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Several human pathogenic fungi can acquire resistance against the available antifungal compounds or need prolonged time of therapy,
which may cause toxicity. Thymol, thymoquinone (TQ) and thymohydroquinone (THQ) are principle constituents of the essential
oil of Nigella sativa seeds. TQ and THQ were organically synthesized from thymol in our laboratory. The chemical structure and purity were confirmed by using GC-MS analysis. The three compounds were primary tested at concentration of 1mg/ ml for their preliminary antifungal effect against thirty human pathogens isolated from patients. The tested pathogens were eleven dermatophyte, eight yeast and eleven mold isolates. All of the three compounds showed 100% inhibition for the thirty pathogens at concentration of 1mg/ ml. The minimum inhibitory concentration (MIC) test of each compound was studied on eight dermatophyte, five yeast and five mold isolates. Thymoquinone was the best antifungal compound against all of the tested dermatophytes and yeasts, followed by thymohydroquinone and thymol respectively. Thymol was the best antifungal against molds followed by TQ and THQ respectively.
Keywords: Nigella sativa, thymol, thymoquinone, thymohydroquinone, antifungal, dermatophytes.