If you have any ideas concerning the right concentrations to be use, may be you should make a screening test using differents concentrations from 1-10 microgram/mL of extract or from 10-100.

Initially you can begin with 100 mcg/ml. If you get a positive anti-proliferative activity, you can take different concentrations ranging from 1 to 100 mcg/ml to calculate IC50 value for the extract.

Thank you for your proposals

For the MTT assay I generally used the different concentration of extracts with positive drug as well. The extract concentration I use are in range that is 1, 5, 10, 20, 50, 100, micromole or microgram/ml or microlitre. It helps to study the dose response relationship as well.