Inhibitory effect and safety of Angelica dahurica–Ligusticum sinense extracts against Malassezia furfur and its biofilms

OBJECTIVE: To evaluate the in vitro inhibitory activity of different Angelica dahurica-Ligusticum sinense extracts (ethanolic, aqueous, and cold-pressed) against planktonic cells and biofilms of Malassezia furfur. METHODS: Ultra-performance liquid chromatography (UPLC) was used to quantify the major constituents. Micro-broth dilution determined the minimum inhibitory concentration (MIC), and time-kill assays assessed fungicidal kinetics. Crystal violet staining assay (CVA) and XTT reduction assays quantified inhibition of biofilm biomass formation/metabolic activity and reduction of mature biofilms. Dermal irritation of the ethanolic extract was evaluated in rats. RESULTS: UPLC showed that the ethanolic extract contained the highest levels of ferulic acid, bergapten, oxypeucedanin, imperatorin, and isoimperatorin. The MIC of the ethanolic extract was 5 mg/mL, superior to those of the aqueous and cold-pressed extracts (10 mg/mL each). A time-kill study revealed rapid fungicidal activity at 8 × MIC. Biofilm assays demonstrated that 0.5× and 1 × MIC of the ethanolic extract significantly inhibited biofilm formation (P < 0.05), whereas 8 × MIC effectively eradicated pre-formed biofilms, markedly reducing biomass and metabolic activity (P < 0.01). No cutaneous irritation was observed in rats at 8 × MIC. CONCLUSION: The A. dahurica-L. sinense ethanolic extract potently inhibited and eradicated M. furfur planktonic cells and biofilms with favorable safety. This activity may be attributable to its high content of coumarins and phenolic acids, suggesting its potential as a natural agent for the treatment of M. furfur-associated skin disorders.