Dear Faida Khadidja Idaroussi

I suggest you use DMSO for ethanol (70%). To be precise, prepare a stock solution to 2 mg/mL.

For water extract, make your stock solution with H2O (2 mg/mL).

In the Folin-Ciocalteu method, for the gallic acid curve, the suggested initial concentration is 5 mg/mL.

Hope it helped,

Dear Faida, my suggestion would be to stay with ethanol, 70% ethanol and water. Just try if the ethyl acetate extract is soluble in opure ethanol. For the other two use the solvents which were used for extraction (70% ethanol and water). DMSO has the disadvantage that it has a high boiling point and viscosity. Thus it tends to stick to the evaporated extracts. In this context please also check the answers given to the following closely related question which has been posted earlier on RG:

Which solvent can I use to prepare a stock solution of a plant crude extract?

https://www.researchgate.net/post/Which-solvent-can-I-use-to-prepare-a-stock-solution-of-a-plant-crude-extract

(10 answers)

There are various protocols for using the Folin Ciocalteu method available right here in the "Publications" section of RG. As a typical example please have a look at the following useful article:

Evaluation of the Folin Ciocalteu method and Quantification of Total Tannins in Stem Barks and Pods from Libidibia ferrea (Mart. ex Tul) L. P. Queiroz

https://www.scielo.br/j/babt/a/dH8VxbgFJ6WTk3BGRwcjzDk/?format=pdf&lang=en

(please see attached pdf file)

The following article (and many others!) is freely available as public full ext on RG:

Application of the Folin-Ciocalteu method to the evaluation of Salvia sclarea extracts

Article Application of the Folin-Ciocalteu method to the evaluation ...

Good luck with your work and best wishes, Frank Edelmann

Thank you Diorge Marmitt

Use the solvents with which extracts were got from to avoid insolubility during mixtures.