FIGURE 1.

Inhibition of suilysin-induced hemolysis by fisetin: (A) The culture supernatant of SC19 cultures causes sheep erythrocyte hemolysis. Hemolysis was measured by hemoglobin release at OD₅₄₃. (B) Chemical structure of fisetin. (C) After SC19 cultures were incubated with fisetin (0, 2, 4, 8, 16, and 32 μg/ml) at 37°C for 18 h, 125 μl culture supernatant was incubated with 875 μl of PBS containing a 2% defibrinated sheep blood at 37°C for 30 min. Fisetin significantly inhibited the hemolytic activity of the supernatant of SC19 cultured in TSB with 10% newborn bovine serum with 32 μg/ml fisetin. (D) After SC19 was cultured at 37°C for 18 h, 125 μl culture supernatant incubated with fisetin (0, 2, 4, 8, 16, and 32 μg/ml) at 37°C for 30 min was incubated with 875 μl of PBS containing a 2% defibrinated sheep blood at 37°C for 30 min. The inhibitor effect of fisetin on the suilysin in the supernatant of SC19 is dose dependent. Statistical analyses were performed using the two-tailed unpaired t-test. Statistically significant differences are indicated. ^∗P < 0.05; ^∗∗P < 0.01; ^∗∗∗P < 0.001.