Fig 2. The diterpenoid 7-keto-sempervirol displays lethal activity against Schistosoma mansoni schistosomula.

Schistosomula (96 well plate format; 1000 parasites/well; triplicate wells for each concentration assessed) were co-cultivated with a 50% dilution series of 7-keto-sempervirol (100, 50, 25, 12.5, 6.25, 3.125, 1.563 μM) at 37°C and 5% CO₂ for 24 hr and subjected to the helminth fluorescent bioassay (HFB). A) Fluorescent data derived from wells were converted into corresponding Log₁₀ values and the mean percentage viability was transformed into probit values to create a dose-response curve as previously described [25]. An LD₅₀ of 19.1 μM was calculated from this dose-response curve. Error bars represent the standard deviation of the mean (SD). B) High content imaging of fluorescently labelled parasites (fluorescein diacetate, green and propidium iodide, red) co-cultured with titrated 7-keto-sempervirol supports the HFB measurements. The concentration of fluorophores employed for high content imaging were the same as previously described for the HFB [25]. Dead control = parasites co-cultured with 70 μM auranofin. DMSO control = parasites co-cultured with 1% (v/v) DMSO. Parasites were imaged at 10 x magnification on a high content imaging system processed by the MetaXpress version 5.10.46 software utilising both FITC and TRITC filters.