Design, Synthesis and Antifungal Activity of Novel Benzoylcarbamates Bearing a Pyridine Moiety
Round 1
Reviewer 1 Report
In this manuscript, the authors represent a synthesis of pyridine-containing benzoyl carbamates and evaluation of their anti-fungal activities. Overall, the study was well done and suited for the publication in Applied Sciences. Please check the following minor revised points.
1) In line 200, compound 4g is incorrect. (4h)
2) Line 216-217 should be repositioned to line 213. (Above the table 1)
3) Question: Why does the authors choose 3-substituted pyridine, not 2-substituted one.
Author Response
Response to Reviewer 1 Comments
Point 1: In line 200, compound 4g is incorrect. (4h)
Response 1: The error is corrected, and the sentence “Among them, compound 4g had the best activity (EC50, 10.85μg/mL)” is deleted, and it was expressed in another statement at the end of this paragraph.
Point 2: Line 216-217 should be repositioned to line 213. (Above the table 1)
Response 2: Line 216-217 is repositioned.
Point 3: Q uestion: Why does the authors choose 3-substituted pyridine, not 2-substituted one.
Response 3: We referenced the structure of an excellent fungicide pyrifenox, 2,4-dichloro-2-(3-pyridyl)acetophenone-O-methyloxime, in which the pyridine is 3-substituted one.
Author Response File: 
Author Response.docx
Reviewer 2 Report
In the present article the authors have reported detailed synthesis of ten novel pyridinyl benzoylcarbamate that showed moderate to cytotoxicity against Sclerotinia sclerotiorum and Botrytis cinerea, two very common fungi that affects quality and production of fruits and vegetables. The manuscript is well written with detailed synthetic methods and analysis data along with discussions of the NMR analysis. The cytotoxicity data supports the claim that has been made in the manuscript and there is one compound that has potential to be a lead compound, according to the authors claim, subjected to further studies suggest so. In this context, I consider the present work is important and should be considered for publication after the following revision:
1. Chlorothalonil is widely used in many commercial products for its activity against Sclerotinia sclerotiorum and Botrytis cinerea, and none of the reported compounds in the manuscript showed any better cytotoxicity than Chlorothalonil. Please provide a discussion with relevant reference or other normal cell toxicology data to explain why the “compound 4h” can be considered as a lead while there is already a better potent compound is in the market.
2. Please provide activity comparison of “compound 4h” with diethofencarb, tolprocarb and benthiavalicarb-isopropyl that are popular carbamate fungicides with discussion.
Author Response
Response to Reviewer 2 Comments
Point 1: Chlorothalonil is widely used in many commercial products for its activity against Sclerotinia sclerotiorum and Botrytis cinerea, and none of the reported compounds in the manuscript showed any better cytotoxicity than Chlorothalonil. Please provide a discussion with relevant reference or other normal cell toxicology data to explain why the “compound 4h” can be considered as a lead while there is already a better potent compound is in the market.
Response 1: In “3.2. Antifungal Activity”, we illustrated the antifungal activity of compound 4h at the end of the first paragraph, and explained possible reason that 4h exhibits good activity at the end of the second paragraph, which was seen in our revision in detail.
Point 2: Please provide activity comparison of “compound 4h” with diethofencarb, tolprocarb and benthiavalicarb-isopropyl that are popular carbamate fungicides with discussion.
Response 2: We chose diethofencarb as new positive control, and supplemented its antifungal activity, in order to better evaluate the activity of reported compounds.
However, we can not obtain fungicides tolprocarb and benthiavalicarb-isopropyl, so we did not perform their antifungal activity. It is very pity.
Author Response File: Author Response.docx
Reviewer 3 Report
The paper of Jiang and co-workers deal with the design, synthesis, and antifungal activity of benzoylcarbamates incorporating a pyridine ring. The introduction and conclusion are poor and should be improved. The design is convincing and all synthesized molecules have been correctly characterized; moreover, their purity has been assessed by elemental analysis.
Since the authors claimed that tolprocarb and picarbutrazox were chosen as lead compounds to design the new molecules they should use these molecules as references for test the antifungal activities; only if the activities of the new synthetized molecules are comparable or better than that of the reference compounds the paper can be accepted.
Moreover, the benzoylcarbamates are used as prodrugs; so, the authors should test the stability of new compounds to assure that their activity is due to the entire molecule.
Finally, recently has been proposed that the target site of tolprocarb is the polyketide synthase (J. Pestic. Sci. 2014, 39, 152–158); so, should be interesting to perform a docking study that could demonstrate the modality of action of the new compounds and, contemporarily, assess a better SAR conclusion.
I suggest to reorganize the paper and resubmit it for reconsideration.
Author Response
Response to Reviewer 3 Comments
Point 1: Since the authors claimed that tolprocarb and picarbutrazox were chosen as lead compounds to design the new molecules they should use these molecules as references for test the antifungal activities; only if the activities of the new synthetized molecules are comparable or better than that of the reference compounds the paper can be accepted.
Response 1: Indeed, we should test antifungal activity of tolprocarb and picarbutrazox, in order to well evaluate the activity of target compounds. Because tolprocarb and picarbutrazox are both new fungicides, however, we can not get them. Therefore, we chose another carbamate fungicide, diethofencarb, as new positive control, and supplemented its antifungal activity, in which its activity was better than that of the synthesized compounds. On other hand, in the discovery of pesticide, the activity of designed compound is not higher than that of the lead compound in many cases.
Point 2: Moreover, the benzoylcarbamates are used as prodrugs; so, the authors should test the stability of new compounds to assure that their activity is due to the entire molecule.
Response 2: In the fungicidal activities test, we use the mycelium growth rate method, and this method only gives in vitro preliminary activity result. Because the antifungal activities of synthesized compounds were not high enough, we didn’t further evaluate their property. Additionally, it is said that benzoyl carbamates are relatively stable in near natural solution (Wu, Z.P.; Gao, W.; Yang, H. Progress on the Analysis of Carbamate Pesticide Residues, Chinese Jiangsu Chemical Industry, 2004, 32(5): 24-27), and their half-lives are 0.02-0.1 year, that is 7.2-36.5 day. Therefore, in our test period (about 3 days), the synthesized compounds might be stable.
Point 3: Finally, recently has been proposed that the target site of tolprocarb is the polyketide synthase (J. Pestic. Sci. 2014, 39, 152–158); so, should be interesting to perform a docking study that could demonstrate the modality of action of the new compounds and, contemporarily, assess a better SAR conclusion.
Response 3: We thank the reviewer’s suggestion and have read the reference carefully. In our college, there is no condition to perform docking study, it’s very pity.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
The authors have addressed all the comments made by the reviewer during the first phase of review and provided reasonable information and discussion that was asked for within the scope of the manuscript. Though, according to the EC50 values, the new compound 4h appears less potent compared to the currently used compounds that are presently in the market, the potency of 4h is good enough to serve as a lead compound for further development. At the present age of antimicrobial resistance, any new lead compound is always welcome for further studies. In this context, the finding in the manuscript is important. Hence, I recommend the present article to be published in its present form.
Author Response
There is no question to response
Reviewer 3 Report
The authors eluded some critical comments mine and of Reviewer 2. They not improved both introduction and conclusion, as suggested. Moreover, they not provide a discussion with relevant reference or other normal cell toxicology data to explain why the “compound 4h” can be considered as a lead while there is already a better potent compound in the market.
I suggest to articulate in more detail what was requested and, above all, to provide a convincing explanation on the possibility of considering the compound 4h as a new lead.
Author Response
Response to Reviewer 3 Comments
The authors eluded some critical comments mine and of Reviewer 2. They not improved both introduction and conclusion, as suggested. Moreover, they not provide a discussion with relevant reference or other normal cell toxicology data to explain why the “compound 4h” can be considered as a lead while there is already a better potent compound in the market.
I suggest to articulate in more detail what was requested and, above all, to provide a convincing explanation on the possibility of considering the compound 4h as a new lead.
Response: We have improved introduction and conclusion.
In introduction, we added two portions: (1) The study on a kind of aryl carbamic acid-5-aryl-2-furanmethyl esters, including their antifungal activity and possible mechanism; (2) A simple description of target compound molecules, in order to illustrate their structural characteristics.
In conclusion, we emphasize the notable antifungal activity of compound 4h. On the other hand, because we have not enough relevant reference or other normal cell toxicology data to explain why “compound 4h” can be considered as a lead compound, we replaced the last sentence --“compound 4h may be used as a candidate compound for further research” with “Due to its favorable pharmacophore (4-chlorophenyl) in the molecule and sufficient antifungal activity, 4h possessed the value of further structural optimization and bioactivity research”.
Author Response File: Author Response.docx
