Dear Prakash Kumar

You could try the described protocols in these manuscripts:

Article The first assessment on antioxidant and antidiabetic activit...

Article Serviceberry, a berry fruit with growing interest of industr...

Article Application of sensory, nutraceutical and genetic techniques...

Prakash Kumar Sir, Firstly you have to prepare the crude extract of the dried leaves in the desired solvent. The crude extract is used for checking the TPC & TFC of the leaves.

Briefly, Folin-ciocalteu & aluminum chloride colorimetric assays were used for the quantitative estimation of TPC & TFC respectively.

For antioxidant activity, different assays like DPPH, ABTS, H2O2, hydroxyl radical can be used.

Please see the attached paper:

"Preliminary phytochemical screening and In vitro antioxidant activities of the aqueous extract of Helichrysum longifolium DC"

Hope this will help.

Thanks

Check https://www.hindawi.com/journals/tswj/2020/8780704/

Also check https://www.mdpi.com/2071-1050/12/20/8586/pdf

Check on what this paper used.

Article Comprehensive study on the antioxidant capacity and phenolic...