Antifungal activity of geraniol and citronellol, two monoterpenes alcohols, against Trichophyton rubrum involves inhibition of ergosterol biosynthesis

Figures & data

Table 1. MIC values (µg/mL) of geraniol and citronellol against Trichophyton rubrum strains by microdilution method.

	Strains
Drugs^a	ATCC 1683	LM 98	LM 130	LM 222	LM 309	LM 333	LM 422	LM 582	LM 600	LM 640	LM 710	LM 713	LM 720	LM 722
Geraniol	32	64	64	64	16	32	32	16	32	256	16	16	64	64
Citronellol	128	128	64	32	32	8	128	64	32	128	256	32	1024	128

^aThe results are expressed as geometric mean of three experiments.

Figure 1. Percentage of dry mycelial weight produced by Trichophyton rubrum in the absence (control) and presence of geraniol (MIC: 32 g/mL; 2 × MIC: 64 g/mL) and citronellol (MIC: 128 g/mL; 2 × MIC: 256 g/mL). (a) T. rubrum ATCC 1683; (b) T. rubrum LM 422. Control produced 100% of dry mycelial weight. *p < 0.05 compared with control.

Figure 2. Percentage of germinated conidia of Trichophyton rubrum ATCC 1683 (a) and LM 422 (b) in the absence (control) and presence of geraniol (MIC: 32 g/mL; 2 × MIC: 64 g/mL) and citronellol (MIC: 128 g/mL; 2 × MIC: 256 g/mL). *p < 0.05 compared with control.

Figure 3. Rate of release of intracellular material from Trichophyton rubrum ATCC 1683 absorbing at 260 nm in the absence (control) and presence of geraniol (MIC: 32 µg/mL; 2 × MIC: 64 µg/mL) and citronellol (MIC: 128 µg/mL; 2 × MIC: 256 µg/mL). Lysing agent induced 100% of release of intracellular material. *p < 0.05 compared with control.

Table 2. Observations detected in microculture of Trichophyton rubrum in the absence (control) and presence of geraniol and citronellol (MIC/2).

Observations	Control	Geraniol	Citronellol
Conidiogenesis	^+++	^+	^+
Normal arrangement of conidia	^+++	^+++	^−
Macroconidia	^−	^−	^−
Chlamydoconidia	^−	^+	^−
Wide hyphae	^−	^++	^+
Short and winding hyphae	^−	^++	^+

⁺⁺⁺Strong, ⁺⁺intermediate, ⁺low, and ⁻absent.

Table 3. MIC values (µg/mL) of geraniol and citronellol in the absence and presence of sorbitol (0.8 M) against Trichophyton rubrum ATCC 1683.

Drugs	− Sorbitol^a	+Sorbitol^a	Control
Geraniol	32	2048	+
Citronellol	128	4096	+

^aThe results are expressed as a geometric mean of three experiments. ⁺Fungal growth in the presence of sorbitol (0.8 M) and absence of drugs.

Figure 4. Ergosterol content as a percentage of the wet weight of the Trichophyton rubrum ATCC 1683 cell in the absence (control) and presence of geraniol (MIC: 32 µg/mL; 2 × MIC: 64 µg/mL), citronellol (MIC: 128 µg/mL; 2 × MIC: 256 µg/mL) and ketoconazole (MIC: 16 µg/mL; 2 × MIC: 32 µg/mL). *p < 0.05 compared with control.