Sir,

      It is quite unnecessary to repeat the process once you have done it already. In case, if some other researcher has already done the  phytochemical screening in the plant which you work with, it is necessary and it is a must for you to perform before proceeding  the pharmacological activities.

Good Luck

No. You don't need to do phytochemical screening of extract again after you have successfully done it in the first place. You can proceed to pharmacological activity assay.

I wish you happy research days

It depends on how you stored the samples and for how long. I suggest that you redo the phytochemical analysis just before any pharmacological testing.

regards

Thanks all! for your valuable suggestion, I agree with in performing by my own self though other researchers were done. But I'm going to fractionate the crude methanol extract using different organic solvent, so does analysis of phytochemicals of the crude extract is enough or can I test for both crude and its fractions. Thanks!

@Ebrahim Mohammed

You should test both the crude (as a positive test) and the fractions as well, since the active compounds may not be (probably won't be) in all the fractions. You should also submit an "empty" fraction to guard against false positives, if the people running the assay don't already do so. Likewise, fractions from column chromatography need to be tested for activity as well (assay directed fractionation). Instead of using a detector (such as UV) to see the active compounds, the biological assay is being used as your detector to guide your fractionation.

Extraction process are complete for going to screening is important  for we know identified  secondary metabolite (Glycosides,Alkaloids, Saponine, Flavonoides etc) And which bio- active compound responsible for pharmacological activity.

i agree with Jack Silver. the crude extract is a composition of many molecules. the fractionation will give further separation of chemicals into groups based on their solubility. so each fraction will be with few different class of compounds. it is necessary to screen for phyto chemical compounds of every fraction before pharmacological bio assay. this method is called as bioactivity guided fractionation. once the fraction with maximum biological activity is confirmed that fraction will be subjected for chemical isolation to identify the phyto chemicals responsible for the activity.

No, it is not necessary to perform again, I suggest that you store your dry extracts in the refrigerator at 4 ° C and you continue your manipulations