Synthetic Melatonin and/or Phytomelatonin Contents in Different Commercial Phytotherapeutic Supplements
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsI congratulate the authors on the interest of the subject of their article. The presence of phytomelatonin in some plants and the real effect it can have on the human organism is a very interesting subject, with a future of possible use, as well as exciting. However, I missed more specificity on the separate content of melatonin and phytomelatonin, as well as investigation of the specific phytomelatonin content from the plant species of the studied products. I would also have been interested to see a discussion of the joint effect of melatonin and phytomelatonin with the other sleep-acting plant active ingredients/principles.
Author Response
Rev.#1
I congratulate the authors on the interest of the subject of their article. The presence of phytomelatonin in some plants and the real effect it can have on the human organism is a very interesting subject, with a future of possible use, as well as exciting. However, I missed more specificity on the separate content of melatonin and phytomelatonin, as well as investigation of the specific phytomelatonin content from the plant species of the studied products. I would also have been interested to see a discussion of the joint effect of melatonin and phytomelatonin with the other sleep-acting plant active ingredients/principles.
Response: Thank you for your positive feedback. With regard to your request for more information on phytomelatonin in the plant species of products, I would like to inform you that, as far as we know, the data on this are scarce. I recommend reading our recent review on it (ref. 32) where some data were presented. Also, only our paper on valerian roots (ref.40) studied this type of relationship of phytomelatonin with other sleep-activating agents (valerenic acid).
Reviewer 2 Report
Comments and Suggestions for AuthorsThe present work is very interesting and intended to investigate the quantitative differences that exist between the melatonin contents indicated in the products and in the products themselves that were subsequently analysed. In conclusion, in the tested product, the total melatonin value is below the manufacturer's specifications, between 5-68% and the use of natural preparations rich in phytomelatonin that do not contain by-products of the synthetic molecule is recommended.
Results obtained are well explained and data interpretation is also correct. Conclusions are consistent with the evidence and arguments presented. The strengths of this study are precisely in its innovative nature and in the comparison over time of the same formulations which have often revealed a total loss of melatonin.
The authors themselves offer many suggestions preferring the use of only herbal food supplements with a sufficient phytomelatonin content to eliminate the inclusion of chemically synthesized melatonin in the preparations.
Moreover, about references 1-7, 16, 17, 30 and 33-35 the date of their publication is too old and authors should modify them.
Author Response
Rev.#2
The present work is very interesting and intended to investigate the quantitative differences that exist between the melatonin contents indicated in the products and in the products themselves that were subsequently analysed. In conclusion, in the tested product, the total melatonin value is below the manufacturer's specifications, between 5-68% and the use of natural preparations rich in phytomelatonin that do not contain by-products of the synthetic molecule is recommended.
Results obtained are well explained and data interpretation is also correct. Conclusions are consistent with the evidence and arguments presented. The strengths of this study are precisely in its innovative nature and in the comparison over time of the same formulations which have often revealed a total loss of melatonin.
The authors themselves offer many suggestions preferring the use of only herbal food supplements with a sufficient phytomelatonin content to eliminate the inclusion of chemically synthesized melatonin in the preparations.
Response: Thank you for your positive feedback.
Moreover, about references 1-7, 16, 17, 30 and 33-35 the date of their publication is too old and authors should modify them.
Response: All these references are necessary as they were pioneering references that caused great impact and are commonly used as historical references that marked a milestone.
Reviewer 3 Report
Comments and Suggestions for AuthorsDear authors,
I have analyzed the work and I would like to make a few remarks:
- the content is rendered in a school-like manner and does not rise to the level of academic rigor.
- the introduction is oversized, the figures need to be cited,
- in table 1, what is the melatonin content expressed in??
- please indicate bibliographic references to all the analysis methods used
-for the chromatographic method, please attach the calibration curves and examples of chromatograms for standards and samples
-what is the purpose of the data in table 1
- which is relevant and the novelty of the research;
- in table 2, not all values ​​have the same unit of measure. are you sure that what you measured is correct? can you fight with the producers because they do not correctly detect the quantities of the marketed product? have you checked your results in other laboratories with standardized devices?
-what is the role of the study from point 3.2, the supplements are valid for 4 years? Please provide arguments for what you say in relation to other publications.
Author Response
Rev.#3
Dear authors,
I have analyzed the work and I would like to make a few remarks:
- the content is rendered in a school-like manner and does not rise to the level of academic rigor.
Response: We think that the MS is written to cover a wide audience since the subject is of scientific interest but also social given the high number of consumers of this type of supplements.
- the introduction is oversized, the figures need to be cited,
Response: Thank you for your suggestion. We have shortened a few paragraphs and quoted the figures.
- in table 1, what is the melatonin content expressed in??
Response: We have corrected the error. Table 1 presents the melatonin content (in mg/tablet) of each of the products indicated by the manufacturer.
- please indicate bibliographic references to all the analysis methods used
Response: References have been included.
-for the chromatographic method, please attach the calibration curves and examples of chromatograms for standards and samples
Response: We have tried not to obtain a too extensive MS, and since the information provided by the chromatograms and calibration curves can be observed in our previous papers (refs. 40, 41 and 42), we chose not to include them, although we remain at the disposal of the editor to include them as supplementary material.
-what is the purpose of the data in table 1
Response: Table 1 presents the melatonin content (in mg/tablet) of each of the products indicated by the manufacturer and also the herb composition content.
- which is relevant and the novelty of the research;
Response: The main objective was to verify to what extent the contribution of phytomelatonin (from MAPs) was relevant in the total melatonin content of several phytopreparations. Thus, various commercial preparations containing only synthetic melatonin, containing synthetic melatonin and medicinal-aromatic plants (MAPs) and containing only MAPs were analyzed.
- in table 2, not all values ​​have the same unit of measure. are you sure that what you measured is correct?
R: In table 2 all quantifications are given in mg melatonin/tablet, except for those of sample #13 which corresponds to μg melatonin.
can you fight with the producers because they do not correctly detect the quantities of the marketed product? have you checked your results in other laboratories with standardized devices?
Response: Thank you for your suggestion. We have extensive experience in melatonin and phytomelatonin determinations, applying widely used methods and verifying our results with various techniques such as LC-fluorescence, LC-MS/MS and ELISA. In any case, these are the analyses of commercially acquired samples, which are available to manufacturers to carry out a more detailed study of their products containing melatonin.
-what is the role of the study from point 3.2, the supplements are valid for 4 years? Please provide arguments for what you say in relation to other publications.
Response: Due to our surprise when verifying the large differences in the melatonin content of manufactured products as indicated on the labels, we were forced to verify whether these large downward quantitative differences were due to the passage of time between their manufacture and consumption. We have not been able to find references in this regard.
Reviewer 4 Report
Comments and Suggestions for AuthorsThe article presents an interesting study of several commercial supplements commonly used by the population. Authors analyze the actual composition of each of these supplements and compare it with the specifications described on the labels. They found that most of the products analyzed (11 of 12) contained less melatonin than indicated on the label. Authors also analyse the shelf life of some products after three years, finding that the expiry date should be revised on some of them.
I consider this article could be accepted after minor revisions and clarifications that I detail below:
Figure 2 includes text (in blue tables) with a font size that is too small to read.
Table 3: why were products 9 to 13 not analyzed three years later like the others?
Conclusions: line 2018; what is the supplement with 104% extra melatonin content?
References: why some references include the doi but others do not? There are a slightly high number of self-citations (8 out of 49, 16%) and some of them are more than 15 years old, but I consider them all justified and appropriate.
Lines 272 and 338: years 2021 and 2024 should be written in bold.
Lines 275 and 288 include a strange symbol in the names of some authors.
Author Response
Rev.#4
The article presents an interesting study of several commercial supplements commonly used by the population. Authors analyze the actual composition of each of these supplements and compare it with the specifications described on the labels. They found that most of the products analyzed (11 of 12) contained less melatonin than indicated on the label. Authors also analyse the shelf life of some products after three years, finding that the expiry date should be revised on some of them.
I consider this article could be accepted after minor revisions and clarifications that I detail below:
Figure 2 includes text (in blue tables) with a font size that is too small to read.
Response: The Figure has been modified to improve this aspect.
Table 3: why were products 9 to 13 not analyzed three years later like the others?
Response: This was because samples 1 to 8 were representative of the rest; that is, its herbal composition is very similar to #9, #11 and #12; #10 did not contain herbs and #13 had negligible melatonin values (μg).
Conclusions: line 2018; what is the supplement with 104% extra melatonin content?
Response: There is a mistake in that sentence. Only product #5 presents an increase in melatonin explainable by the contribution of MAPs (31.1%). The 104% data (in Conclusion section) refers to sample #13, where 100% of its melatonin content is attributable to MAPs since it does not contain added chemical melatonin. We have re-written this phrase in the Conclusions section.
References: why some references include the doi but others do not? There are a slightly high number of self-citations (8 out of 49, 16%) and some of them are more than 15 years old, but I consider them all justified and appropriate.
Response: The appearance or not of the DOI in the references is an editorial decision. Many old references are necessary as they were pioneering references that caused great impact and are commonly used as historical references that marked a milestone.
Lines 272 and 338: years 2021 and 2024 should be written in bold.
Lines 275 and 288 include a strange symbol in the names of some authors.
Response: These mistakes have been corrected.
