Evaluation of the concentrations of curcuma longa (turmeric) essential oil to cause fungistasis and inhibit melanogenesis in the fungus Neoscytalidium dimidiatum   

Abstract Neoscytalidium dimidiatum, a cause of onychomycosis and tinea pedis, produces melanin, a virulence factor. In this study, we aimed to do 2 things: 1) determine the concentration of Curcuma longa (turmeric) essential oil to be fungistatic against N. dimidiatum in vitro and 2) determine the ability of Curcuma longa (turmeric) essential oil to prevent melanogenesis (a virulence factor) by N. dimidiatum in vitro in order to determine its potential use as an antifungal agent. The testing was done using 10 clinical isolates of N. dimidiatum. The concentrations of turmeric essential oil used for this study ranged from 2% to 20%. Sensitivity testing was done using an agar dilution method with a 7-day incubation period to determine the minimal inhibitory dilution. The ability to inhibit melanogenesis was evaluated by comparing the amount of melanin between untreated isolates and isolates treated with either 4% or 10% turmeric essential oil. Melanin detection was accomplished using melanin-specific monoclonal antibody (Mab) 8D6 and measuring the immunofluorescence using an immunofluorescent microscope at 1,000x magnification. The concentration of turmeric essential oil that significantly inhibited N. dimidiatum growth was the 20% solution. The 4% and 10% turmeric essential oil preparation treated isolates of N. dimidiatum gave significantly lower (1.592 (p=0.001) and 1.705 (p=0.003)) mean fluorescent intensities than the untreated isolate (7.575). In summary, 20% turmeric essential oil significantly inhibited N. dimidiatum growth and both 4% and 10% turmeric essential oil samples inhibited melanogenesis. We conclude turmeric essential oil has therapeutic potential for use against infections caused by N. dimidiatum. Further studies are needed to determine what the antifungal mechanism is and if it can be used in vivo to treatment these infections.

วารสาร : Southeast Asian Journal of Tropical Medicine and Public Health, 54(6), 301-313.

Keyword : Curcuma longa (turmeric) essential oil, fungistatic, melanogenesis, Neoscytalidium dimidiatum, onychomycosis