A saframycin-non-producing mutant of Streptomyces lavendulae IFM 1291 was found to produce a new tyrosine-derived indicator pigment SL-1 with anti-dermatophyte activity. This study describes the isolation, structural elucidation, and biological properties of SL-1, particularly its antimicrobial activity against dermatophytes. SL-1 was isolated from the mutant's culture broth via fermentation, solvent extraction, and column chromatography. Its structure was identified as (E)-1,2-dihydroxy-4-(2-nitroethenyl)benzene using electron ion mass spectrometry, nuclear magnetic resonance, and synthetic verification (synthesized from 3,4-dihydroxybenzaldehyde, matching the natural pigment in all respects). Biological assays revealed moderate inhibitory activity against Gram-positive bacteria (e.g., Streptococcus pyogenes, Brucella abortus), anti-dermatophyte activity (with specific MIC values), sensitivity of the producer strain to SL-1, and moderate cytocidal activity against cultured L1210 leukemic cells (ED50 = 1.0 μg/ml). This is the first report of SL-1 isolation from natural sources.