ABSTRACT
Objective:To investigate the fungistatic activity and synergistic effects of natural products and their constituents, including traditional oriental medicines (TOMs).Methods:Fungistatic activities of TOMs prepared by hot-water (115 °C) or ethanol (70%; 40 °C) extraction were determined by their minimum inhibitory concentration. To assess possible synergistic effects, minimum inhibitory concentrations of various combinations were evaluated.Results:By evaluating antifungal susceptibility of Trichophyton rubrum, which is a major causative fungus for several types of dermatophytosis, we confirmed that ethanol extracts were more active than hot-water extracts in 25 of the 36 TOMs, suggesting that the constituents with high hydrophobicity tend to contribute significantly to fungistatic activity. We selected four TOMs with high fungistatic activity, including Aucklandiae radix, Gentianae macrophyllae radix, Scutellariae radix, and Galla rhois, and their synergistic effects were investigated through the combination studies between TOMs or TOM-conventional drug terbinafine. In combinations between four TOMs, partial synergistic effects were observed in Aucklandiae radix–Galla rhois and Gentianae macrophyllae radix–Galla rhois combinations, as supported by the lowest fractional inhibitory concentration index value of 0.66 for both combinations. Furthermore, Galla rhois showed the strongest synergistic effect on growth inhibition of Trichophyton rubrum with a fractional inhibitory concentration index value of 0.50 in combination with terbinafine.Conclusions:Our findings indicate that the combination of TOMs and TOM-terbinafine may be effective on treatment for chronic and recurrent dermatophytosis by improving fungistatic activity and led to decrease systemic toxicity in clinical practice.