A novel naphthazarin derivative, tricrozarin A, has been isolated from the fresh bulbs of Tritonia crocosmaeflora and was characterized as 5,8-dihydroxy-2,3-dimethoxy-6,7-methylenedioxy-1,4-naphthoquinone (2,3-dimethoxy-6,7-methylenedioxynaphthazarin). Tricrozarin A exhibits antimicrobial activity against gram-positive bacteria, fungi, and yeast in vitro and is the first tetra-oxygenated naphthazarin derivative isolated from higher plants.