Ability of Ptaeroxylon obliquum to Prevent Adhesion of Candida albicans  

Background: Candidiasis is the most common oral manifestation associated with immuno-compromised patients such as patients suffering from Acquired Immuno Deficiency Syndrome (AIDS), which is of high burden globally, and in South Africa in particular. Cost of current therapies limits access to care. Therefore, there is a need for investigations on cheaper alternative drug therapies. Despite the critical importance of candidal adhesion to human buccal epithelial cells (HBEC) in the pathogenesis of oral candidiasis, only limited amount of information is available on alternative drug therapies to limit adhesion.

Objectives: This study investigated the ability of C. albicans standard strain (ATCC 10231) and two clinical isolates to adhere to human buccal epithelial cells (HBEC) in the presence of P. obliquum acetone leaf extract.

Methods: 250 mg/ml P. obliquum extract was used as the starting material.  HBEC were collected from 20 consenting healthy volunteers aged between 20 and 40-years-old. Amphotericin B was used as positive control and acetone as negative control. The subcidal concentration values for amphotericin B were the concentration slightly below the minimal fungicidal concentration (MFC) of the drug. Adhesion abilities were compared using adaptation to a previously published method. Furthermore, the cytotoxicity of P. obliquum extract was determined.

Results: P. obliquum extract at a concentration ≤250 mg/ml suppressed candidal adhesion to HBEC as effectively as subcidal concentrations of amphotericin B. Graphical illustration of LC₅₀ values demonstrated that 90% candidal adhesion was reached with 20 mg/ml and 50% of candidal adhesion was inhibited by concentrations between 5 and 20 mg/ml depending on the clinical isolates used. Based on the cytotoxicity of P. obliquum extract (LC₅₀=35.58 µg/ml), <20 mg/ml may be of use for clinical application.

Conclusions: This study demonstrated a non-cytotoxic dose-dependant inhibitory effect of P. obliquum extract on the ability of C. albicans strains to adhere to HBEC.