24-h IC50a MICb Test compound 24-h IC50a MICb RDCFc RDCOd RDCFc RDCOd Flor* 1.49 (0.06) 0.36 (0)         Oxy** 0.12 (0.02) 0.46 (0)         1 2.24 (0.37) 7.47 (0) 1.5 (0.3) 19.7 (6.4) 20.8 (0) 16.2 (0) 2 2.1 (0.08) 7.47 (0) 1.4 (0) 17.9 (2.4) 20.8 (0) 16.2 (0) 3 2.1 (0.08) 4.11 (3.36) 1.4 (0) 17.9 (2.4) 11.5 (9.4) 8.9 (7.3) 4 1.87 (0.23) 4.11 (3.36) 1.3 (0.2) 16.3 (4.6) 11.5 (9.4) 8.9 (7.3) Mix 1.76 (0.04) 4.11 (3.36) 1.2 (0) 15.0 (2.2) 11.5 (9.4) 8.9 (7.3)

*Florfenicol; **Oxytetracyline HCl a24-h IC50 = 50% inhibition concentration in mg/L. bMIC = Minimum inhibitory concentration in mg/L. cRDCF = Relative-to-drug-control florfenicol; values closer to 1.0 indicate higher antibacterial activity compared to florfenicol. dRDCO = Relative-to-drug-control oxytetracycline; values closer to 1.0 indicate higher antibacterial activity compared to oxytetracycline.

Table 4: Results of the bioassay evaluation of antimicrobial compounds from American sycamore leaves for antibacterial activity against Streptococcus iniae LA94-426. Numbers in parentheses are the standard error of the mean