Hi Magda

The first question: mg GAE /g of the extract is not equal to mg GAE / g dry weight and you can not say that 160.38 mg GA / g extract is equal to 160.38 mg GA / g dry weight.

Yes, it is possible to transform a value from mg GA / g extract to mg GA / g dry weight.

To convert units to each other, you need to know about extraction yield (% yield)

Yield (%) = (Dry weight of extract ÷ Dry weight of plant material) × 100

you need to know how much dry weight of plant material is used for extraction, and how much dry extract is obtained.

If you read that article again, you will probably get the information you need (how much dry weight of plant material is used for extraction, and how much dry extract is obtained). With this information, I can help you to convert mg GA / g extract to mg GA / g dry weight.

Of course there is a difference between GAE/g (or 100 g) extract and GAE/g (or 100 g) dry weight of sample. You know that we can obtain the extract from a dry plant generally (or fresh plant in some cases). So, during the calculation of the content of phenolic content, we can refer the results obtained from the calibration curve of gallic acid to the dry weight of the extract used in the assay or to the dry weight of the original sample. To convert the results from GAE/g dry extract to GAE/g dry weight of sample, we need to know the yield of the extraction method used. It means that how much mg of extract could be obtained from 1 g of plant sample.

I agree with the reviewer about that the value of 16038 mg GAE/100 g extract is high. But if this value was for 100 g dry weight of sample there is no problem.

Greetings! As mentioned above, you need to know the yield of the extraction.

Also you can change the extraction methodology to ensure that you are extracting phenols as possible. For example, you perform three extractions with ethanol, evaporate the solvent in vacuo, and reconstitute to a known volume.

You must record all the amounts you use to calculate what you need.

Dear Marziye Rahimi Rizi and dear all,

Thanks for taking the time to answer my question.

I have searched in the whole paper the "extraction yield" term. I could not find such terminology, but according to the methodology, this is what they did:

The plant was freeze-dried and ground to a powder. The powder was dissolved in Ethanol, and the extract was filtered and concentrated using a vacuum evaporator. One milligram of the dried powder dissolved in 1 mL of ethanol was used for the experiments (they performed a DPPH assay and SOD-like activity).

Specifically for measuring the total phenolic content, they used the Folin–Ciocalteu method as follows: the reaction mixture containing 100 mL of the crude ethanol extract (1 mg/mL) was mixed with distilled water to a final volume of 3 mL. To this, 0.5 mL of Folin–Ciocalteu reagent was added and the mixture was allowed to stand for 3 min; 2 mL of 20% (w/v) sodium carbonate was then

added to this mixture. Following incubation for 1 h in the dark, the absorbance was measured at 760 nm using a spectrophotometer. Gallic acid at different

concentrations (20–100 μg/mL) was used as a standard.

This is all the information I have from the paper. As I mentioned, since I am not an expert on the field, I am not sure if this is the information you require, but I hope it can help you Marziye, to do the calculations. Thanks again in advance.

Magda

Dear Mahda,

By the cited procedure you can calculate the total phenolic content as mg GAE/g (or 100g) dry extract ONLY because the extraction yield was not provided.

Dear Magda

Sorry, it is not possible to convert mg GA / g extract to mg GA / g dry weight with the mentioned information. For more assurance, I can take a look at that article

Dear Duried Alwazeer and dear Marziye Rahimi Rizi

Thank you so much to both of you for your time and help. I can see where the problem goes... There is a lack of information in the article and the responses you are giving me are quite clarifying for me. I think the right procedure would be not to include the results of this article among those that I can express in mg GAE / 100 g dry weight.

Magda Gamba, yes it is a good idea not to include this article.

Dear Gamba

Please think it simply

My first question is: are mg GAE /g of extract equal or the same as mg GAE / g dry weight? could I just simply say that 160.38 mg GA / g extract are equal to 160.38 mg GA / g dry weight?

Ans: First you have to think your sample dry or live. If it is dry, than you can write 160.38 mg GA / g dry weight.

My second question if the above is false: Could it be that the author make an error either in describing the units in the methodology or in the results section?

Ans: May be author mistake or mention any one part of the article their sample was dry or live, if research methodology mention sample dry or live.............than we write mg GAE /g

Third question: if there is no mistake, is it possible to transform a value from mg GA / g extract to mg GA / g dry weight?

Ans: No transform each other

Thank you

Dear Md. Atikul Islam

Thanks for your reply. I did not transform any values mentioned in the article as it was not possible due to lack of information. In the meantime, my review has already been accepted for publication.

Dear Gamba

Good sound for me

Congratulations

Dear Md. Atikul Islam I have a question. You said "First you have to think your sample dry or live. If it is dry, than you can write 160.38 mg GA / g dry weight.", and well, I´m working with microalgae, and I only dried the biomass before the extraction, so I didn´t dried the extract. Could I express my results like mg GAE / g dry weight If I use a formula where I have to use the mass of extract? or could I only replace in this place the weight of my biomass?