How to calculate the dosage of drugs from unknown MW? - Working with crude extract.. (May/21/2008 )

Forumers,

Im working with crude plant extract and preparing the concentration of crude extracts : 10mg/ml, 100mg/ml and 1000mg/ml dissolved in normal saline. The MW of the extracts were unknown.

The problem is how to set up the dosage in mg/kg in rats?

How many mL's should I give to rat? I had planned to give it oral route.

Thanks

I am no expert in this field, but to me it seems when you are using a crude extract (many components?), you can't possibly set a dosage in terms of MW. You may just have to try a wide range as you have suggested yourself, unless you find in literature a similar extract used in rats or some other animals (in which case you extrapolate using body weight comparison).