Antibacterial and antifungal activities of indican (indoxyl -D-glucoside)

Indican (Indoxyl β-d-glucoside), plant pigments found in true Indigo, are present in Indigofera genus plants, fungi and human urine. This study evaluated the antibacterial and antifungal activities of this pigment using the microdilution method. Antibacterial and antifungal activities were performed against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Candida albicans, Candida tropicalis, Candida krusei, Trichophyton rubrum, Trichophyton mentagrophytes and Microsporum gypseun. Minimum inhibitory concentrations (MICs) were measured according to the broth microdilution protocols by the Clinical and Laboratory Standards Institute (CLSI). The Indican showed only antifungal activity. It had MIC values of 128 µg/mL for yeasts and 512 µg/mL for most of the dermatophytes. The minimum fungicidal concentration (MFC) values of the Indican ranged between 512 μg/mL: C. tropicalis (LM-6) and C. krusei (LM-6 and LM-8) and 1,024 μg/mL: C. albicans (ATCC-76645, LM-108, LM-P20). Further studies are needed to clarify the potential fungicidal activity of the Indican and the possibility for topical applications. Key words: Antibacterial activity, antifungal activity, indican.