Ultrastructural studies of bacterial cells treated with carvacrol
and eucalyptol have suggested that the oxygenated groups present
in eucalyptol disturb the bacterial membrane structures, even
when eucalyptol is present in the growth media at subinhibitory
concentrations; therefore, eucalyptol could allow carvacrol to be
more easily transported into the bacterial cells, where it can
interact with different intracellular targets (de Sousa et al., 2013;
Sousa et al., 2015). Overall, the presence of eucalyptol in the
growth media was found to decrease the required amount of
carvacrol needed to promote antimicrobial effects. Carvacrol is a
thymol-isomer presenting structural differences due to the position
of its hydroxyl group (OH group); however, carvacrol and thymol
have similar mechanisms of action against bacterial cells