Antifungal activity and mechanism of heat-transformed ginsenosides from notoginseng against Epidermophyton floccosum, Trichophyton rubrum, and Trichophyton mentagrophytes

Abstract

Notoginseng, the root of Panax notoginseng, has been used to treat wounds and ulcers for several years in China. However, a rare report was found on the antifungal effect of saponin from notoginseng or a heat-transformed one, particularly against dermatophytes. In this study, notoginseng saponin (NS) was heated in a reaction kettle to produce heat-transformed ginsenoside (HTS). Chromatography and spectroscopic characterization revealed that five polar ginsenosides in NS (notoginsenoside-R1, ginsenoside-Rg1, -Re, -Rb2, -Rd) were almost transformed to three less polar ginsenosides in HTS (ginsenoside-Rk3, -Rh4, -Rh5). HTS showed higher inhibitory activity than that of NS against Epidermophyton floccosum, Trichophyton rubrum, and Trichophyton mentagrophytes, with the lower minimum inhibitory concentration (MIC, 16 or 31.25 μg mL⁻¹) and minimum fungicidal concentration (MFC, 125 or 250 μg mL⁻¹). Moreover, less polar ginsenosides-Rk3, -Rh4, and -Rh5 showed the highest inhibitory activity among the ginsenoside monomers with the lowest MIC (16 μg mL⁻¹) and MFC (62.5 μg mL⁻¹). It was also found that the antifungal activity of individual ginsenosides was negatively correlated with the number of their sugar moieties. Moreover, the antifungal activity of HTS might be attributed to the damage of cell membrane and decrease of membrane potential, easily caused by less polar ginsenosides. Thus, the results indicated that HTS could be applied as antifungal agents to treat ringworm.