Antifungal Activity of Rockrose (Cistus ladanifer) Decoction Extracts against Planktonic Cells and Biofilms of Candida spp.: An in vitro Study

Background: Candida infections remain a significant clinical concern due to their increasing tolerance and resistance to antifungal agents, as well as the limited efficacy of current treatments. Beyond planktonic growth, Candida spp. can form highly structured biofilms embedded in an extracellular matrix, which markedly increases their persistence and antifungal tolerance [1]. Species such as Candida albicans, C. glabrata, C. tropicalis and C. parapsilosis are frequently implicated in human disease, and novel bioactive compounds capable of targeting both planktonic cells and biofilms are urgently needed. Cistus ladanifer, a Mediterranean plant rich in phenolic and terpenoid compounds, has been reported to exhibit antimicrobial activity, making it a promising natural alternative. Objective: This study aimed to evaluate the antifungal potential of C. ladanifer decoction extracts against planktonic and biofilm-associated Candida spp [1-3]. Methods: Minimum Inhibitory Concentration (MIC) assays were performed according to EUCAST guidelines (50–1500 mg/L). Minimum Fungicidal Concentration (MFC) was determined by CFU quantification after serial dilutions and SDA plating. To assess biofilm susceptibility, Minimum Biofilm Eradication Concentration (MBEC) assays were conducted using 24h pre‑formed biofilms in 96‑well plates. Biofilms were exposed to fresh RPMI‑1640 containing extract concentrations higher than those used for MIC and MFC. The plates were incubated for 24 h at 37 °C. Viability was quantified by CFU enumeration (Log₁₀ CFU/cm²). Total biomass was assessed by Crystal Violet staining, with absorbance measured at 570 nm. Results: The decoction extracts exhibited antifungal activity against all Candida species tested, with MIC values matching MFC. Susceptibility varied among species, confirming species‑dependent sensitivity to C. ladanifer extracts. MBEC and biomass analyses revealed reductions in viable biofilm cells and total biofilm mass following exposure to the extracts, indicating potential anti‑biofilm effects. Conclusion: Cistus ladanifer decoction extracts demonstrate measurable antifungal activity, affecting both planktonic cells and biofilms in a species‑dependent manner. These findings support the potential of plant‑derived compounds as complementary strategies for controlling Candida infections.