Thus, some essential oils used as antiinflammatory remedies suppress neutrophil activation by TNF-alpha at a low concentration (0.0125-0.025 %) in vitro.

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BACKGROUND: In aromatherapy, essential oils are used as anti-inflammatory remedies, but experimental studies on their action mechanisms are very limited. AIMS OF THE STUDY: To assess their anti-inflammatory activities, the effects of essential oils on neutrophil recruitment in mice were examined in vivo. METHOD: The effect of essential oils on leukocyte and neutrophil recruitment induced 6 h after intraperitoneal injection of casein in mice was examined. RESULTS: Leukocyte recruitment into the peritoneal cavity in mice was suppressed by intraperitoneal injections of geranium, lemongrass and spearmint oils at the dose of 5 microl/mouse, but was not by tea tree oil. This recruitment was inhibited dose-dependently by geranium oil. The suppression of leukocyte recruitment resulted from inhibition of neutrophil accumulation. CONCLUSION: Some essential oils used as anti-inflammatory remedies suppress neutrophil recruitment into the peritoneal cavity in mice.

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The therapeutic efficacy of tea tree oil (TTO), Melaleuca alternifolia, and its main component, terpinen-4-ol, were evaluated in a murine oral candidiasis model. Prednisolone -pretreated mice were orally infected with a fluconazole-susceptible (TIMM 2640) or a resistant (TIMM 3163) strain of Candida albicans to induce oral candidiasis. TTO or terpinen-4-ol was administrated with a cotton swab 3 h and 24 h after candida infection. These treatments clearly showed a decrease in the symptom score of tongues and in the viable candida cell number in the oral cavity at 2 d after azole-susceptible C. albicans infection, although the degree of the efficacy was less than that of fluconazole. Even against oral candidiasis caused by azole-resistant C. albicans, TTO and terpinen-4-ol were similarly effective, while fluconazole appeared ineffective. These results suggest that TTO and terpinen-4-ol may have the potential of therapeutic ability for mucosal candidiasis which may also be applicable to C. albicans oral candidiasis induced by the azole-resistant strain.

The onset of oral candidiasis is accompanied by inflammatory symptoms such as pain in the tongue, edema or tissue damage and lowers the quality of life (QOL) of the patient. In a murine oral candidiasis model, the effects were studied of terpinen-4-ol (T-4-ol), one of the main constituents of tea tree oil, Melaleuca alternifolia, on inflammatory reactions. When immunosuppressed mice were orally infected with Candida albicans, their tongues showed inflammatory symptoms within 24 h after the infection, which was monitored by an increase of myeloperoxidase activity and macrophage inflammatory protein-2 in their tongue homogenates. Oral treatment with 50 µL of 40 mg/mL terpinen-4-ol 3h after the Candida infection clearly suppressed the increase of these inflammatory parameters. In vitro analysis of the effects of terpinen-4-ol on cytokine secretion of macrophages indicated that 800 µg/mL of this substance significantly inhibited the cytokine production of the macrophages cultured in the presence of heat-killed C. albicans cells. Based on these findings, the role of the anti-inflammatory action of T-4-ol in its therapeutic activity against oral candidiasis was discussed.

By the combined use of agar diffusion, agar vapor and agar vapor-inhibitory assays, contribution of the vapor activity of essential oils was quantitatively estimated. The test organisms were Trichophyton mentagrophytes and Aspergillus fumigatus. Agar vapor assay was used to confirm the vapor activity of the oils. The parameter delta defined as a contribution index of the vapor activity was calculated by ( 1 b-c/a-c) 100, where a is inhibitory diameter in the diffusion assay, b is inhibitory diameter in the vapor-inhibitory assay and c is diameter of the sealed ring in the vaporinhibitory assay (21 mm). Many of the essential oils examined showed a delta value near 100, thus providing the major contribution of the vapor activity to the inhibitory diameter. Essential oils containing aldehyde as major constituent showed low delta value, indicating the major inhibition was due to agar diffusion. Major essential oil components behaved similarly; the delta value was increased in the following order: aldehyde phenol alcohol ester, oxide, hydrocarbon, indicating the enhanced contribution of the vapor activity in that order.

Farnesol is known as a quorum-sensing molecule for Candida albicans and is recognized to play pathogenic roles in Candida infection. To assess the possible role of farnesol in mucosal C. albicans infection, the effects of farnesol treatment against experimental oral candidiasis in mice were examined. Prednisolone-pretreated ICR mice were orally infected with C. albicans and 3, 24 and 30 hr later the animals were orally given farnesol. Forty-eight hr later they were killed for observation. Farnesol treatment in a dose ranging between 1.125 and 9 μmol/mouse showed a protective effect against oral candidiasis in a dose-dependent manner, at least as estimated by symptom scores of tongues. At 9 μmol/mouse it decreased bodyweight loss. Histological studies of 2.25 μmol/mouse farnesol-treated animals indicated that farnesol suppressed mycelial growth of C. albicans on the surface of tongues, but microbiological study did not prevent the change of CFU of C. albicans cells not only on tongues but also in feces, kidneys and livers. These results suggest that farnesol has very characteristic roles in protection against mucosal candidiasis.