Rumex japonicus Houtt. leaves: the chemical composition and anti-fungal activity.

Background: Candida albicans is a pathogenic commensal fungus. Trichophyton mentagrophytes and Trichophyton rubrum are the leading pathogens of dermatophysis. Rumex japonicus Houtt. has a miraculous effect on the treatment of tinea skin disease, but its mechanism has not been clarified.

Purpose: This paper investigated the anti-fungal ingredients of the leaves of Rumex japonicus Houtt. (RJH-L) and the mechanism of the anti-fungal (Trichophyton mentagrophytes, Trichophyton rubrum and Candida albicans).

Method: First, the chemical composition analysis of RJH-L was conducted by acid extraction and alcohol precipitation, high performance liquid chromatography (HPLC) and nuclear magnetic resonance spectroscopy (NMR); in vitro anti-fungal experiments were carried out, including the minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC) spore germination rate, germ tube production rate, nucleic acid and protein leakage rate, biofilm structure, PCR, etc., to study the mechanism of action of RJH-L anti-fungal and anti-biofilm activity.

Result: Seven monomer compounds were obtained: anthraquinones (rhein, emodin and aloe-emodin); polyphenols (ferulic acid, p-coumaric acid), and flavonoids (rutin and quercetin). The results of in vitro anti-fungal experiments showed that the extracts of RJH-L had strong inhibitory effect on both fungi (MIC: 1.96 µg/mL-62.50 µg/mL), of which emodin had the strongest effect on Trichophyton mentagrophytes; and rhein had the strongest effect on Candida albicans and Trichophyton rubrum. The above active components can inhibit the germination of fungal spores and germ tube, change cell membrane permeability, prevent hyphal growth, destroy the biofilm structure, and down-regulate the expression of agglutinin-like sequencefamily1 of biofilm growth.

Conclusion: This study shows that RJH-L are rich in polyphenols, flavonoids, and anthraquinones, and play a fungicidal role.