Enhanced “Greener” and Sustainable Ultrasonic Extraction of Bioactive Components from Waste Wild Apple (Malus sylvestris (L.) Mill.) Fruit Dust: The Impact of Pretreatment with Natural Deep Eutectic Solvents

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The work is interesting, but the manuscript results confusing in some part and, the results require a deep clarification and discussion and a deep revision of the format of the tables. 

• The introduction is quite confusing. Authors talk about the extraction process (lines 89-92), then about the solvent (lines 93-98), then again about the extraction process (lines 98- 127), then about the solvent (lines 128-148). Please revise it carefully
• The botanical name should be in Italian
• I am not sure that teas and other beverages can be considered as liquid pharmaceuticals. Please clarify and revise the concept
• The properties of organic solvents are repeated too many times in the introduction (lines 78-79, 96-97)
• In my opinion the term green (and related ones) should not be in quotation marks
• table 1 is not clear. Check it
• Equation 1 should be depicted as equation function
• table 3 is not clear. The experiment from 1 to 4 are about the crude extract described in section 2.4.1, whereas the ones from 5 to 8 about the pretreated extracts described in section 2.4.2? my suggestion is to join the two sections and avoid or modify the table to make the text clearer.
• The temperature is reported in K degrees and Celsius degree. Please uniform it. If Celsius degree is selected, check the unit font (°C)
• Table 4 is not clear because the solvent is not always reported as the kind of pretreatment.
• Section 3.1: the condition for UAE are UAE/water, UAE/aEtOH, UAE/aPPG, and UAE/a The a refers to aqueous? Please specify in the text. My suggestion is to use the same acronyms along the whole text and tables
• Section 3.1: the UAE performed on pretreated extract is done only with PPG, based on the results presented in section 3.2. So it is difficult for the readers to have a complete vision of the results, The authors should improve the discussion of the results, maybe discussing firstly the UAE onncrude from HPLC and TPC, TFC, and antioxidant activity pint of view and then on the pretreated. On the other hand, they can join the two sections (3.1 and 3.2) and make a common discussion.
• Authors study only the extraction solvent, not other parameters related to UAE although they stated in the introduction the importance of multiple parameters.
• It is difficult to understand the energy demands and environmental impact of the designed UAE methodologies from Table 5. Which are the parameters related to energy? Which are the paraemters related to environmental impact? In my opinion the energy demand depends on the UAE conditions, which are the same for all the extractions. The environmental impact could be calculated by proper tools, e.g., GAPI AGREE etc

Comments on the Quality of English Language

• English style and language must be improved to make the text more fluent and clearer.

Author Response

The authors would like to express gratitude to Reviewer 1 for the positive evaluation of the paper, as well as helpful suggestions that helped improve the paper.

Most of the suggestions are wholeheartedly accepted.

All amendments are blue colored.

Since some comments are similar to those provided by the other two Reviewers, this was stated in the referred response(s).

Moreover, all other minor corrections and further clarifications throughout the manuscript are also provided as blue colored text.

We provide detailed answers to each comment in the attached document.

Author Response File: Author Response.doc

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript presents an interesting and timely study on the extraction of bioactive compounds from wild apple residues using ultrasound-assisted techniques and pretreatments with four different NADES. The experimental approach is sound, the results are clearly presented, and the conclusions are well supported by the data. From my perspective, the study could be further strengthened by incorporating a quantitative analysis of individual phenolic compounds. This would allow for more precise calculation of extraction yields and provide a more specific assessment than colorimetric methods, which are inherently less selective.

Only few minor observations:

Line 210: Please revise “transformed”, probably you meant “transferred”.

Line 232-243: Please specify the ratio of sample to solvent.

Figure 1 and 2: In my opinion, a table would be considerably more informative than the chromatograms of the different samples. Presenting the data in tabular form could enhance clarity and facilitate comparison across samples.

 

Author Response

The authors would like to express gratitude to Reviewer 2 for the positive evaluation of the paper, as well as helpful suggestions that helped improve the paper.

Most of the suggestions are wholeheartedly accepted.

All amendments are purple colored.

Detailed answers can be found in the attachment document below.

Author Response File: Author Response.doc

Reviewer 3 Report

Comments and Suggestions for Authors

I have reviewed the paper "Enhanced ‘greener’ and sustainable ultrasonic extraction of bioactive components from waste wild apple (Malus sylvestris (L.) Mill.) fruit dust: the impact of pretreatment with natural deep eutectic solvents.". The study is relevant as it proposes an innovative and eco-friendly method for valorizing agro-industrial waste, with potential applications in food, nutraceutical, and pharmaceutical fields. I recommend the manuscript for publication after minor revision to improve clarity and presentation:

1. In line 150 of the Introduction section, check the placement of quotation marks around “greener.”

2. Check the subscripts when writing the compounds in sections 2.2.6, 2.3, and throughout the rest of the manuscript.

3. In the Introduction, further justify the use of the honey-mimicking NADES: why was it chosen for evaluation? Are there previous studies using it?

4. In section 2.4.1, when describing the method, how many grams of crude herbal powder were used? Was it 15 mL/g (as shown in Table 3)?

5. In Tables 3 and 4, clarify more clearly the distinction between samples pretreated with NADES and those without. In particular, the case of 38% PG is confusing regarding whether the sample was pretreated.

6. It would be useful to add a supplementary table (or a table in the manuscript) indicating the retention times of the compounds detected and quantified with UHPLC, so that they can be identified in the chromatograms and the efficiency of the solvents and treatments can be better evaluated.

7. The glucose detected when using the HONEY NADES—could it come from the glucose used to prepare the NADES itself?

8. In the results of Table 4, why does the combination that provides the highest TPC and TFC values show lower DPPH and ABTS values? Are the extracted compounds less antioxidant?

9. In section 3.4, it would also be interesting to include economic considerations: compare the solvents/treatments used in terms of the cost of the raw materials.

10. Finally, in the Conclusions section, if possible, add more specific data from the results, highlight the best combination to use, and also mention potential future steps.

Author Response

The authors would like to express gratitude to Reviewer 3 for the positive evaluation of the paper, as well as helpful suggestions that helped improve the paper. Most of the suggestions are wholeheartedly accepted. All amendments are green colored. Detailed answers to questions and suggestions can be found in the attached document below.

Author Response File: Author Response.doc

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Authors did an ecellent job improving the quality of the manuscript. The revised manuscript can be accepted.