Oregano and clove essential oils induce surface alteration of Saccharomyces cerevisiae.

The antimicrobial properties of volatile aromatic oils have been recognized since antiquity. Oregano and clove oils have been shown to possess a broad spectrum of antimicrobial activity. In this paper, the fungicidal action of these two essential oils was studied on the yeast model Saccharomyces cerevisiae. Yeast cell lysis was shown by the release of substances absorbing at 260 nm. In addition, scanning electron microscopy analyses revealed that the surface of treated cells by oregano and clove oils was significantly damaged.

Study of anticandidal activity of carvacrol and eugenol in vitro and in vivo.

BACKGROUND/AIMS: The mechanism of the anticandidal action of the major phenolic components of oregano and clove essential oils - carvacrol and eugenol - was studied. This activity was also evaluated for the therapeutic efficacy in the treatment of the experimental oral candidiasis induced by Candida albicans in immunosuppressed rats. METHODS: In vitro, the addition of carvacrol at 0.1% or eugenol at 0.2% during the exponential growth of C. albicans was evaluated. The release of substances absorbing at 280 nm by cells treated with these two components was also measured spectrophotometrically. In vivo, oral candidiasis in immunosuppressed rats was established by inoculating 3 x 10(8) cells of C. albicans with a cotton swab on three alternate days. The number of colony counts was evaluated from the oral cavity of rats treated for eight consecutive days with carvacrol, eugenol or nystatin and compared to untreated controls. RESULTS: Carvacrol and eugenol were fungicidal in exponentially growing C. albicans. Interestingly, this fungicidal effect was accompanied by the release of substances absorbing at 280 nm. In an immunosuppressed rat model of oral candidiasis, carvacrol or eugenol treatment significantly (P < 0.05) reduced the number of colony counts sampled from the oral cavity of rats treated for eight consecutive days compared to untreated control rats. Similar results were obtained with nystatin used as a reference treatment. CONCLUSION: The in vitro results indicated that both carvacrol and eugenol exerted an anticandidal effect by a mechanism implicating an important envelope damage. Their in vivo efficacy on experimental oral candidiasis leads us to consider them as possible antifungal agents.

Antifungal treatment with carvacrol and eugenol of oral candidiasis in immunosuppressed rats.

Carvacrol and eugenol, the main (phenolic) components of essential oils of some aromatic plants, were evaluated for their therapeutic efficacy in the treatment of experimental oral candidiasis induced by Candida albicans in immunosuppressed rats. This anticandidal activity was analyzed by microbiological and histopathological techniques, and it was compared with that of nystatin, which was used as a positive control. Microbiologically, carvacrol and eugenol significantly (p<0.05) reduced the number of colony forming units (CFU) sampled from the oral cavity of rats treated for eight consecutive days, compared to untreated control rats. Treatment with nystatin gave similar results. Histologically, the untreated control animals showed numerous hyphae on the epithelium of the dorsal surface of the tongue. In contrast no hyphal colonization of the epithelium was seen in carvacrol-treated animals, while in rats treated with eugenol, only a few focalized zones of the dorsal surface of the tongue were occupied by hyphae. In the nystatin treated group, hyphae were found in the folds of the tongue mucosa. Thus, the histological data were confirmed by the microbiological tests for carvacrol and eugenol, but not for the nystatin-treated group. Therefore, carvacrol and eugenol could be considered as strong antifungal agents and could be proposed as therapeutic agents for oral candidiasis.

Evaluation of carvacrol and eugenol as prophylaxis and treatment of vaginal candidiasis in an immunosuppressed rat model.

OBJECTIVES: Anticandidal activity of carvacrol and eugenol, the major phenolic components of oregano and clove essential oils, respectively, were tested in vivo. METHODS: Efficacy evaluation of carvacrol and eugenol in the prophylaxis and treatment of experimental vaginal candidiasis was performed in immunosuppressed rats. The anticandidal activity was analysed by microbiological and histological techniques and was compared with that of nystatin. RESULTS: Microbiologically, prophylactic treatment with carvacrol eradicated the vaginal fungal burden of infected rats, whereas eugenol reduced the number of colony counts of Candida albicans in vaginas of infected rats by 98.9% 10 days after inoculation. Therapeutic treatment for 7 consecutive days with carvacrol was able to eradicate the vaginal candidal burden in 7/9 of the infected rats and reduced the number of colony counts of C. albicans in vaginas of the two remaining rats by 98%. Treatment with eugenol completely cured 2/9 of the infected animals, but the 7/9 still infected showed an 84% reduction of colony counts of C. albicans in their vaginas. Histologically, in all treated rats, no Candida organisms were found in the lumina of the vagina; this was in contrast to control groups in which many yeasts, strongly stained with periodic acid-Schiff, were observed. The results obtained with nystatin used at 10-fold minimal inhibitory concentration confirm the validity of this model. CONCLUSIONS: Carvacrol and eugenol could be considered as promising products in the treatment of vaginal candidiasis. This work is a preliminary contribution to the development of a new generation of efficient and natural antifungal agents for curative treatment and prophylaxis.

Antifungal treatment with carvacrol and eugenol of oral candidiasis in immunosuppressed rats

Carvacrol and eugenol, the main (phenolic) components of essential oils of some aromatic plants, were evaluated for their therapeutic efficacy in the treatment of experimental oral candidiasis induced by Candida albicans in immunosuppressed rats. This anticandidal activity was analyzed by microbiological and histopathological techniques, and it was compared with that of nystatin, which was used as a positive control. Microbiologically, carvacrol and eugenol significantly (p<0.05) reduced the number of colony forming units (CFU) sampled from the oral cavity of rats treated for eight consecutive days, compared to untreated control rats. Treatment with nystatin gave similar results. Histologically, the untreated control animals showed numerous hyphae on the epithelium of the dorsal surface of the tongue. In contrast no hyphal colonization of the epithelium was seen in carvacrol-treated animals, while in rats treated with eugenol, only a few focalized zones of the dorsal surface of the tongue were occupied by hyphae. In the nystatin treated group, hyphae were found in the folds of the tongue mucosa. Thus, the histological data were confirmed by the microbiological tests for carvacrol and eugenol, but not for the nystatin-treated group. Therefore, carvacrol and eugenol could be considered as strong antifungal agents and could be proposed as therapeutic agents for oral candidiasis.

Surface alteration of Saccharomyces cerevisiae induced by thymol and eugenol.

AIMS: This study aims to bring some information about the mechanism of the fungicidal action of thymol and eugenol; phenolic major components of thyme and clove essential oils respectively. Saccharomyces cerevisiae was used as yeast model. METHODS AND RESULTS: Treatment of yeast cells with these components led to their lysis as shown by the release of substances absorbing at 260 nm. In addition, scanning electron microscope observations revealed that the surface of the treated cells was significantly damaged. CONCLUSIONS: Antifungal activity of thymol and eugenol involve alteration of both membrane and cell wall of the yeast. SIGNIFICANCE AND IMPACT OF THE STUDY: This work is a preliminary contribution aiming to develop a new generation of efficient and natural antifungal agents.

Influence of the environmental temperature on the post-partum testosterone surge in the rat.

In the neonatal male rat, a rapid and transient increase in serum testosterone occurs about 2 h after birth. This post-partum testosterone surge (PPTS) has been implicated in the masculinization and defeminization of the central nervous system. The present study shows that environmental temperature can have a profound influence on the PPTS. Male rats were delivered from their mothers by caesarean section on day 22 of gestation. Immediately thereafter, neonatal males were placed at an ambient temperature of either 18, 21, 24 or 30 degrees C. With 2 h of exposure, the body temperature was in close correspondence with the ambient temperature. The PPTS was clearly abolished in the pups exposed for 2 h at either 18 or 21 degrees C. The effect of temperature was reversible: by placing pups at either 18 or 21 degrees C for 2 h after delivery, and then rewarming by placing them with a foster mother, the PPTS was delayed until 4 h after birth, i.e. 2 h after the beginning of rewarming. Thus, environmental cooling appears to retard the development of neural and/or endocrine systems mediating the PPTS. Aberrant maternal care which would produce substantial cooling of the male pups would be expected to affect the PPTS, which in turn might affect the sexuality of male progeny.

Testicular hormones during the first few hours after birth augment the tendency of adult male rats to mount receptive females.

In the male rat, a dramatic increase in serum testosterone of testicular origin occurs during the first two hours of postnatal life. This experiment was designed to determine whether this increase contributes to the development of the propensity for adult male rats to mount sexually receptive females. Male rats were castrated at either 0-hours (virtually at the moment of birth), or at 6 hours, or at 24 hours after birth. Some males castrated at 0-hours were injected with 1 microgram of testosterone after surgery. Control males were sham-operated at birth, and castrated in adulthood. At about 90 days of age, each male was given testosterone replacement therapy and tested over a period of 6 weeks for mounting. Castration of newborn males retards the development of mounting in the sense that males castrated at 0-hours require a longer period of hormone stimulation before beginning to mount, a greater percentage of males castrated at 0-hours fail to mount altogether, and even those who do mount do so at a frequency significantly lower than that for males castrated later in life. These effects are not seen when males are given an injection of testosterone immediately after castration at 0-hours, or when castration occurs at 6 hours after birth or later. We conclude that gonadal hormonal stimulation during the first several hours after birth contributes to, although is perhaps not essential for, the development of mounting.

[Effect of newborn rat testes on the male sexual behavior of the testosterone-treated adult]. / Influence des testicules du rat nouveau-né sur le comportement sexuel mâle de l'adulte soumis à la testostérone.

Neonatal male rats were castrated either at 0, 6 or 24 hrs. after birth. As adults, testosterone was delivered by subcutaneous implantation of a Silastic capsule containing this hormone. The probability to display mounting behavior in presence of an estrous female was lower when the animals were castrated at 0 hr. than at 6 or 24 hrs. or when they received a subcutaneous injection of 1 microgram of testosterone propionate, at the time of castration at 0 hr. These results suggest that in the rat, during the 6 hrs. following birth, neonatal testes influence the sensitivity of the adult central nervous system to testosterone.