Antimicrobial activities of 1,2-dihydroxyanthraquinone derivatives against food-borne bacteria

The antimicrobial activities of materials derived from Cassia obtusifolia seeds were evaluated against the seven food-borne bacteria. The active constituent of C. obtusifolia seeds was isolated using various chromatographic techniques and characterized as 1,2-dihydroxyanthraquinone (alizarin). The purified alizarin exhibited weak activity against Bacillus cereus (clean zone diameter, 11.0 mm), and moderate activity against Staphylococcus epidermidis (17.5 mm) and Salmonella enterica (16.2 mm) at 2.0 mg/disc. When compared with alizarin analogues, alizarin-3-methyliminodiacetic acid exhibited the strongest antimicrobial activity against B. cereus, S. intermedius, S. epidermidis, and S. enterica at 2.0 mg/disc, whereas the other analogues exhibited no antimicrobial activity against the seven food-borne bacteria. Taken together, these results indicate that alizarin isolated from C. obtusifolia seeds and its structural analogues may be useful as natural preservatives.