Table 1.

In vitro biological assays. Leishmania infantum logarithmic phase promastigotes were incubated with b-AD (0–61.96 μM) or AmpB (0–1.08 μM) for 48 h at 24 °C. Cell viability was analyzed by the MTT method and the 50% Leishmania inhibitory concentration (IC₅₀) was calculated by applying sigmoidal regression of dose-response curve. Murine macrophages were also incubated with b-AD (0–123.92 μM) or AmpB (0–10.82 μM) for 48 h at 37 °C in 5% CO₂, and the 50% cell inhibitory concentration (CC₅₀) was also evaluated by a dose-response curve. The selectivity index (SI) was calculated by the ratio between the CC₅₀ and IC₅₀ values. The 50% human red blood cells inhibitory concentration (RBC₅₀) was determined by incubating the 5% red cell suspension with b-AD (0–123.92 μM) or AmpB (0–10.82 μM) for 1 h at 37 °C in 5% CO₂. The lysis percentage was evaluated spectrophotometrically, and the absence or presence of hemolysis were determined by replacing b-AD for PBS or distilled water, respectively. Results are shown as mean ± standard deviation of the groups.

Compound	IC50 (μM)	CC50 (μM)	SI	RBC50 (μM)
β-acetyl-digitoxin	20.94 ± 2.60	453.04 ± 23.29	21.64	334.95 ± 24.90
Amphotericin B	0.11 ± 0.03	0.86 ± 0.11	7.82	12.66 ± 1.52