I am planning to evaluate the hepatoprotective activity(Prophylactic) of the plant extract,in this regard to establish the acceptable data is it necessary to perform curative study also?
I think you are planning to evaluate in vitro hepatoprotective activity of the plant extract which should be followed by curative study. Because in vivo studies always prove your evaluation within the physiological condition.
Prophylaxis/prevention might well occur by a different mechanism of action than curation. Thus proven activity in one area is not necessarily to be expected in the other.