In vitro activity
The isolates of yeasts tested in this study exhibited different
sensitivities against monoterpenes (Table 1). CIT was more
active against C. neoformans and T. asahii; however, CIT showed
lower MIC against Candida species than its isolated isomers.
The results of GOL and NOL against yeasts were not impressive,
especially for Candida species. It should be mentioned that all
yeast strains were susceptible to CIT in the concentration range
evaluated (0.25 – 128 μg.ml-1).
For dermatophyte isolates, the greatest effect of
monoterpenes was observed against T. rubrum (GMIC of 22.9
μg.ml-1). GOL and CIT were the most active monoterpenes
against Microsporum strains (GMIC of 19.5 and 23.8 μg.ml-1) and
highly effective against dermatophytes (GMIC of 25.4 and 16.0
μg.ml-1, respectively).
In general, the monoterpenes were more active against
dermatophytes than yeasts (Fig. 2). The GMIC of monoterpenes
were 34.5 and 100.4 μg.ml-1 for dermatophytes and yeasts,
respectively.
CIT was active against all strains of yeasts and
dermatophytes. GOL and GAL had intermediate activity,
similar to CIT in many strains. Furthermore, trans isomers (GOL
and GAL) showed greater activity than cis isomers (NOL and
GOL). The Mann-Whitney test showed a statistical difference
between MIC of trans and cis isomers (p = 0.007) with GMIC of
56.3 and 99.0 μg.ml-1, respectively.