Effect of Flavonols on the Bacteriostatic Action of Dicoumarol

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Abstract
The effect of compds. containing the 7-pyrone structure on the antibacterial action of dicoumarol is discussed. Nutrient broth solns. at pH 6.95 and containing dicoumarol and flavonols were dispensed in 5-ml. amts. in test tubes, sterilized, inoc. with 0.01 ml. of a 16-hr. broth culture of Staphylococcus aureus (F.D.A. 209 P) and incubated at 37[degree]C. The flavonol effect was detd. with a Klett-Summerson photoelectric colorimeter to measure the density of bacterial growth with increasing amts. of flavonols. All flavonols neutralized the bacteriostatic action of dicoumarol. The inhibitory effect of 0.04 mg./ml. of dicoumarol was overcome by 0.05 mg./ml. of rutin and completely neutralized by 0.5 mg./ml. Rutin per se had no effect on the growth of S. aureus. Quercitrin was less effective than rutin; in concs. up to 0.1 mg./ml. it showed increasing antagonism toward dicoumarol and, above this value, the toxic effect began to show up; at 1 mg./ml. there was a 64% inhibition in the growth of S. aureus. Quercetin was least effective; it did not overcome the effect of 0.08 mg./ml. of dicoumarol, and showed only partial antagonism to the lower concns. It completely inhibited S. aureus in a conc. of 0.1 mg./ml.