Impact of the Season on Total Polyphenol and Antioxidant Properties of Tea Cultivars of Industrial Importance in Northeast India

Round 1

Reviewer 1 Report

This manuscript is about impact of season on total polyphenol and antioxidant properties of tea cultivars of industrial importance in Northeast India. It is interesting and I think, a minor revision of manuscript is needed.  You can find my comments in below:

1. The manuscript must be revised grammatically and the English level of it must be improved by a native editor.

2. The authors must re-write the abstract and conclusion sections. I think some sentences are not needed to be in these sections.

3. In introduction section (after references 3-6), please give detail about flavonols, phenolic acids and anthocyanins.

4. In introduction section, please add more references about the same researches which worked on current research title.

5. In section 2.6, it is not acceptable to use same references for every experiment. The authors use Deka et al. 2021 for section 2.5. So, please add another reference: https://doi.org/10.1111/jfpp.15774.

6. Please re-write section 2.10 which is about statistical analysis.

7. In results and discussion section, please give more references and write more details. The authors must compare their results with the results of previous researches.

8. Please increase the DPI values of figures. The quality of them is poor. Also, please make the tables more desirable. They are not looking that much good.   

The manuscript must be revised grammatically and the English level of it must be improved by a native editor.

Author Response

Reviewer 1

This manuscript is about impact of season on total polyphenol and antioxidant properties of tea cultivars of industrial importance in Northeast India. It is interesting and I think, a minor revision of manuscript is needed.  You can find my comments in below:

Comment 1. The manuscript must be revised grammatically and the English level of it must be improved by a native editor.

Reply:  Thank you very much for your suggestions for the improvement of the manuscript. The manuscript has been thoroughly checked and revised to correct grammatical mistakes. A native speaker has made a few changes to improve the English language.

Comment 2. The authors must re-write the abstract and conclusion sections. I think some sentences are not needed to be in these sections.

Reply: The abstract and conclusion have been thoroughly revised.

Comment 3. In introduction section (after references 3-6), please give detail about flavonols, phenolic acids and anthocyanins.

Reply: The details about flavonols, phenolic acids, and anthocyanins have been in the introduction (Pages no. 1-2).

Comment 4. In introduction section, please add more references about the same researches which worked on current research title.

Reply: Thank you very much for the suggestion. Few more references related to the current research have been added in the introduction section (Page no. 2).

Comment 5. In section 2.6, it is not acceptable to use same references for every experiment. The authors use Deka et al. 2021 for section 2.5. So, please add another reference: https://doi.org/10.1111/jfpp.15774.

Reply: The reference Niknam et al., 2021 has been incorporated as suggested.

Comment 6. Please re-write section 2.10 which is about statistical analysis.

Reply: Section 2.10 has been rewritten.

Comment 7. In results and discussion section, please give more references and write more details. The authors must compare their results with the results of previous researches.

Reply: Thank you for your valuable comments on the improvement of the manuscript. We have tried to add some more related references to the discussion section. However, it is very difficult to directly compare the current findings with those reported by other researchers as the biochemical contents vary with cultivar, climatic conditions of the growing regions, agricultural practices, manufacturing processes, etc. Moreover, the extraction procedure and solvent used for antioxidant activity measurements also affect the results. The cultivars reported in this manuscript are primarily developed by TTRI and planted in the north-eastern region of India and this is the first study of such kind.

Comment 8. Please increase the DPI values of figures. The quality of them is poor. Also, please make the tables more desirable. They are not looking that much good.   

Reply: The quality of figures (DPI values) and tables have been improved.

Reviewer 2 Report

Deka et al. have conducted a comprehensive study on the "Impact of season on total polyphenol and antioxidant properties of tea cultivars of industrial importance in Northeast India". The study design and corresponding analyses are robust, and the data demonstrates the positive effect of the monsoon season on the antioxidant activity of various cultivars. However, the manuscript can be improved by implementing the following recommended changes (both minor and major):

-        Abstract, Line 7: Replace the semicolon before "respectively" with a comma for improved clarity.

-        Throughout the paper, the abbreviation "TP" has been used for "total polyphenol content". However, this abbreviation might be confusing in certain contexts. Therefore, I recommend replacing it with either "TPC" (total polyphenol content) or "TPs" (total polyphenols) to enhance readability and consistency.

-        In Section 2.4, please clarify that the method used was indeed the Folin-Ciocalteu method.

-        Regarding the presentation of results (Figures 1-3), it is not explicitly stated whether the researchers measured the concentration of different catechins and if so, the method used for measurement (e.g., HPLC). For clarity, please provide more information about the plotting of Heatmaps in the Methods section.

-        To provide readers with a broader perspective, consider adding a sentence or two about the future directions of this study at the end of the conclusion. This addition would offer insights into potential areas for further research and exploration in this field.

There are minor editions required. Overall, I recommend proofreading of the whole manuscript before submission of the revision. 

Author Response

Reviewer 2

Deka et al. have conducted a comprehensive study on the "Impact of season on total polyphenol and antioxidant properties of tea cultivars of industrial importance in Northeast India". The study design and corresponding analyses are robust, and the data demonstrates the positive effect of the monsoon season on the antioxidant activity of various cultivars. However, the manuscript can be improved by implementing the following recommended changes (both minor and major):

Comment 1. Abstract, Line 7: Replace the semicolon before "respectively" with a comma for improved clarity.

Reply: Thank you very much for your insightful observations and comments. All the semicolons before "respectively" have been replaced with a comma.

Comment 2. Throughout the paper, the abbreviation "TP" has been used for "total polyphenol content". However, this abbreviation might be confusing in certain contexts. Therefore, I recommend replacing it with either "TPC" (total polyphenol content) or "TPs" (total polyphenols) to enhance readability and consistency.

Reply: The manuscript has been thoroughly checked. The term “total polyphenol” has been abbreviated as “TP” and now “total polyphenol content” appears as “TP content”.

Comment 3. In Section 2.4, please clarify that the method used was indeed the Folin-Ciocalteu method.

Reply: The recommended change has been made in the revised manuscript.

Comment 4. Regarding the presentation of results (Figures 1-3), it is not explicitly stated whether the researchers measured the concentration of different catechins and if so, the method used for measurement (e.g., HPLC). For clarity, please provide more information about the plotting of Heatmaps in the Methods section.

Reply: The data on catechins and caffeine was adopted from our previous publication in the Journal of Food Composition and Analysis (https://doi.org/10.1016/j.jfca.2020.103684) wherein all the methods related to extraction and determination of these compounds have been reported in detail. This has been mentioned in this manuscript, in the last part of the introduction section (Page no. 2).

Comment 5. To provide readers with a broader perspective, consider adding a sentence or two about the future directions of this study at the end of the conclusion. This addition would offer insights into potential areas for further research and exploration in this field.

Reply: A few words regarding the use of the findings of the work to produce better quality tea have been incorporated in the conclusion. However, detailed studies need to be carried out.

Reviewer 3 Report

It is an interesting research paper about the “Impact of season on total polyphenol and antioxidant properties of tea cultivars of industrial importance in Northeast India” The article explored the impact of season on total polyphenol content (TP) and the antioxidant activity of thirty-one TV cultivars (TV1-TV31) and four other commercially popular cultivars; namely; Betjan; Kharijan; S.3A/3; and T.3E/3. This article contains some issues in results and discussion and needs to be improved.

The authors presented the results for catechins and caffeine contents but what was the methodology used for their extraction and determination?  In the section 2, it should introduce the preparation of tea extract and the methodology used

Section 3. Results and discussion

3.2.2. ABTS scavenging activity

Explain better this sentence: “The activity of cultivar TV1 was significantly different (p ≤ 0.01) from all others except TV11 and TV29 which had similar levels.”  But in table the TV1 and TV11 has the letter (a) and TV29 has another letter (b), probably it must be letter (a), according to the results

3.2.3. Ferric reducing antioxidant potential

The sentence: “FRAP of cultivars varied from 5144.38 mM Fe²⁺ g^-1 in TV26 to 8973.19 mM Fe²⁺ g^-1 in TV1, expressing a 74% variation between the highest and lowest ranked cultivars (Table 4).” According to table 4 the lowest values was in TV27 (4912.36±67.27).

3.2.4. Lipid peroxidation inhibition activity

The sentence: “In pre-monsoon, LPI activity ranged from 58.65% in TV8 to 78.92% in TV3 (Table 5)”. According to table 5 the lowest value was in TV9 (51.25±4.62).

The sentence: “The cultivars TV2, TV4, TV12, TV20, TV29 and Betjan also exhibited similar levels of activity.” See better the results

The sentence: “In autumn, cultivar TV9 exhibited the highest LPI activity at 71.39% whereas TV27 exhibited the lowest activity at 64.06%.” According to table 5 the lowest value was in TV26 (56.85±1.02)

See better the results of discussion referred in Fig 2 and 3

Author Response

Reviewer 3

It is an interesting research paper about the “Impact of season on total polyphenol and antioxidant properties of tea cultivars of industrial importance in Northeast India” The article explored the impact of season on total polyphenol content (TP) and the antioxidant activity of thirty-one TV cultivars (TV1-TV31) and four other commercially popular cultivars; namely; Betjan; Kharijan; S.3A/3; and T.3E/3. This article contains some issues in results and discussion and needs to be improved.

Comment 1. The authors presented the results for catechins and caffeine contents but what was the methodology used for their extraction and determination?  In the section 2, it should introduce the preparation of tea extract and the methodology used

Reply: Thank you for your insightful observations and suggestions.

The data on catechins and caffeine was adopted from our previous publication in the Journal of Food Composition and Analysis (https://doi.org/10.1016/j.jfca.2020.103684) wherein all the methods related to extraction and determination of these compounds have been reported in detail. This has been mentioned in this manuscript, in the last part of the introduction section (Page no. 2).

Comment 2. Section 3. Results and discussion

3.2.2. ABTS scavenging activity

Explain better this sentence: “The activity of cultivar TV1 was significantly different (p ≤ 0.01) from all others except TV11 and TV29 which had similar levels.”  But in table the TV1 and TV11 has the letter (a) and TV29 has another letter (b), probably it must be letter (a), according to the results

Reply: We greatly appreciate your observations. We have rechecked the statistical data and it is confirmed that TV29 has the letter (b). Therefore, we have removed TV29 from the statement in the revised manuscript. Now it appears as “The activity of cultivar TV1 was significantly different (p ≤ 0.01) from all others except TV11 which had a similar level.” 

Comment 3. 3.2.3. Ferric reducing antioxidant potential

The sentence: “FRAP of cultivars varied from 5144.38 mM Fe²⁺ g^-1 in TV26 to 8973.19 mM Fe²⁺ g^-1 in TV1, expressing a 74% variation between the highest and lowest ranked cultivars (Table 4).” According to table 4 the lowest values was in TV27 (4912.36±67.27).

Reply: The corrections have been made in the revised manuscript. The revised sentence appears as “FRAP of cultivars varied from 4912.36 mM Fe²⁺ g^-1 in TV27 to 8973.19 mM Fe²⁺ g^-1 in TV1, expressing a 82% variation between the highest and lowest ranked cultivars (Table 4)”.

Comment 4. 3.2.4. Lipid peroxidation inhibition activity

 The sentence: “In pre-monsoon, LPI activity ranged from 58.65% in TV8 to 78.92% in TV3 (Table 5)”. According to table 5 the lowest value was in TV9 (51.25±4.62).

Reply: The corrections have been made in the revised manuscript. The revised sentence appears as “In pre-monsoon, LPI activity ranged from 51.25% in TV9 to 78.92% in TV3 (Table 5)”.

Comment 5. The sentence: “The cultivars TV2, TV4, TV12, TV20, TV29 and Betjan also exhibited similar levels of activity.” See better the results

Reply: The corrections have been made in the revised version of the manuscript. Now it appears as “The cultivars TV2, TV29, and Betjan also exhibited similar levels of activity as that of TV3”.

Comment 6. The sentence: “In autumn, cultivar TV9 exhibited the highest LPI activity at 71.39% whereas TV27 exhibited the lowest activity at 64.06%.” According to table 5 the lowest value was in TV26 (56.85±1.02)

Reply: The corrections have been made in the revised version of the manuscript. Now it appears as “In autumn, cultivar TV9 exhibited the highest LPI activity at 71.39% whereas TV26 exhibited the lowest activity at 56.85%.”

Comment 7. See better the results of discussion referred in Fig 2 and 3

Reply: We have gone through the correlation heatmaps (Figures 2 and 3). A few corrections were needed there, and we change in the discussion accordingly.

Reviewer 4 Report

General comment

The manuscript ''Impact of season on total polyphenol and antioxidant properties of tea cultivars of industrial importance in Northeast India'' described the content of total polyphenol content  and the antioxidant activity (evaluated using DPPH, ABTS, FRAP, and LPI) of thirty-one Tocklai vegetative cultivars and four other cultivars. It was found significant positive correlation of antioxidant activity with TP content (R2 ranging from 0.83 to 0.96). It is interesting that the total polyphenol content was higher in monsoon season than in pre-monsoon and autumn.

Minor comments

Abstract

I supose that Tocklai vegetative cultivars are cultivars of Camellia sinensis (L.) O. Kuntze. Please, add it somewhere in both section Abstract and Introduction.

It is not clear what means g-1 in mg per g-1? Grams of dry plant material?

2. Materials and Methods

2.1. Chemicals

Add town and state after ''Sigma-Aldrich''

Add town and state after ''HiMedia''

Add town and state after ''MERCK''

Change ''ciocalteu'' into ''Ciocalteu''

2.2. Instrumentation

Add town and state after ''Cary 50''

Merck or MERCK? It should be written on the same way.

Add town and state after ''Eutech Instru ments''

2.3. Tea leaf sampling

Page 3: Change short hyphnen in symbol minus before ''80''

2.4. Determination of total polyphenol

Line 4: change ''ml'' into ''mL'' after ''10''

Line 8: change ''hr'' into ''h'' or ''hour'' (hr is not SI unit)

2.5. Preparation of tea extracts for antioxidant activity study

Line 5: ''ml'' into ''mL'' after ''25''

2.6. DPPH radical scavenging activity

Line 2: ''ml'' into ''mL'' after ''0.25''

Line 3: ''ml'' into ''mL'' after ''2.5''

2.7. ABTS radical scavenging activity

Line 4: change ''hrs'' into ''h'' or ''hour''

Line 8: change ''hr'' into ''h'' or ''hour''

2.8. Ferric Reducing Antioxidant Potential (FRAP) Assay

Last line: change ''FeSO4.7H2O'' into ''FeSO4 7H2O''

2.9. Lipid peroxidation inhibition assay

Line 7: change ''hr'' into ''h'' or ''hour''

3. Results and Discussion

Table 1, 2, 3, 4, 5: superscript denotes a significant difference at p ≤ 0.01 or p ≤ 0.05? Please, add.

References

The journal names should be written on the same way. So, use full name or journal abbreviation. Not both.

Ref. no 7, 24, 29: Put ''Camellia Sinensis'' in Italic and change ''Sinensis'' into ''sinensis''

Ref. no 15: add space before ''Content''

Ref. no. 18: omit one quotation mark in “‘Antioxidant Power’”

Ref. no 40: Put ''Ilex Paraguariensis'' in Italic and change ''Paraguariensis'' into ''Paraguariensis''

Author Response

Reviewer 4

General comment

The manuscript ''Impact of season on total polyphenol and antioxidant properties of tea cultivars of industrial importance in Northeast India'' described the content of total polyphenol content  and the antioxidant activity (evaluated using DPPH, ABTS, FRAP, and LPI) of thirty-one Tocklai vegetative cultivars and four other cultivars. It was found significant positive correlation of antioxidant activity with TP content (R2 ranging from 0.83 to 0.96). It is interesting that the total polyphenol content was higher in monsoon season than in pre-monsoon and autumn.

Reply: We thank you very much for your observations and comments.

Comment 1. Abstract

I supose that Tocklai vegetative cultivars are cultivars of Camellia sinensis (L.) O. Kuntze. Please, add it somewhere in both section Abstract and Introduction.

Reply: Thank you very much for your insightful observations. We have added “Camellia sinensis (L.) O. Kuntze” in the introduction section.

Comment 2. It is not clear what means g-1 in mg per g-1? Grams of dry plant material?

Reply: Here we mean the amount of a particular compound present in mg per gram of dry tea leaf.

Comment 3. 2. Materials and Methods

2.1. Chemicals

Add town and state after ''Sigma-Aldrich''

Add town and state after ''HiMedia''

Add town and state after ''MERCK''

Change ''ciocalteu'' into ''Ciocalteu''

Reply: Changes have been made in the revised manuscript.

Comment 4. 2.2. Instrumentation

Add town and state after ''Cary 50''

Merck or MERCK? It should be written on the same way.

Add town and state after ''Eutech Instru ments''

Reply: Changes have been made in the revised manuscript.

Comment 5. 2.3. Tea leaf sampling

Page 3: Change short hyphnen in symbol minus before ''80''

Reply: The necessary change has been made.

Comment 6. 2.4. Determination of total polyphenol

Line 4: change ''ml'' into ''mL'' after ''10''

Line 8: change ''hr'' into ''h'' or ''hour'' (hr is not SI unit)

Reply: The necessary changes have been made.

Comment 7. 2.5. Preparation of tea extracts for antioxidant activity study

Line 5: ''ml'' into ''mL'' after ''25''

Reply: The required change has been made.

Comment 8. 2.6. DPPH radical scavenging activity

Line 2: ''ml'' into ''mL'' after ''0.25''

Line 3: ''ml'' into ''mL'' after ''2.5''

Reply: The required change has been made.

Comment 9. 2.7. ABTS radical scavenging activity

Line 4: change ''hrs'' into ''h'' or ''hour''

Line 8: change ''hr'' into ''h'' or ''hour''

Reply: The necessary changes have been made.

Comment 10. 2.8. Ferric Reducing Antioxidant Potential (FRAP) Assay

Last line: change ''FeSO4.7H2O'' into ''FeSO4 7H2O''

Reply: The required change has been made.

Comment 11. 2.9. Lipid peroxidation inhibition assay

Line 7: change ''hr'' into ''h'' or ''hour''

Reply: The required change has been made.

Comment 12. 3. Results and Discussion

Table 1, 2, 3, 4, 5: superscript denotes a significant difference at p ≤ 0.01 or p ≤ 0.05? Please, add.

Reply: Different superscript denotes a significant difference at p ≤ 0.05. It is added below the tables in the revised manuscript.

Comment 13. References

The journal names should be written on the same way. So, use full name or journal abbreviation. Not both.

Ref. no 7, 24, 29: Put ''Camellia Sinensis'' in Italic and change ''Sinensis'' into ''sinensis''

Ref. no 15: add space before ''Content''

Ref. no. 18: omit one quotation mark in “‘Antioxidant Power’”

Ref. no 40: Put ''Ilex Paraguariensis'' in Italic and change ''Paraguariensis'' into ''Paraguariensis''

Reply: The suggested changes have been made in the revised manuscript.

Round 2

Reviewer 3 Report

The manuscript has been improved and suggestions accepted. The paper may be published in this form.