Use the calibration curve to find the equivalent gallic acid concentration for your sample based on absorbance.

Then calculate TPC using:

TPC=C×VxDF/m

Where:

• C = concentration from calibration curve (mg/L of gallic acid equivalents)
• V = volume of extract used (in L)
• m = mass of plant extract used (in g)
• DF=dilute factors
• Use this formula and calculate total phenol contents in different plant extracts and express in mg of GE/g.

Determination of polyphenol content using Folin-Ciocalteu

1 Preparation of Folin-Ciocalteu reagent (0.25 mol/L)

2 Preparation of 15% Na2CO3 solution (W/V)

3 Preparation of standard solution to obtain reference standard solution.

4 Drawing of standard solution standard curve

5 Preparation of sample solution

6 Calculation of polyphenol content according to the formula

We have more than one method. It's, depends on methods. And we must prepare standard curve by catechin, tannic acid or vanillic acid

Hello

Here is a useful article that you will find the exact method for Folin-Ciocalteu method to determine TPC, read it carefully, i hope it works

https://www.researchgate.net/publication/369949412_Effect_of_Rosemary_and_Marjoram_Extracts_on_Oxidative_Stability_of_Refined_Sunflower_Oil