FIG 4.

Cell viability assay with Leishmania donovani promastigotes. Leishmania promastigotes (2.5 × 10⁶ cells/ml) were used to check the antileishmanial effects of hypericin. Promastigotes were treated with various concentrations of hypericin for 24 h, and cell viability was checked by using the MTT assay. The IC₅₀ obtained for hypericin was 18.00 μM. Promastigotes were also supplemented with trypanothione (0.5 μM) and spermidine (100 μM) and then treated with hypericin. Promastigotes supplemented with trypanothione showed an IC₅₀ of 17.42 μM, which is comparable to that for treated promastigotes without any supplementation. However, promastigotes supplemented with spermidine showed survival rates of ∼90% with IC₅₀ levels of hypericin. *, P < 0.05; **, P < 0.01.