A novel compound, benthophoenin [1], was isolated from the mycelium of Streptomyces prunicolor. The structure of 1 was determined mainly by nmr spectral analysis to be a phenazine carboxylic acid with a geranyl and two benzoyl residues. Free radicals including active oxygen species cause a variety of diseases such as inflammation, autoimmune disease, diabetes, rheumatism, cardiovascular diseases, and cancer initiation (1-3). These diseases have been reported to be ameliorated by free radical scavengers (4). In the course of our screening for free radical scavengers to ameliorate these diseases, we isolated naphterpin (5), antiostatins (6), pyridoxatin (7), benthocyanin A (8), and stealthins (9). Detailed investigation of minor components of benthocyanins (10) produced by Streptomyces prunicolor 1884-SVT2 has resulted in the isolation of a novel compound designated benthophoenin [1]. Compound 1 is a phenazine carboxylic acid with benzoyl moieties at the C-3 and C-7 positions and a geranyl substituent at a nitrogen and shows structural similarity to benthocyanin A (3). We report herein its isolation and structure determination.