Effects of Various Drying Methods on Selected Physical and Antioxidant Properties of Extracts from Moringa oliefera Leaf Waste

Round 1

Reviewer 1 Report

The authors presented the effects of drying methods on the physicochemical, total phenolic, total flavonoid contents, and antioxidant activity of extracts from the waste of Moringa oliefera L. leaves. Before the publication, several points need to be clarified.

1. Please review the processing technologies of Moringa oliefera L. leaves in the introduction.
2. Through the entire manuscript, the units need to be revised.
3. For the color results, the color parameters need to be explained in detail.
4. The illustrations of Aa, Ba, etc. need to be mentioned in the manuscript.
5. The explanations in sections 3.3 and 3.4 seem not match with the results in Tables.
6. The quality of figures need to be uplifted, especially in Fig.3 and 4.
7. In discussions, the relations among total phenolic, total flavonoid contents, and antioxidant activity of extracts resulting from the drying methods and various extracting solvents do not fit the presented results. Please make clear description. 
8. The authors mention that the research results could reduce environmental risk in MO processing industry. Is there any quantitative results?

Author Response

Dear Respective Reviewer,

We are deeply grateful for all your valuable comments on our manuscript. We agreed and revised our manuscript following your comments and suggestions. We send two files: of which a file is noted with track changes and color letters to indicate where we revised, and a file is the final revised manuscript. The responses to each of your questions are detailed in the table below. Please kindly check.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors aim to investigate the efficiency of different solvent extraction methods on Moringa leaves which were dried in a sun-drier or a tray-drier. They use standard photometric and inhibition assays to quantify the content of chemical compound classes and the anitoxidant activity in these extracts.

The chemical-analytical methodology of the study is sound. The English language requires extensive editing, but I could understand the manuscrit well enough.  I think that the manuscript would need extensive re-writing and additional experimental data before it should be published. I have concerns about the design and presentation of the study that I will outline in the following in the hope that the authors wil incorporate some of my suggestions in the next version of the manuscript.

My main criticism concerns the design of the study. The authors collected one batch sample of leaves, split it in two parts, and dried those two sub-samples once on different driers. Then, these sub-samples were extracted three times with each of three different solvents. This means, that the replication for each solvent within each drying method is three but the replication of the drying method itself is one. Therefore, a statistical comparison of the two drying methods is not possible.

Thus, the data can only be interpreted within each drying method and thus the study focuses on a comparison of extraction efficiency of three well established solvents with different polarity for well documented compound classes. This severely reduces the novelty of the study.

In addition I have concerns with the phrasing of the introduction paragraph

Line 49: “The capability of these plants in medicinal utilization is mainly attributed to their antioxidant properties” I think this is too narrow. Medicinal plants can have a lot more functions. Even phenolics themselves can have antibiotic properties on bacterial cultures for example.

The use of Moringa as food supplement is well supported by its chemical composition. And the nutritive properties of Moringa are well documented. There is also quite some literature about positive effects of antioxidants in general, and flavonoids in particular in human diet.

In the current manuscript, the authors focus in their introduction quite strongly on potential medicinal applications of Moringa (which might suggest to non-professional readers that the authors talk about effects on humans), although the literature they cite is almost exclusively based on cell-line studies and mice model systems. The use of Moringa in “traditional herbal medication” of humans does not mean that it actually worked, especially when applied to serious diseases with well-known causes like diabetes and cancer. The effects of specific compound classes on-cell lines or in diets of mice are also of limited value for the evaluation of the medicinal value for humans. The formulations the authors use, are in my opinion much too confident given the evidence they cite for these effects, and the formulations are so broad that I see a risk that readers will over-interpret the information given in the introduction.

For example in line: 73 ff. “These off-grade leaves might be possessed phenolic and flavonoid contents [19]. These compounds have numerous biological activities, including antioxidants, anticarcinogenic, immunomodulatory, antidiabetic, antiatherogenic, hepatoprotective functions and the regulation of thyroid status [20].” In the cited study [20], the authors (Cajuday et al. 2010) fed hexane-extract of Moringa leaves to male mice and dissected their reproductive organs. It has nothing to do with any of the statements about phenolics or flavonoids.

As the flavonoids and antioxidant compound classes are the focus of the study, I would strongly encourage the authors to re-write the introduction and to stay on focus on the chemical and nutritional topic of these compounds and Moringa, which is well supported by scientific evidence. Especially as the authors do not relate any of the discussion to the medicinal points (which I agree with). In my opinion there is no need to overstate the value of Moringa as an anti-cancer plant, it is valuable enough as it is. The Paragraph about drying methods in the discussion should be moved to the introduction paragraph and I would include the basics about chemistry (polarity of solvents etc. into the introduction rather than the discussion paragraph).

comments to the methods section

Line 87: Since drying and storage of the leaves were focus of the study, information about how old the leaf waste was and how it was stored before the authors collected it would be of interest.

Line 94: After the waste was collected, it was split into two samples and dried in two different ways. How was the sample split? Were two batches of waste collected independently and the washed and dried or was one big bag collected, mixed, washed and then split into two batches? This information is vital, as it determines whether the two samples were comparable

Please explain, how a sun drier and a tray dryer works.

Line 113: please state the equation.

Line 114: “samples were analysed in triplicate” and then the means reported, or the median?

Line: 138: please state which statistical program was used and which factors were included. Full factorial ANOVA with one replicate for the drying method can be calculated but the results are not interpretable.

Figure 1: Legend symbols are not readable

Figure 4b: the linear model does not fit the data.

Figure 4 legend: please explain in the figure legend all abbreviations, number of replicates, and method used to calculate the correlation (Pearson’s?).

 

 

 

 

Author Response

Dear Respective Reviewer,

We are deeply grateful for all your valuable comments on our manuscript. We agreed and revised our manuscript following your comments and suggestions. We send two files: of which a file is noted with track changes and color letters to indicate where we revised, and a file is the final revised manuscript. The responses to each of your questions are detailed in the table below. Please kindly check.

Author Response File: Author Response.pdf

Reviewer 3 Report

The article presented for review, entitled "Effect of various drying methods on the physicochemical and anti-radical properties of extracts from the waste of Moringa oliefera leaves", presents the results of the analysis of antioxidant properties and selected physical properties of Moringa oliefera leaf waste.
After reading the manuscript, I suggest corrections
All suggestions are included in the text
I suggest changing the title - adequately to the content
I suggest supplementing the methodology of describing the statistical analysis
I suggest completing the discussion - referring to the analyzes performed and the results obtained, e.g. for what purpose the pH or acidity was analyzed, the color was not discussed, apart from stating that it is different for the drying methods used - which method the authors suggest, and maybe the color does not matter in the analyzes?
I suggest suggesting a solvent for the preparation of extracts in the conclusions?

Comments for author File: Comments.pdf

Author Response

Dear Respective Reviewer,

We are deeply grateful for all your valuable comments on our manuscript. We agreed and revised our manuscript following your comments and suggestions. We send two files: of which a file is noted with track changes and color letters to indicate where we revised, and a file is the final revised manuscript. The responses to each of your questions are detailed in the table below. Please kindly check.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have modified the manuscript accordingly. However, the qualities of figures and captions need to be improved. 

Author Response

Dear Respective Reviewer,

We are deeply grateful for all your valuable comments to our manuscript. We agreed and revised our manuscript following your comments and suggestions. We send two file: of which a file is noted with track changes and color letters to indicate where we revised, and a file is the final revised manuscript. The responses to each your questions are detailed in the table below. Please kindly check.

Author Response File: Author Response.pdf

Reviewer 2 Report

I thank the authors for revising the manuscript.

The added information about the proper replication of the drying methods adds substantial value to the manuscript. I am also greatful that the authors revised the introduction paragraph and removed most of the medicinal and traditional medicinde claims. Most of my initial concerns were addressed.

The manuscript does not contain major methodological flaws at this stage, however I suggest the athours invest some time to improve the language and the presentation of the figures and tables. I think,  the manuscript  would greatly benefit from editing by a professional or a native speaker to improve readability and to avoid misunderstandings. Overall, the figures and tables  are not finally formatted. Text is overlapping here and there, axes and text are not aligned properly etc.

I still have a few minor comments I suggest the authors respond to.

Line148: I thank the autors for stating the equation as requested. From the last version of the manuscript, I assumed there was a fixed formula by which to calculate the phenolic content using the absobtion values at one or more wavelengths. Now it seems, the authors used a standard curve to calculate the unknown values. Then I would suggest to rather  state this in the text, as the equation by itself is not informative.

Table 4: please align the text and  adjust the formatting

Figure 4:  I thank the athors for their reply to my initial comment “the linear model does not fit the data” on Fig. 4b. However I honestly do not understand what they mean by it.  First, their reply seems to focus on Fig. 4a, which I never talked about. Second, the R² value of the linear model is only meaningful, if the values of fit of two modesl on the same dataset are compared. Not between different datasets. At least to me, the line in Fig. 4b clearly does not fit to the curved pattern the data suggest. I would recommend using an exponential equation or to transform the data in order to fit the linar model. Also, this figure is not yet properly formatted. The text-field “b” in Fig. 4b covers part of the datapoint, Fig. 4c is not aligned properly, font sizes differ, text is coverd by the axis in Fig.4b.  

Author Response

Dear Respective Reviewer,

 

We are deeply grateful for all your valuable comments on our manuscript. We agreed and revised our manuscript following your comments and suggestions. We send two files: of which a file is noted with track changes and color letters to indicate where we revised, and a file is the final revised manuscript. The responses to each of your questions are detailed in the table below. Please kindly check.

Author Response File: Author Response.pdf