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Insights into Antioxidant Compounds: From Extraction to Mechanism of Action

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Biochemistry".

Deadline for manuscript submissions: closed (15 June 2024) | Viewed by 2988

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Special Issue Information

Dear Colleagues,

Antioxidant compounds have emerged as compounds of significant value due to their ability to counteract oxidative stress, a major cause underlying numerous chronic diseases and aging. As researchers and industries increasingly explore the potential health benefits of antioxidants, it has become imperative to comprehensively investigate both methods for their extraction and the intricate molecular mechanisms driving their activity. The extraction of antioxidant compounds from diverse natural sources, such as plants, fruits, and vegetables, is a dynamic field that holds promise for yielding potent bioactive compounds. Innovative extraction approaches have demonstrated the possibility of enhancing the efficiency of extracting antioxidants while preserving their biological activity.

At the molecular level, the mechanisms by which antioxidant compounds exert their protective effects against oxidative stress remain a trending topic of research. These mechanisms encompass a range of interactions, including the scavenging of reactive oxygen species (ROS), modulation of signaling pathways, etc. By investigating such mechanisms, researchers can uncover the precise ways in which antioxidants counteract oxidative damage, thus paving the way for novel therapeutic interventions.

This Special Issue provides an opportunity for researchers to dive into the intricate world of antioxidants, spanning from innovative extraction techniques to unraveling their mechanisms of action at the molecular level. Authors are encouraged to contribute articles with a focus on extraction techniques that also consider the intriguing molecular mechanisms that drive antioxidant activity. We encourage studies that encompass a wide array of antioxidant compounds, from polyphenols and flavonoids to vitamins and enzymes. By shedding light on these aspects, we aim to enrich our understanding of how antioxidants can be harnessed for therapeutic applications, ultimately contributing to enhanced health and well-being.

Dr. Theodoros G. Chatzimitakos
Guest Editor

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Keywords

  • antioxidants
  • oxidative stress
  • extraction methods
  • bioactive compounds
  • molecular mechanisms
  • reactive oxygen species (ROS)
  • signaling pathways
  • therapeutic applications

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Published Papers (2 papers)

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20 pages, 3121 KiB  
Article
Simultaneous High-Performance Recovery and Extended Acid-Catalyzed Hydrolysis of Oleuropein and Flavonoid Glycosides of Olive (Olea europaea) Leaves: Hydrothermal versus Ethanol Organosolv Treatment
by Hela Refai, Feyrouz Derwiche, Spyros Grigorakis and Dimitris P. Makris
Int. J. Mol. Sci. 2024, 25(14), 7820; https://doi.org/10.3390/ijms25147820 - 17 Jul 2024
Cited by 2 | Viewed by 944
Abstract
Olive leaves (OLLs) are an exceptional bioresource of natural polyphenols with proven antioxidant activity, yet the applicability of OLL extracts is constrained by the relatively high polarity of the major polyphenols, which occur as glycosides. To overcome this limitation, OLLs were subjected to [...] Read more.
Olive leaves (OLLs) are an exceptional bioresource of natural polyphenols with proven antioxidant activity, yet the applicability of OLL extracts is constrained by the relatively high polarity of the major polyphenols, which occur as glycosides. To overcome this limitation, OLLs were subjected to both hydrothermal and ethanol organosolv treatments, fostered by acid catalysis to solicit in parallel increased polyphenol recovery and polyphenol modification into simpler, lower-polarity substances. After an initial screening of natural organic acids, oxalic acid (OxAc) was found to be the highest-performing catalyst. The extraction behavior using OxAc-catalyzed hydrothermal and ethanol organosolv treatments was appraised using kinetics, while treatment optimization was accomplished by deploying response-surface methodology. The comparative assessment of the composition extracts produced under optimal conditions of residence time and temperature was performed with liquid chromatography–tandem mass spectrometry and revealed that OLLs treated with 50% ethanol/1.5% HCl suffered extensive oleuropein and flavone glycoside hydrolysis, affording almost 23.4 mg hydroxytyrosol and 2 mg luteolin per g dry weight. On the other hand, hydrothermal treatment with 5% OxAc provided 20.2 and 0.12 mg of hydroxytyrosol and luteolin, respectively. Apigenin was in all cases a minor extract constituent. The study presented herein demonstrated for the first time the usefulness of using a natural, food-grade organic acid to perform such a task, yet further investigation is needed to maximize the desired effect. Full article
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22 pages, 5975 KiB  
Article
Optimization of Four Different Rosemary Extraction Techniques Using Plackett–Burman Design and Comparison of Their Antioxidant Compounds
by Vassilis Athanasiadis, Theodoros Chatzimitakos, Martha Mantiniotou, Dimitrios Kalompatsios, Konstantina Kotsou, Ioannis Makrygiannis, Eleni Bozinou and Stavros I. Lalas
Int. J. Mol. Sci. 2024, 25(14), 7708; https://doi.org/10.3390/ijms25147708 - 14 Jul 2024
Cited by 3 | Viewed by 1659
Abstract
Rosemary has many medicinal and therapeutic properties and therefore it is important to study how to maximize the recovery of its bioactive compounds. In the present study, four different extraction techniques were used, namely stirring extraction (STE), pulsed electric field-assisted extraction (PEF), ultrasound [...] Read more.
Rosemary has many medicinal and therapeutic properties and therefore it is important to study how to maximize the recovery of its bioactive compounds. In the present study, four different extraction techniques were used, namely stirring extraction (STE), pulsed electric field-assisted extraction (PEF), ultrasound probe-assisted extraction (UPAE), and ultrasound bath-assisted extraction (UBAE). First, some primary experiments were carried out in order to optimize each technique individually through the Plackett–Burman design. Then, each technique was applied under optimal conditions and the results were compared with each other. The optimal total polyphenol content (TPC) of STE is ~19 mg gallic acid equivalents per gram of dry weight (dw), while the antioxidant activity of the extract is 162 μmol ascorbic acid equivalents (AAEs) per gram of dw via FRAP and ~110 μmol AAE per gram of dw via DPPH. As for PEF, the optimal TPC is ~12 mg GAE/g dw, and the FRAP and DPPH values are ~102 and ~70 μmol AAE per gram of dw, respectively. When it comes to UPAE, the optimal TPC is ~16 mg GAE/g dw and the antioxidant capacity of the extract is ~128 μmol AAE/g dw through FRAP and ~98 μmol AAE/g dw through DPPH. UBAE optimal extract yielded ~17 mg GAE/g dw TPC, ~146 μmol AAE/g dw for FRAP, and ~143 μmol AAE/g dw for DPPH. The highest flavonoid content (~6.5 mg rutin equivalent/g dw) and DPPH (~143 μmol ascorbic acid equivalent/g dw) is obtained through UBAE. UPAE has been shown to be more efficient in recovering ascorbic acid (~20 mg/g dw). Additionally, the chlorophyll-to-carotenoid ratios of UPAE and UBAE were 2.98 and 2.96, respectively, indicating that the extracts had a generally positive impact on health. Considering the environmental impact of each extraction technique but also which antioxidant factor needs to be maximized, the most suitable extraction technique will be chosen. Full article
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