Question
Asked 20th Oct, 2017

How can I calculate the total phenolic content of my sample (Plant Extract)?

Can anyone help me step wise calculation for determination of total phenolic contents in Plant extracts?
Given the following:
5mg/50ml (5mg plant extract was dissolved in 50ml Methanol) and 300 ul (microliter) was taken for analysis.
Absorbance of sample at 760 nm = 0.541
Standards curve provided the following information: y=0.0109x- 0.022; R2  = 0.9995.
Thanks.

Most recent answer

Md. Tahjib-Ul-Arif
Bangladesh Agricultural University
How do you extract plant sample for phenolic compound determination? Would you please provide me the complete protocol of TPC determination?
1 Recommendation

All Answers (6)

Muhammad Mushtaq
Government College University, Lahore
It is quite simple, let me clarify you,
Just follow your calibration curve (is it in ug of gallic acid/mL), if so "x" would give you the microgram of gallic acid equivalent per ml of your solution, now multiply this with 50 (this give you microgram of TPC/5mg of your plant extract. Now just see an appropriate unit (may be mg/g of extract or ug/g of extract or others), One more thing if you want to express your result per gram of plant powder the above answer with yield and divide by amount of plant material processed. Best of luck.
for further consultation
DOI: 10.1007/s13197-014-1562-9
1 Recommendation
Dear Sir. Concerning your issue about the calculation for the determination of the total phenolic content (TPC) in Plant Extract.
First you need to use equation y=0.0109x- 0.022 to calculate the value of x
Where y = Absorbance
x = concentration from the calibration curve
This implies that x = 0.541 + 0.022/0.0109
x = 51.65 mg/mL
Therefore, TPC can be calculated as follows
TPC = cV/m
Where c= concentration from calibration curve
V= Volume of the extract used
m= Mass of the extract used
Therefore, TPC = cV/m
TPC = 51.65x50/5.0
TPC = 516.5 mg /g
May I know the type of standard and its concentration. I think the following below links may help you in your analysis:
Thanks

2 Recommendations
Hammad Saleem
University of Veterinary and Animal Sciences
I use Gallic acid(5mg/50ml) as standard.
Thnansk.
Dear Hammad Saleem
So according to the mentioned above the answer should be:
TPC = 516.5 mgGAE/g
Regards,
Muhammad Mushtaq
Government College University, Lahore
Dear Hammad Salem and Isam Eldin
Let me clarify one more thing you cannot estimate phenolic content following a single concentration of gallic acid as you are discussing here. In fact you have plotted a calibration curve so the unit of "X" would be as same as were present on the x-axis it may be mg/mL or ug/mL so having clear understanding is more important for correct calculation. Otherwise like many people do you may get 1025 mg GAE/g (A none sense) in an other sample. may be you have already faced same. I just mean to say double check and follow you calibration curve
Md. Tahjib-Ul-Arif
Bangladesh Agricultural University
How do you extract plant sample for phenolic compound determination? Would you please provide me the complete protocol of TPC determination?
1 Recommendation

Similar questions and discussions

How to build Gallic Acid Curve and calculate Total Phenolic Content?
Question
15 answers
  • Piedad ParejaPiedad Pareja
Hello, researchers! I hope you can help me solving this doubt. First I will briefly explain to you what I did in the lab work and how I calculated TPC:
1. Preparation of Galic Acid solutions: 5 solutions were prepared with the following concentrations: 3g/l; 2.1 g/L; 1.5g/L; 0.9g/L and 0.3g/L
2. Preparation of my sample: 0.25g of sample was mixed with 5 ml of methanol 
3. Reaction with Folin-Ciocalteu solution: 
 - I add 0.5 ml of my clear extract in a 50 ml flask.
- I added 2.5 ml of FCR, 7.5 ml of a Sodium carbonate solution (200g NACO3 in 1 L water) and brought the volume to 50 ml with distilled water.
- I followed this procedure for both my standard (Gallic Acid solution) and my sample.  
- The absorbance was read at 760 nm
4. I built the standard curve: using the concentrations of 0.3-3 g/L
5. Using the standard curve I got a concentration of 0.042 g/L
5. I calculated TPC with the following equation: 
TPC= C x DF x V / m 
C: Concentration of Gallic Acid (calculated with the standard curve)
DF: Dilution factor
V: Volume extract
m: weight of the sample
6. Finally,  I got a TPC of around 8580mg/100 g 
QUESTION??
I have some doubts about my results because they seem to be very high in comparison with some literature reviewed. My doubt is about the Gallic Acid Curve. I built it using the initial concentrations that I prepared (0.3g/L-3g/L) and the absorbance read in the spectrophotometer. However, as I did with my sample, the standard solution was also diluted in the 50 ml flask. Thus, what the spectrophotometer really read was a diluted solution right? 
Tha means that I have to include also this dilution factor for my standard curve? Instead of building my curve with the initial concentration (0.3g/L-3g/L), should I build it with the diluted ones (0.003g/l-0.03g/L)? 
Thank you for your help!!! :)

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