Diversity of Plant Colorant Species in a Biodiversity Hotspot in Northern Thailand

Round 1

Reviewer 1 Report (Previous Reviewer 3)

The authors can find below the points that need to be revised:

1. Is this a systemic study or review? Please state it clearly in the abstract. Clearly state that this is a systemic study that aims to investigate.... 

This doesn't seem very clear; please consider it carefully.

2. Material specification: The author provides colors from various plant parts (seeds, flowering parts, leaves, roots, fruits, bark, and whole plants). Including whole plants and comparing them with other parts of plants (interspecies or intraspecies) requires more rationality, considering whole plants contain different metabolites (secondary) as colorants.

2. Extraction Technique specifications: The author mentioned techniques such as chopped boiled, pounded boiled, boiled, soaked in water, soaked in water chopped, etc. These techniques don't seem to be discussed in much detail in the paper. In the manuscript, please provide details about how individual techniques improve the isolation of colorants or specific classes of colorants or structures. As an example for authors, the hydroalcoholic extraction technique isolated preferential high polar-to-moderate polar organic compounds (therefore polyphenolics), while hexane/cyclohexane (or other nonpolar solvents) extract mainly contains hydrophobic constituents such as fatty acids, steroids, etc

3. More technical aspects specificity is required in extraction techniques: as mentioned in point 2, some of these techniques are commonly interchangeable and don't provide substantial differences. For example, the differences in the relative abundance of colorants in solution affect the overall color properties of the extract. Therefore, it is essential to know how one extraction technique plays a critical role in extracting a specific class of colorants; consequently, it makes more rational sense how the color of the extract may vary from one extract to another or sometimes have non-reproducibility. Thus, such information must be provided in the paper. 

4. Color properties: Most colorants with colors were provided as primary colors, as can be seen in Table 4. However, spectrophotometer-based techniques are required to measure the color properties, or at least please mention how these colors were evaluated from extracts. For example, just looking at the extract and deciding the color could be one's subjective perception. Please elaborate on how the color properties were measured and provide sufficient justification for their inclusion in Table 4. Another interesting point is the color properties of an extract depend on the chemical composition or proportion of individual colorants in the extract solution. Therefore, it is mandatory to measure the color properties through analytical techniques.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report (Previous Reviewer 2)

The authors have made a commendable effort in addressing previous comments and contributing novel insights to the ethnobotanical field with their study on plant colourant species in northern Thailand, a recognized biodiversity hotspot. The manuscript has the potential to make a significant contribution to the literature. However, I believe the manuscript could be further improved in several areas to enhance its scientific rigour and clarity. My primary concerns are outlined below:

The current formulation of the research questions lacks the specificity required for a study of this nature. I recommend reformulating them better. This will sharpen your research's focus and facilitate a more structured and impactful Discussion section.

The manuscript appears to contain repetitive information within lines 82-86. I suggest carefully reviewing all text to identify and eliminate any redundancies, possibly by combining or rephrasing sentences to maintain continuity without loss of content.

The manuscript mentions an "extensive collection of flora and ethnobotanical documents relevant to northern Thailand" but does not provide sufficient details about the nature and use of these documents. It is unclear whether these documents are part of a literature review, a specialized database, or a physical collection. Providing a more precise description or context would greatly help readers understand the foundation of your research and its methodological approach.

If the manuscript incorporates a review of 42 specific works, including a comprehensive table summarizing these sources would be beneficial. This table should detail the authors, publication year, key findings, and relevance to the current study. Such an organized presentation can enhance the manuscript's readability and underscore the research gap your study aims to address.

The discussion section of the manuscript predominantly reiterates the results rather than interpreting them in the context of the broader field. This section should aim to elucidate the implications of your findings, relate them to existing research, discuss potential limitations, and propose avenues for future studies. 

The manuscript presents a promising study that could contribute significantly to the ethnobotanical field. I look forward to seeing the revised manuscript and believe that these improvements will make a substantial difference in the presentation and impact of your research.

Moderate editing of English language required

Author Response

I have revised the manuscript according to your suggestions. The edited text will be highlighted in red. Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report (Previous Reviewer 2)

The manuscript "Diversity of plant colorant species in a biodiversity hotspot in northern Thailand" has addressed several previously raised concerns and is now ready for acceptance.

Minor editing of English language required

Author Response

We made a critical editing and corrected some remaining errors  in the English.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

This article is only based on the analysis of previous literature data, I think the scientific significance is not great.

English is used correct and readable.

Reviewer 2 Report

The paper titled "Diversity of natural dye plants in northern Thailand" illuminates the significance of dye plants and their escalating importance in an era increasingly focused on health and eco-safety. While dye plants are frequently discussed in ethnobotanical studies, there is a clear gap in comprehensive research about them in northern Thailand.

The study employs ethnobotanical indices such as use value (UV), information consensus factor (ICF), and Jaccard's index. This approach not only lends structure and quantifiability to the study but also bolsters the reliability of the findings, facilitating comparisons with other regions.

A significant contribution of this paper is the identification of 104 dye plant species spanning 85 genera and 43 families. The in-depth analysis of the key species, the spectrum of colours they produce, and the most predominant plant families offers a holistic understanding of dye plants in the region.

The paper keenly addresses the burgeoning trend and recognition of natural products, underscoring the importance of safeguarding cultural heritage and championing sustainable usage. While this manuscript shows promise, there are some areas that could benefit from refinement:

Here are some pivotal points for consideration in subsequent versions:

1. Clarify the selection of regions for comparative analysis: While the paper mentions comparisons with adjacent regions, it does not explain how they were chosen. A more transparent justification would enhance the paper's rigour.

2. Elaborate on data collection: The methodology involving the aggregation of 42 references remains ambiguous. The authors should shed light on the sources tapped for this analysis. The statement, “Data on dye plants used by ten ethnic groups across 142 villages were collected from 42 references,” poses questions. It remains uncertain whether the authors conducted ethnobotanical fieldwork across these villages or solely relied on historical sources. This section necessitates considerable enhancement. Furthermore, elucidating the challenges encountered, especially during data collection or engagement with ethnic communities, would render the paper more comprehensive.

3. Clarification on pseudo-informants: The data analysis section should clearly define and justify the use of pseudo-informants.

4. Refine the discussion chapter: This chapter leans more towards presenting results rather than addressing the research questions. Refining the research goals would be prudent, articulating the overarching aim and specific objectives.

5. Potential Applications: The manuscript would gain from an added section that delves into the contemporary applications of these dye plants, particularly in sectors like textiles and cosmetics. Recommendations for future research trajectories or potential industrial collaborations would also be invaluable.

To conclude, the manuscript "Diversity of natural dye plants in northern Thailand" exhibits potential for acceptance, contingent upon major revisions.

English proofreading is needed to ensure the clarity and correctness of the language.

Reviewer 3 Report

Plant-derived colorants are commonly used in several applications (but mainly limited to food pigments or colorants). The author may have performed some systemic study but didn't clearly state enough to make it quite clear in the introduction. The study has considered nearly 40 extracts.

1. A vast number of reports provide information about the colorant compounds that impart these colors or have these coloration properties; However, the information related to their extraction/analysis is completely missing from the paper. The extraction method plays a critical role in extracting specific types of colorants; therefore, the color of the extract may vary from one extract to another. Thus, such information must be provided in the paper. 

For example, blue or purple  color can be imparted by anthocyanins or triphenyl derivatives

green color mainly because of pigments (primarily different forms of chlorophyll)

yellow or orange color due to polyphenols (specifically, flavonoids)

When such information is available in the public domain, therefore it needs to be added to the paper. 

2. Color indexing: The authors provide some information in Table 4. Those colors are mainly primary or their derivatives. There are more colors than the reported ones in the table 4. However, the color properties of any plant extract or plant extract mixture depend on the chemical composition. Simply, UV (colorimetric) measurement will help indicate the extract's exact color. Reflectance spectroscopy is another example that can be used to determine the color. Without analyzing the color properties using such techniques, the perception of color becomes subjective and can easily contain human error (as well).

3. If some of these are used (or reported) to use in food, then can we not call them as colorants than dyes? In my opinion, dyes are mainly used for imparting color surface properties. Please be careful when using such terminologies; mixing them can confuse readers.

4. The scientific names of plants (extracts derived from those plants) are missing. Please add them.