Table I Growth Inhibition Zone (mm) ± SD for Limonene and Its Isomerization/Dehydroaromatization Products by Disk Diffusion Method Organisms Substances Natural limonene Reaction mixture after isomerization p γ Limonene (template) Terpinolene α-Terpinene E. coli 9.0 ± 0.1 21.0 ± 0.2 0.0 ± 0.0 0.0 ± 0.0 0.0 ± 0.0 21.3 ± 0.1 9.2 ± 0.0 S. epidermidis 9.1 ± 0.1 24.1 ± 0.3 8.3 ± 0.2 0.0 ± 0.0 10.3 ± 0.2 18.4 ± 0.4 18.5 ± 0.1 C. albicans 25.2 ± 0.2 33.3 ± 0.3 0.0 ± 0.0 0.0 ± 0.0 13.1 ± 0.3 20.1 ± 0.7 20.2 ± 0.4 T. rubrum 9.0 ± 1.0 90.0 ± 2.0 0.0 ± 0.0 42.0 ± 1.5 10.2 ± 0.0 25.2 ± 0.9 27.2 ± 0.7 T. viride 12.0 ± 0.1 21.1 ± 0.2 0.0 ± 0.0 0.0 ± 0.0 14.2 ± 0.3 42.2 ± 1.0 14.2 ± 0.2 A. niger 0.0 ± 0.0 24.1 ± 0.3 8.1 ± 0.2 0.0 ± 0.0 13.3 ± 0.8 32.3 ± 1.0 0.0 ± 0.0 P. commune 0.0 ± 0.0 33.3 ± 0.3 0.0 ± 0.0 0.0 ± 0.0 0.0 ± 0.0 22.3 ± 0.0 0.0 ± 0.0 C. cladosporioides 33.4 ± 0.3 90.0 ± 2.0 0.0 ± 0.0 0.0 ± 0.0 16.0 ± 0.5 52.2 ± 1.0 14.2 ± 0.0 A. alternata 0.0 ± 0.0 51.5 ± 1.4 0.0 ± 0.0 0.0 ± 0.0 12.0 ± 0.0 23.2 ± 0.0 10.1 ± 0.0 ANTIMICROBIAL PROPERTIES OF NATURAL LIMONENE 143

JOURNAL OF COSMETIC SCIENCE 144 tested in the study (including T. rubrum) was highly promising. For example, T. rubrum is the most common species that causes extremely diffi cult to cure (due to resistance to most of the commercially available antifungal agents) foot and nail infections (26). Moreover, terpinolene was found to be a very active antifungal agent against A. niger. The fungus Aspergillus has become a growing concern in the past few years as a causative agent of Figure 3. Trichophyton rubrum growth inhibition zones around disks impregnated with tested compounds.