Abstract: Trichophyton rubrum (T. rubrum) is an important pathogen causing dermatophytosis. The dry twig and leaf of Platycladus orientalis (L.) Franco is called Cacumen Platycladi and recorded in the "Miao Medicine" for the treatment of tineas. The study aimed to investigate the main anti-T. rubrum components and mechanisms of Cacumen Platycladi, and to provide potential candidate anti-T. rubrum agents. In this study, the antifungal activity of Cacumen Platycladi main ingredient against T. rubrum was determined by minimum inhibitory concentration and spore germination rates. The mycelial morphology and spores ultrastructure of T. rubrum were observed by using electron microscopy; and the effects of the active substances of Cacumen Platycladi on the permeability, integrity, and ergosterol content of T. rubrum cell membrane were further examined, so as to elucidate the mechanism of T. rubrum inhibition by the active substances of Cacumen Platycladi. Finally, we used GC-MS and qRT-PCR to find its target of action against T. rubrum. The results showed that the petroleum ether fraction of Cacumen Platycladi exhibited the strongest anti-T. rubrum activity and in which α-pinene was proved to be the main ingredient with a MIC 32 μg·mL^-1. Alpha-pinene could induce membrane damage, higher significant cellular leakage (P<0.01) and ergosterol and 24(28)dehydroergosterol amount significant decreasing within 24 h (P<0.05); Cause highly significant reduction (P<0.01) of the relative expression of ERG3 gene and the "ERG3 inhibition" related mark sterol Ergosta-7,22-dien-3β-ol occured in sterols pattern. The results showed that α-pinene is the most potent anti-T. rubrum component in Cacumen Platycladi and ERG3 was its target.

Key words: Trichophyton rubrum, Cacumen Platycladi, α-pinene, cell membrane, ergosterol, ERG3