Antibacterial activity of diosquinone and plumbagin from the root of Diospyros mespiliformis (Hostch) (Ebenaceae)

Diosquinone and plumbagin isolated from the root of Diospyros mespiliformis (Hostch), a common Ingredient in several folk medicines and foods, have been shown to have antibacterial activity against a wide range of organisms. The minimum inhibitory concentrations (MICs) of diosquinone against Staphylococcus aureus NCTC 6571 and S. aureus E3T ranged from 3 to 30 μg/mL, while those against Escherichia coli KL16 and Pseudomonas aeruginosa NCTC 6750 ranged from 15 to 16 μg/mL. MICs were found to increase with the concentration of cells used in the inoculum. Bacterial studies showed that S. aureus NCTC 6571 exhibited a paradoxical biphasic response to dioquinone in nutrient broth, whereas bacterial activity against E. coli KL16 increased with concentration up to the highest concentration of dioquinone tested. Activity against E. coli KL16 was more pronounced in phosphate‐buffered saline than in nutrient broth.