Biological Activity of Root Extract Decalepis hamiltonii (Wight & Arn) against Three Mosquito Vectors and Their Non-Toxicity against the Mosquito Predators
, Rengarajan Manivasagaperumal 3 and Patcharin Krutmuang 4,5,*Round 1
Reviewer 1 Report
The authors of this manuscript describe mosquito larvicidal activity of D. Hamiltonii methanol extracts.
Many studies have shown that a methanol extract from roots or seeds, possessed high larvicidal activity toward many mosquito spp. But methanol and ethanol are universal solvents in solvent extraction for phytochemical natural products such as flavonoids, polyphenols, carotenoids, alkaloids, steroids, fatty acids, …….. and generally, a column chromatography should be employed for separation and fraction of different compounds in the crude extract.
While I appreciate the effort the authors have made to gather their data and I understand the intentions of their work, but the main problems of the paper is that, in my opinion, we are not sure that the fatty acids are the main components of the methanol extracts, since many of the rest of the components are non volatile and therefore cannot be separated and identified by GC-MS.
Literature review presented about mosquito’s larvicidal activity is insufficient; there are many studies which addressed.
Besides that, there are critical questions and corrections before the manuscript should be accepted for publications.
The issues that need to be addressed are listed below:
- The Title: The title is inappropriate, mainly because we are not sure that stearic acid and oleic acid are their “chief derivatives”
- The abstract: The GC-MS analysis of methanol extracts showed six major peak constituents represent the 117,9 % of the total composition….
- The Material and methods. Weak information or is not clear. Definitely, the material and methods section has to be rewritten again. It is very important to specify more information about:
- Chemicals: They have not used pure standards?
- Plant preparation: Roots were pulverized….. or they were extracted without any previous processing
- Soxhlet extraction: The yield from different extract (chloroform, ethyl acetate,….) were……. The extract was dried over anhydrous…..
- GC-MS analysis …The HP5 column is not optimal for fatty acid analysis…. Do you? The authors should explain in more detail about the components identification
- The larvicidal bioassay methodology is crucial in the manuscript: It would be interesting to include more information
- Larvicidal activity ….. Page 4, line 1 : “The GC-MS results……”
- Inappropriate data analysis and also inconsistent with the results presented
- The table 1 is not presented clearly; especially because it has a difficult reading and there are significant structure mistakes (9,10-octadecadienoic …. Z or E? )
- It really seems to not much care was taken to reliably identify compounds and rather just run a library search, which is bad practice.
- I don't really understand the results of the statistical analysis that has been done.
- Inaccurate conclusions on assumptions that are not supported by your data
Author Response
Reviewer-I
The authors of this manuscript describe mosquito larvicidal activity of D. Hamiltonii methanol extracts. Many studies have shown that a methanol extract from roots or seeds, possessed high larvicidal activity toward many mosquito spp. But methanol and ethanol are universal solvents in solvent extraction for phytochemical natural products such as flavonoids, polyphenols, carotenoids, alkaloids, steroids, fatty acids, ……..and generally, a column chromatography should be employed for separation and fraction of different compounds in the crude extract. While I appreciate the effort the authors have made to gather their data and I understand the intentions of their work, but the main problems of the paper is that, in my opinion, we are not sure that the fatty acids are the main components of the methanol extracts, since many of the rest of the components are non-volatile and therefore cannot be separated and identified by GC-MS.
Answer:-
We thank the reviewer for his valuable suggestion and feedback to our manuscript. As per the suggested comments all the corrections have been carried out throughout the manuscript.
Literature review presented about mosquito’s larvicidal activity is insufficient; there are many studies which addressed.
Answer:-
As per the reviewer suggestion, the literature review was revised in the manuscript.
Besides that, there are critical questions and corrections before the manuscript should be accepted for publications. The issues that need to be addressed are listed below:
Answer:-
As per the reviewers suggestions all the comments were taken seriously and revised properly in the manuscript.
- The Title: The title is inappropriate, mainly because we are not sure that stearic acid and oleic acid are their “chief derivatives”
Answer:-
We accept the reviewer comments and as per the suggestion the title of our research has been changed.
2. The abstract: The GC-MS analysis of methanol extracts showed six major peak constituents represent the 117,9 % of the total composition….
Answer:-
As for the reviewers concern, the peak area percentage was wrongly stated and it was rectified in the manuscript.
3. The Material and methods. Weak information or is not clear. Definitely, the material and methods section has to be rewritten again. It is very important to specify more information about:
Answer:-
As per the reviewer suggestion the methodology section was explained in detail.
4. Chemicals: They have not used pure standards?
Answer:-
As for the reviewers concern, the chemicals which were used were analytical standard and purchased from Sigma Aldrich.
5. Plant preparation: roots were pulverized….. or they were extracted without any previous processing.
Answer:-
As for the reviewers concern, the plant preparation was explained in detail.
6. Soxhlet extraction: The yield from different extract (chloroform, ethyl acetate,….) were……. The extract was dried over anhydrous…..
Answer:-
As for the reviewers concern, the above sentence was corrected in the manuscript.
7. GC-MS analysis …The HP5 column is not optimal for fatty acid analysis…. Do you? The authors should explain in more detail about the components identification
Answer:-
As per the reviewers suggestion the detail methodology of GC-MS analysis was included in the methodology.
8. The larvicidal bioassay methodology is crucial in the manuscript: It would be interesting to include more information.
Answer:-
As per the reviewer suggestion, the details of larvicidal bioassay was included in the methodology.
9. Larvicidal activity ….. Page 4, line 1 : “The GC-MS results……”
Answer:-
As for the reviewer concern, the above sentence was wrongly written and it was corrected in the manuscript.
10. Inappropriate data analysis and also inconsistent with the results presented.
Answer:-
As per the reviewer suggestion, the data analysis was explained properly in the methodology.
11. The table 1 is not presented clearly; especially because it has a difficult reading and there are significant structure mistakes (9,10-octadecadienoic …. Z or E? )
Answer:-
As per the reviewers suggestion the table. 1 was formatted and included in the manuscript.
12. It really seems to not much care was taken to reliably identify compounds and rather just run a library search, which is bad practice.
Answer:-
As for the reviewer concern, the GC-MS screening was performed and characterized using NIST library and the obtained results were revealed in our manuscript. We focused mainly on detecting the insecticidal activity of plant extracts against the arthropod vectors. We take the reviewers valuable suggestion and we will try to improve and explore broadly on the characterization of crude extracts of D. Hamiltonii and their major derivatives in our future research.
13. I don't really understand the results of the statistical analysis that has been done.
Answer:-
As for the reviewer concern, the larvicidal experimental data were exposed to the analysis of variance (ANOVA, and square root transformed percentages) and the obtained statistical results were considered as a five replicates means. Statistical significance within each larvicidal groups were analyzed using Tukey’s multiple range test (significance at p<0.05) and the lethal concentrations of larvae in 24 h were calculated by the Probit analysis with a dependability interval of 95% using the Minitab®17 program. Also, as for the better understanding the larvicidal activity presented on the table was displayed as graph plot as per the reviewer suggestion.
14. Inaccurate conclusions on assumptions that are not supported by your data
Answer:-
As per the reviewer suggestion, the conclusion part was revised.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments to the Authors The paper entitled " Biological activity and non-target potential of root extract Decalepis hamiltonii (Wight & Arn) and their chief derivatives Octadeconic acid and Oleic acid against three mosquito vectors and mosquito predators. Overall, the present research highlights the chemical characterization of crude methanol extracts of D. hamiltonii, their insecticidal activity against the medically challenging pests, and their non-target activity delivers an ecologically safe, and target specific bio-active agents and suitable substitute for chemical pesticides. The overall, manuscript is well designed and presentation of data seems to be good.
1. Abstract section Line No. 45 indicates ‘aquatic predators revelas that the crude’ should be ‘aquatic predators reveals that the crude’. 2. Introduction needs add some information about plant based bioactive molecules control the biological activity with recent updates. 3. In materials and method section GC-MS analysis will be improved, and detailed information given. Mosquito culture section; Include the three major mosquito vector names. 4. Line No. 161 the IV instar larvae should be ‘Fourth instar larvae’ 5. Discussion section needs to be added current references with relevant information about the study. 6. Conclusion section needs to develop according to the results. 7. Once author should check the English and grammatical error in the entire manuscript
Author Response
Reviewer-II:
The paper entitled " Biological activity and non-target potential of root extract Decalepis hamiltonii (Wight & Arn) and their chief derivatives Octadeconic acid and Oleic acid against three mosquito vectors and mosquito predators. Overall, the present research highlights the chemical characterization of crude methanol extracts of D. hamiltonii, their insecticidal activity against the medically challenging pests, and their non-target activity delivers an ecologically safe, and target specific bio-active agents and suitable substitute for chemical pesticides. The overall, manuscript is well designed and presentation of data seems to be good.
Answer:-
We thank the reviewer for his valuable suggestion and feedback on our manuscript. As per the reviewer suggestion all the comments were rectified in our manuscript.
- Abstract section Line No. 45 indicates ‘aquatic predators revelas that the crude’ should be ‘aquatic predators reveals that the crude’.
Answer:-
As per the reviewer suggestion it was changed.
- Introduction needs add some information about plant based bioactive molecules control the biological activity with recent updates.
Answer:-
As per the reviewer suggestion the introduction was update with the information on plant derived extract against the insect pests.
- In materials and method section GC-MS analysis will be improved, and detailed information given. Mosquito culture section; include the three major mosquito vector names.
Answer:-
As per the reviewer suggestion, the GC-MS and mosquito culture section was updated.
- Line No. 161 the IV instar larvae should be ‘Fourth instar larvae’
Answer:-
As per the reviewer suggestion it was modified.
- Discussion section needs to be added current references with relevant information about the study.
Answer:-
As per the reviewer suggestion the discussion part was improved by adding recent references.
6. Conclusion section needs to develop according to the results.
Answer:-
As per the reviewer suggestion, the conclusion part was improved.
- Once author should check the English and grammatical error in the entire manuscript.
Answer:-
As per the reviewer suggestion, the grammar was improved throughout the manuscript.
Author Response File: 
Author Response.doc
Round 2
Reviewer 1 Report
- It would be convenient to change 9,12-octadecadienoic acid methyl ester (the chemical name is incomplete) to linoleic acid methyl ester, throughout the manuscript.
- Please, delete the structure of 9Z,12Z-octadecadienoic acid methyl ester in table 1 and formulate the correct one. It is included in the attached file or you can use the free ACD/labs program.
- Indicate in the manuscript that only the volatile fraction of the methanolic extract has been studied, so a further and deep study is absolutely necessary to determine, the total composition of the methanol extract.
Comments for author File: Comments.pdf
Author Response
Response to Reviewers Comments and Suggestions: - We thank the reviewers and the section editor for their revision and thoughtful comments on our manuscript. We have carefully taken reviewers comments into consideration in preparing our revision for publication, which has resulted in a paper that is clearer, more compelling, and broader. The following summarizes how we responded to reviewers. Reviewer-I It would be convenient to change 9,12-octadecadienoic acid methyl ester (the chemical name is incomplete) to linoleic acid methyl ester, throughout the manuscript. Answer: - As per the reviewer suggestions we have modified the above-mentioned chemical name throughout the manuscript. Please, delete the structure of 9Z,12Z-octadecadienoic acid methyl ester in table 1 and formulate the correct one. It is included in the attached file or you can use the free ACD/labs program. Answer: - Yes, we deleted and included the chemical structure in Table 1 suggested by the reviewer attached file. Indicate in the manuscript that only the volatile fraction of the methanolic extract has been studied, so a further and deep study is absolutely necessary to determine, the total composition of the methanol extract. Answer: - We agree the reviewer suggestions of our work, in our future study will working on this area and will publish next paper as per suggested in depth of study.
Author Response File: Author Response.pdf
