Hi,

usually phenolic content is measured using the Folin-Ciocalteau assay and a phenolic acid (such as gallic acid) to set up a calibration curve.Then you use the equation C (GAE) = c x V/M (where c = concentration determined from standard curve (mg/ml), V = volume used during the assay (mL), and M = mass of the extract used during the assay (g) and will give GAE in mg/g extract. You will find a protocol in this article: http://www.sciencedirect.com/science/article/pii/S0963996911002754

Hope it helps!

hi vitor, thanks for the reply. What about the formula for calculating total flavonoid content? Is it same as TPC?

Yes it is, but instead of using gallic acid as a standard you should use quercetin or rutin.

okay now I understand, thanks a lot :-)

I have another question is it possible that the value of total flavonoid expressed as rutin equivelant (mg/g) being more than the value of total phenolic content expressed as gallic acid equivelant (mg/g) specially the major isolated compound from plant under investigation is rutin

thanks for help

Can i ask you my analyse.

i extracted 2,5 g dry weight in 250 ml solution. then i used 0,5 ml extract and diluted it with dH2O, FCR and sodium carbonate to 12,5 ml total value. i read absorbance at 750 nm. i prepared gallic acid standard curve as mg/l and my exuation is y=0,0059x. so when i use the curve i calculated the value as 34 mg/l. can anyone help me to find the final concantration as mg/100 g dry weight? thanks!

The amount of total phenolics is determined with the Folin- Ciocalteu reagent using Gallic acid as a standard and the total phenolics is expressed as mg/g gallic acid equivalents (GAE). Concentration of 0.01, 0.02, 0.03, 0.04 and 0.05 mg/ml of gallic acid are prepared in methanol. Concentration of 0.1 and 1mg/ml of plant extract is also prepared in methanol and 0.5ml of sample is introduced into test tubes and mixed with 2.5ml of a 10 fold dilute Folin- Ciocalteu reagent and 2ml of 7.5% sodium carbonate. The tubes are covered and allowed to stand for 30 minutes at room temperature and then the absorbance is at read at 760 nm on UV/VIs spectrophotometer. The Folin-Ciocalteu reagent is sensitive to reducing compounds including polyphenols, thereby producing a blue colour upon reaction. This blue colour is measured spectrophotometrically. The two attached file will provide you step by step laboratory protol for TPC estimation.

Hello, this topic has been already disscused, but as far as I had some troubles with calculations, this paper helped me to solve it. Hope it is going to be useful for you as well. 

http://pelagiaresearchlibrary.com/asian-journal-of-plant-science/vol3-iss1/AJPSR-2013-3-1-69-74.pdf

Regarding the determination of TPC with the Folin-Ciocalteu method, please be aware that the presence of ascorbic acid or other reducing substances interfere in the final result. Please consult also the paper: "The Folin–Ciocalteu assay revisited: improvement of its specificity for total phenolic content determination", DOI: 10.1039/C3AY41125G, 

http://pubs.rsc.org/en/Content/ArticleLanding/2013/AY/c3ay41125g#!divAbstract

Hi Parsa, from the calibration curve, you obtain an equation [y = mx + b] which expresses the linear relationship between the concentration of your standard (usually gallic acid) (i.e., x) and absorbance (i.e., y). Thus, absorbance = slope (concentration) + y-intercept. You now use this equation to calculate for the unknown concentration of phenolics in your sample solution given its known absorbance. The result is expressed as gallic acid equivalent if you used gallic acid as your standard to construct the calibration curve. Gallic acid represents all other phenolics in your sample solution (since it is impossible to use as many standards as the number of phenolics in your sample), thus, the term gallic acid equivalent. When other phenolic compounds like tannic acid, quercetin, cathecin, etc are used as standard instead of gallic acid, the expression changes corresponding to the standard used.

Question:

What is does "specific # " mean in the below equation:-

Phenolic % = (V-Vo) x Phenolic equivalent in 1 ml of 0.1N of KMnO4 (aq.) x 250x 100 /  

                          g x 25

and what does "Phenolic equivalent in 1 ml of 0.1N of KMnO4 (aq.)" mean?

Hello! It seems that I have the same problem for apple pomace TP content.

I have 1 g dried apple pomace extracted in 25 mL methanol and the TP content obtain from the gallic acid curve was 160 g GAE/mL. How can I express the TP content in mg GAE/100 g dried pomace.

Thank u!

The calculation of total phenolic contents in a plant extract sample will be as follows

T =Cx V/M .

T is the total phenolic content in mg·g–1 of the extracts as

GAE, C is the concentration of gallic acid established

from the calibration curve in mg·ml–1, V is the volume of

the extract solution in ml and M is the weight of the extract

in g

TPC can be calculated using the formula

C (GAE)=c X V/M

where, c-concentration determined from the standard curve(mg/ml)

V= Volume used during the assay

M= mass of the extract used during the assay (g).

The amount that you are going to get using the formula will give you TPC in mg/g

Hi, I have actually the same problem. I have my calibration curve (0.0121x + 0.0298) and the concentration of my sample (0.005 mg of cranberries/mg of cellulose), so I calculate the absorption. The result is 0.503152... but what is this result exactly? I don't understand what calcul I have to do after this to obtain the Total Phenolic Content.. Thanks for your help!

 Violeta Niculescu

The following finding of yours seems to have an error of unit? Please re-check.

160 g GAE/mL

For calibration curve of gallic acid, the serial dilutions are generally taken in the units of microgram per mL (or mg/L).

Margaux Léonard,

Please clearly explain what do you want to calculate? It is not clear from your description.

Hello Dildar Ahmed,

I want to calculate the total phenolic content in GAE/g of sample, but i don't know how to do because of the units

Hi, 

can somebody plz help me to calculate the gallic acid equivalents (mg/g). i have used 100 ul of 1mg/ml of plant extract.  to this i added 3ml water+ 0.5 ml fc reagent. after incubation  (3min), 2ml of 20% Na2Co3 was added. absorbance was noted at 650nm after 1hr. OD was 0.461. From the standard curve equation was y=0.1731x  R2= 0.9835 . can somebody plz help me with the calculation of gallic acid equivalents in mg/g

There are a number of ways to do this calculation. One simple way is this: The concentration of the plant extract used in the assay: x mg/mL. So, 1 mL contain = x mg; therefore,1000 mL or 1 L will contain= 1000x mg or (1000x)/1000 g = z g. Let this be your equation A.

Now, from the Gallic acid calibration, we get y microgram GAE per mL or y mg per L. Therefore, 1 L contains = y mg. Let this be your equation B.

Now, compare equation A with equation B. Thus, z g of the plant extract has = y mg GAE, that is y mg GAE per z g.

What about per 100 g?

z g has = y mg GAE,

Therefore, 1 g will have = y mg GAE/z g

So, 100 g will have = (y mg GAE/z g) 100 

I hope this simple method will help you and other friends to calculate TPC in the units of mg GAE per 100 g of extract.

In a similar way, we can calculate TFC in terms of mg Rutin equivalent per 100 g extract.

This articles can be useful as well. Find the attached

Hey guys, I wanna ask about my TPC (Total Phenolic Contain) calculation.

Here's what I've done

I've maserated 200g of fresh pomelo with 200 mL ethanol, then I've got my crude extract from rotary evaporation process.

I took 50 mg crude extract and diluted it with 5 mL of ethanol.

The next thing, I took 1 mL to test the TPC content.

Then I recieved my standard equation

Y= 0.001x + 0.061, with 0.082 absorbance. So I got x= 21 mg GAE/L.

Here's the question, have I done it right with this calculation 21 * 0.005L/ 0.05 g = 2.1 mg GAE/g extract?

And is it possible for me to convert it to mg GAE/ g fresh weight and mg GAE/ g dry weight (cause I've read a lot of literatures using those unit)

Thank you

Dear Veny,

Yes, you are doing well, and you must change the volume and the mass to get the concentration for the dry weight.

Please help me out to calculate my phenoloc content

I have taken 5gm powdered sample in 150 ml methanol and then evaporate it..

Then i take 10mg crude extract in 10ml methanol.(1mg/ml) and for the analysis 120microltr i take in testube and makeit upto 1ml with methanol.

After experiment i got the equation from graph is

Y=0.0162x+0.0817

And from the equation i got 12.83 ,then what will be the unit of this ,mg/ml or microgram/ml.

And how i will calculate as mgGAE/g