Studies on the antifungal effects of Hinokitiol on Candida albicans: inhibition of germ tube formation and synergistic pharmacological effects of miconazole

One of the goals of oral healthcare management is to manage dry mouth. Thus, moisturizers containing antimicrobial ingredients, such as hinokitiol (HT), are applied to the oral mucosa after oral care. In this study, we investigated the preventive effect of HT against the growth of Candida albicans (C. al) and its synergistic effect when combined with miconazole (MCZ), an oral treatment for candidiasis. As the concentration of HT increased, the length and percentage of germ tubes (GT) decreased. Larger inhibition circles were observed for MCZ concentrations of 2.0 and 4.0 mu g/disc compared to the HT medium without HT. The increased inhibitory effect was observed in both aerobic and anaerobic cultures. This suggests that the production of reactive oxygen species (ROS) by C. al cells increased with the combination of HT and MCZ. The length and percentage of GT increased, whereas the amount of ROS decreased when ROS scavengers were used in combination with the drug. HT led to morphological changes that inhibited the GT associated with pathogenic C. al, exhibited a complementary action against MCZ, and showed a possible association with hydrogen peroxide and superhydroxy anion radicals. These effects suggest that HT is a promising candidate for inhibiting C. al. In conclusion, HT demonstrated a prophylactic effect by inhibiting C. al and a synergistic effect with MCZ, a drug used to treat oral candidiasis. HT may also be useful for suppressing the onset and reducing the severity of oral candidiasis.