A Comparative Analysis of Polyphenol Content and Biological Potential of Quercus petraea Matt. and Q. pubescens Willd. Bark Extracts

Round 1

Reviewer 1 Report

 

Dear editor:

Thank you very much for inviting me to review the MS. The MS “A Comparative Analysis of Polyphenol content and Biological Potential of Quercus petraea and Q. pubescens Bark Extracts” is interesting and is well presented. But it needs minor revision. Therefore I recommend that The MS is minor revision.

The follows are some suggestion on revising the MS.

Line 37 -38: Moreover, the effect on the bacterial DNA, of the most efficient experimental variants, was tested using the comet assay. Not clear, please modified. In this article no description about comet assay. Add comet assay method and show result. Also modify result and discussion.

Line 63: Please add more information about “health benefits”.

Lines 74-76: “Pseudomonas aeruginosa, Bacillus cereus, Listeria monocytogenes, 74 Escherichia coli, Mycobacterium flavus and Staphylococcus aureus and various fungal strains 75 from the Aspergillus, Candida and Penicillium genus”. Please add relevant references.

Lines 81-84: Add more information about antifungal, cytotoxic, and enzyme inhibitory activity with proper updated references.

Line 95: The protocols used for the assessment of total tannin content and antioxidant activity” for protocols please add references.

Line 128: Extracts obtained using both methods were then filtered through regular filter paper under vacuum. Please mention filter paper size.

Fig 1 and Fig 2 need (a), (b) mark.

Figure legends: All figure legends were very poorly written. Need serious revision.

Line 307: IC50 should IC₅₀. Check all (L – 398, 400, ………….)

 Lines 314-316: Drozdz et al. showed that ethanolic extracts obtained from the bark of Q. robur had a higher antioxidant capacity 315 than butylated hydroxytoluene (a common antioxidant food additive) [30]. Please rewrite.

Line 342: “Valencia-Aviles et al. [32] did not only show the inhibitory effect of 342 Q. crassifolia bark extracts against E. coli but also showed this effect was selective.” Please rewrite. Sentence started with XXXX et al not good fit anywhere. Carefully check everywhere.

Line 346: The extracts obtained from the bark of Q. ilex by Berahou et al. [33] exhibited moderate…. Rewrite like “The extracts obtained from the bark of Q. ilex exhibited moderate….[33]”. Pls add relevant references.

Author Response

Dear reviewer,

First of all, thank you for the professional comments and observations. We thank for comments, which have made us think carefully about our data sets again. Accordingly, we have reanalysed these where necessary. Please find below our point-by-point itemized answer and correction. We write to say that we now strongly believe that we can convince you that the data is sound and that we have adequately answered in various valid concerns.

Response to reviewer 1

1. Line 37 -38: Moreover, the effect on the bacterial DNA, of the most efficient experimental variants, was tested using the comet assay. Not clear, please modified. In this article no description about comet assay. Add comet assay method and show result. Also modify result and discussion.

 

Author’s response: Thank you for the observation! The results of the DNA damage assay were not concluding, thus we decided to not add them in the final form of the draft. We removed the sentence from the abstract.          

 

2. Line 63: Please add more information about “health benefits”.

 

Author’s response: Thank you for the comment! We added specific health benefits of the bark extracts: “The beneficial effects of oak bark extracts include anti-inflammatory [6,7], antitumoral/antiproliferative [8], antidiabetic/hypoglycaemic [9], hypocholesterolemic [10], antihypertensive [11] and antimicrobial [12] activities.”

 

3. Lines 74-76: “Pseudomonas aeruginosa, Bacillus cereus, Listeria monocytogenes, 74 Escherichia coli, Mycobacterium flavus and Staphylococcus aureus and various fungal strains 75 from the Aspergillus, Candida and Penicillium genus”. Please add relevant references.

Author’s response: Thank you! We added more relevant references.

 

4. Lines 81-84: Add more information about antifungal, cytotoxic, and enzyme inhibitory activity with proper updated references.

 

Author’s response: Thank you for your comment! We extended our introduction with more information regarding the biological effects and the link between these effects and the polyphenolic compounds: “indicating that gallic acid and catechin are the main antiproliferative components of the bark extracts [8]. The correlation between the content in antioxidant compounds like catechin and epicatechin and the cytotoxic effects of oak bark extracts was also highlighted against breast cancer (MDA-MB-231) and cervical cancer (HeLa) cell lines [20].”, “The inhibitory effects of the extracts against α-glucosidase and tyrosinase were linked to two polyphenolic compounds, namely chlorocatechin and polydatin (a glucoside of resveratrol), the latter one being an extremely potent tyrosinase inhibitor, as an isolated compound [9].”

 

5. Line 95: The protocols used for the assessment of total tannin content and antioxidant activity” for protocols please add references.

 

Author’s response: Thank you! The references were added in section 2.4 and 2.5.

  

6. Line 128: Extracts obtained using both methods were then filtered through regular filter paper under vacuum. Please mention filter paper size.

 

Author’s response: Thank you for the comment! We added the pore sizes of the filter paper: “(pore size of 20µm)”  

 

7. Fig 1 and Fig 2 need (a), (b) mark. Figure legends: All figure legends were very poorly written. Need serious revision.

 

Author’s response: Thank you for the observation! We improved the descriptions in the legends of the figures and tables.  

 

8. Line 307: IC50 should IC₅₀. Check all (L – 398, 400, ………….)

 

Author’s response: Thank you for the comment! We changed the notation of the “50” for subscript.

 

9. Lines 314-316: Drozdz et al. showed that ethanolic extracts obtained from the bark of Q. robur had a higher antioxidant capacity 315 than butylated hydroxytoluene (a common antioxidant food additive) [30]. Please rewrite. Line 342: “Valencia-Aviles et al. [32] did not only show the inhibitory effect of 342 Q. crassifolia bark extracts against E. coli but also showed this effect was selective.” Please rewrite. Sentence started with XXXX et al not good fit anywhere. Carefully check everywhere. Line 346: The extracts obtained from the bark of Q. ilex by Berahou et al. [33] exhibited moderate…. Rewrite like “The extracts obtained from the bark of Q. ilex exhibited moderate….[33]”. Pls add relevant references.

 

Author’s response: Thank you for the comments! A different formulation was used for the sentences in the discussions. Also, the correct reference was added for the line 346.

Reviewer 2 Report

The research investigated the phytochemical profile of Q. petraea and Q. pubescens bark extracts, the evaluation the biological potential of these extracts as antioxidant, antibacterial, antifungal, cytotoxic, and enzyme inhibitory agents. The research idea is good but the manuscript needs some modifications:

 

-   Introduction part is brief; it needs some new information and references.

-         In the materials and methods part:

1.     In the quantification of Total Phenolics; the standard material and their concentrations that are included in the standard curve need to add to the method.

2.     In the quantification of Tannins; authors should illustrate the method not in brief and mention the standard material and their concentration that is included in the standard curve.

3.   In the assay of the Antimicrobial Activity; what is the bacterial inoculum concentration?

4.     In the evaluation of cytotoxicity; what is the source of the kidney cells?

 -         In the result part: in the figures, all the letters above columns need to be in italics.

The authors need to follow the reference style of the journal.

The manuscript needs English language and grammar revision.

Author Response

Dear reviewer,

First of all, thank you for the professional comments and observations. We thank for comments, which have made us think carefully about our data sets again. Accordingly, we have reanalyzed these where necessary. Please find below our point-by-point itemized answer and correction. We write to say that we now strongly believe that we can convince you that the data is sound and that we have adequately answered in various valid concerns.

Response to reviewer 2:

 

1. Introduction partis brief; it needs some new information and references.

 

Author’s response: Thank you for the comment! We added more information and also more references.

 

2. In the quantification of Total Phenolics; the standard material and their concentrations that are included in the standard curve need to add to the method.

 

Author’s response: Thank you for your comment! We added the required information in the methods section: “For the quantification of the phenolic content, a standard curve made of nine different gallic acid solutions was used. The concentrations ranged from 0.05 mg/mL to 0.45 mg/mL. The linear equation of the curve is y = 11.767*x + 0.2737.”

 

3. In the quantification of Tannins; authors should illustrate the method not in brief and mention the standard material and their concentration that is included in the standard curve.

 

Author’s response: Thank you for the observation! We did not consider detailing the tannin content method as it is a pharmacopeial method, thus being better described in the original source. The method did not use a standard curve, only an external standard as described in the pharmacopeia. We added the next phrase in the method section for total tannin content: “For the quantification of the total tannin content an external standard of pyrogallol was used. This standard solution had a concentration of 0.025 mg/mL as described in the pharmacopeial method.”

 

4. In the assay of the Antimicrobial Activity; what is the bacterial inoculum concentration?

 

Author’s response: Thank you for the comment! The bacterial inoculum used had a turbidity of 0.5 McFarland as we already mentioned in the draft. We did not measure the bacterial inoculum concentration in any other way.  

 

5. In the evaluation of cytotoxicity; what is the source of the kidney cells?

 

Author’s response: Thank you for the observation! We added the source of the kidney cells: “The HEK 293T cells were obtained from the Institute of Experimental Virology, UZH, Zürich.”

 

6. In the result part: in the figures, all the letters above columns need to be in italics.

 

Author’s response: Thank you for the observation! All the figures were changed accordingly.

 

7. The authors need to follow the reference style of the journal.

 

Author’s response: Thank you! We followed the reference style of the journal and we have also done minor changes to better suit the journal style.

 

8. The manuscript needs English language and grammar revision.

 

Author’s response: Thank you! We revised the English language and grammar.

 

Round 2

Reviewer 2 Report

The authors did a great job of improving the manuscript quality and I recommended accepting it.

Author Response

Dear reviewer, 

Thank you for accepting our manuscript!