to identify thirty-one compounds in PN-EO;α-pinene (1, 14.1%),β-pinene (2, 7.1%),trans-caryophyllene (3, 29.8%), and caryophyllene oxide (4, 12.8%) were the major chemical constituents of this essential oil. When tested alone, compounds1,2,3, and4were inactive (MIC > 4000 μg/mL) against all the microorganisms. These results suggested that the essential oil extracted from the leaves ofPlectranthus neochilusdisplays promising activity against most of the evaluated cariogenic bacteria, especiallyS. mutans.