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Spyros Grigorakis
Food Quality & Chemistry of Natural Products, Mediterranean Agronomic Institute of Chania (M.A.I.Ch.), International Centre for Advanced Mediterranean Agronomic Studies (CIHEAM), P.O. Box 85, 73100 Chania, Greece

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Journal article
Published: 14 March 2021 in Applied Sciences
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Quercetin (Qt) is a natural flavonoid of high biological significance, and it occurs in a wide variety of plant foods. Although its oxidation by various means has been extensively studied, its behavior with regard to thermal treatments remains a challenge. The study described herein aimed at investigating Qt thermal decomposition, by proposing an empirical sigmoidal model for tracing degradation kinetics. This model was employed to examine the effect of addition of antioxidants on Qt thermal degradation, including ascorbic acid, L-cysteine, and sulfite. Furthermore, degradation pathways were proposed by performing liquid chromatography-tandem mass spectrometry analyses. Upon addition of any antioxidant used, the sigmoidal course of Qt thermal degradation was pronounced, evidencing the validity of the empirical model used in the study of similar cases. The antioxidants retarded Qt degradation in a manner that appeared to depend on Qt/antioxidant molar ratio. No major differentiation in the degradation mechanism was observed in response to the addition of various antioxidants, and in all cases protocatechuic acid and phloroglucinol carboxylic acid were typical degradation products identified. Furthermore, in all cases tested the solutions resulted after thermal treatment possessed inferior antioxidant properties compared to the initial Qt solutions, and this demonstrated the detrimental effects of heating on Qt. The empirical model proposed could be of assistance in interpreting the degradation behavior of other polyphenols, but its validity merits further investigation.

ACS Style

Abdessamie Kellil; Spyros Grigorakis; Sofia Loupassaki; Dimitris Makris. Empirical Kinetic Modelling and Mechanisms of Quercetin Thermal Degradation in Aqueous Model Systems: Effect of pH and Addition of Antioxidants. Applied Sciences 2021, 11, 2579 .

AMA Style

Abdessamie Kellil, Spyros Grigorakis, Sofia Loupassaki, Dimitris Makris. Empirical Kinetic Modelling and Mechanisms of Quercetin Thermal Degradation in Aqueous Model Systems: Effect of pH and Addition of Antioxidants. Applied Sciences. 2021; 11 (6):2579.

Chicago/Turabian Style

Abdessamie Kellil; Spyros Grigorakis; Sofia Loupassaki; Dimitris Makris. 2021. "Empirical Kinetic Modelling and Mechanisms of Quercetin Thermal Degradation in Aqueous Model Systems: Effect of pH and Addition of Antioxidants." Applied Sciences 11, no. 6: 2579.

Journal article
Published: 11 July 2020 in Applied Sciences
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A series of citrate salts were tested as hydrogen bond acceptors to synthesize deep eutectic solvents (DES) based on lactic acid and glycerol, used as hydrogen bond donors. The DES produced were then screened to identify the highest performing system for the effective extraction of polyphenolic phytochemicals from the medicinal plant Salvia fruticosa Mill. (Greek sage). The most efficacious DES was the one composed of lactic acid and sodium citrate dibasic, at a molar ratio of 15:1 (LA-SCDB15). Furthermore, for the first time there has been evidence concerning DES pH and extraction efficiency. Using this solvent, a batch, stirred-tank extraction process was developed, by employing ultrasonication pretreatment and response surface methodology. The optimal settings determined were stirring speed 900 rpm, proportion of DES/water 77% (w/v), and ultrasonication pretreatment time 15 min. By adjusting these optimal settings, the predicted maximum total polyphenol yield was calculated to be 79.93 ± 1.92 mg gallic acid equivalents g−1 dry mass. The examination of temperature effects demonstrated that the batch, stirred-tank extraction stage was very energy-efficient, with a barrier of 7.64 kJ mol−1. Comparison of the extraction of Salvia fruticosa polyphenols with other green processes previously developed, illustrated the high extraction capacity of LA-SCDB15. The major polyphenols identified in the extracts produced under optimized settings were chlorogenic acid, luteolin 7-O-glucuronide and rosmarinic acid.

ACS Style

Spyros Grigorakis; Abedalghani Halahlah; Dimitris P. Makris. Batch Stirred-Tank Green Extraction of Salvia fruticosa Mill. Polyphenols Using Newly Designed Citrate-Based Deep Eutectic Solvents and Ultrasonication Pretreatment. Applied Sciences 2020, 10, 4774 .

AMA Style

Spyros Grigorakis, Abedalghani Halahlah, Dimitris P. Makris. Batch Stirred-Tank Green Extraction of Salvia fruticosa Mill. Polyphenols Using Newly Designed Citrate-Based Deep Eutectic Solvents and Ultrasonication Pretreatment. Applied Sciences. 2020; 10 (14):4774.

Chicago/Turabian Style

Spyros Grigorakis; Abedalghani Halahlah; Dimitris P. Makris. 2020. "Batch Stirred-Tank Green Extraction of Salvia fruticosa Mill. Polyphenols Using Newly Designed Citrate-Based Deep Eutectic Solvents and Ultrasonication Pretreatment." Applied Sciences 10, no. 14: 4774.

Journal article
Published: 13 June 2020 in Sustainability
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Salvia fruticosa Miller, also known as Cretan or Greek sage, is a medicinal plant with significant biological properties, which are largely ascribed to its polyphenolic composition, but there is to-date a scarcity of green and sustainable processes for efficient polyphenol extraction from this plant. The objective of this study was the implementation of an extraction process that would combine a green solvent based on glycerol, a biodiesel industry by-product, and ultrasonication pretreatment. Ultrasonication for 40 min followed by stirred-tank extraction was shown to provide significantly higher total polyphenol yield than mere stirred-tank extraction, while kinetics indicated 50 °C as the most favorable temperature, with the yield being 92 mg gallic acid equivalents (GAE) per g dry mass. Comparison of this method with a previously developed one that used methyl β-cyclodextrin revealed that the extracts obtained had similar antioxidant activity, and yield in major polyphenols including luteolin 7-O-glucuronide and rosmarinic acid was virtually equal. The current process is proposed as a sustainable and effective methodology for the generation of polyphenol-enriched extracts from S. fruticosa, which could be used as effective food antioxidants/antimicrobials and/or cosmetic constituents.

ACS Style

Spyros Grigorakis; Abedalghani Halahlah; Dimitris P. Makris. Hydroglycerolic Solvent and Ultrasonication Pretreatment: A Green Blend for High-Efficiency Extraction of Salvia fruticosa Polyphenols. Sustainability 2020, 12, 4840 .

AMA Style

Spyros Grigorakis, Abedalghani Halahlah, Dimitris P. Makris. Hydroglycerolic Solvent and Ultrasonication Pretreatment: A Green Blend for High-Efficiency Extraction of Salvia fruticosa Polyphenols. Sustainability. 2020; 12 (12):4840.

Chicago/Turabian Style

Spyros Grigorakis; Abedalghani Halahlah; Dimitris P. Makris. 2020. "Hydroglycerolic Solvent and Ultrasonication Pretreatment: A Green Blend for High-Efficiency Extraction of Salvia fruticosa Polyphenols." Sustainability 12, no. 12: 4840.

Journal article
Published: 16 May 2020 in Applied Sciences
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S. fruticosa, collectively known as Cretan sage, is a medicinal plant to which a number of bioactivities have been attributed. In spite of its importance in nutrition and pharmacy, reports on the extraction of major polyphenols using sustainable processes are particularly limited. In this study, three common cyclodextrins, namely, methyl β-cyclodextrin (m-β-CD), hydroxypropyl β-cyclodextrin (HP-β-CD), and β-cyclodextrin (β-CD), were tested as green boosters of aqueous extraction of polyphenols from aerial parts of S. fruticosa. To examine simultaneously important extraction parameters, including the concentration of cyclodextrins (CCD), pH, and liquid-to-solid ratio (RL/S), a Box–Behnken design was chosen, with three central points. Temperature effects on the extraction yield were also considered, by carrying out kinetics. The results showed that m-β-CD was the most effective extraction booster, providing total polyphenols yields that amounted to 98.39 mg gallic acid equivalents g−1 dry mass. The kinetic assay demonstrated that extraction was highly effective at 80 °C, increasing significantly polyphenol yield, as well as the ferric-reducing power and antiradical activity of the extracts. It was also proven that extraction with m-β-CD was the least energy-demanding process. Liquid chromatography-tandem mass spectrometry examination revealed that m-β-CD might possess higher affinity for luteolin 7-O-glucuronide extraction, but β-CD for rosmarinic acid extraction.

ACS Style

Spyros Grigorakis; Amina Benchennouf; Abedalghani Halahlah; Dimitris P. Makris. High-Performance Green Extraction of Polyphenolic Antioxidants from Salvia fruticosa Using Cyclodextrins: Optimization, Kinetics, and Composition. Applied Sciences 2020, 10, 3447 .

AMA Style

Spyros Grigorakis, Amina Benchennouf, Abedalghani Halahlah, Dimitris P. Makris. High-Performance Green Extraction of Polyphenolic Antioxidants from Salvia fruticosa Using Cyclodextrins: Optimization, Kinetics, and Composition. Applied Sciences. 2020; 10 (10):3447.

Chicago/Turabian Style

Spyros Grigorakis; Amina Benchennouf; Abedalghani Halahlah; Dimitris P. Makris. 2020. "High-Performance Green Extraction of Polyphenolic Antioxidants from Salvia fruticosa Using Cyclodextrins: Optimization, Kinetics, and Composition." Applied Sciences 10, no. 10: 3447.

Journal article
Published: 01 April 2020 in AgriEngineering
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Olive leaves (OLL) are considered to be a highly appreciated bioresource of bioactive polyphenolic phytochemicals, embracing several different structures. However, extraction processes based on deep eutectic solvents (DES) are very limited despite the wide range of techniques developed for the efficient recovery of polyphenols. This study had as objective the development of a simple, green, high-performance extraction methodology for OLL polyphenols, using a recently reported effective DES, composed of L-lactic acid and glycine. Initially, a screening was performed to select the most appropriate L-lactic/glycine molar ratio and process optimization was then carried out with response surface methodology. The optimized process variable values were DES/water (78% w/v), liquid-to-solid ratio of 36 mL g−1, and stirring speed of 500 rounds per minute, and the total polyphenol yield amounted to 97.53 ± 3.54 mg gallic acid equivalents per g dry matter. Extraction with DES at 80 °C did not significantly increase the total polyphenol yield, but it did enhance the total flavonoid yield and antioxidant activity. High-performance liquid chromatography analyses revealed that extraction with the DES resulted in extended oleuropein hydrolysis, to the favor of hydroxytyrosol formation. This finding might have a prospect in using properly tuned DES for polyphenol modification with improved bioactivities.

ACS Style

Olga Kaltsa; Spyros Grigorakis; Achillia Lakka; Eleni Bozinou; Stavros Lalas; Dimitris P. Makris. Green Valorization of Olive Leaves to Produce Polyphenol-Enriched Extracts Using an Environmentally Benign Deep Eutectic Solvent. AgriEngineering 2020, 2, 226 -239.

AMA Style

Olga Kaltsa, Spyros Grigorakis, Achillia Lakka, Eleni Bozinou, Stavros Lalas, Dimitris P. Makris. Green Valorization of Olive Leaves to Produce Polyphenol-Enriched Extracts Using an Environmentally Benign Deep Eutectic Solvent. AgriEngineering. 2020; 2 (2):226-239.

Chicago/Turabian Style

Olga Kaltsa; Spyros Grigorakis; Achillia Lakka; Eleni Bozinou; Stavros Lalas; Dimitris P. Makris. 2020. "Green Valorization of Olive Leaves to Produce Polyphenol-Enriched Extracts Using an Environmentally Benign Deep Eutectic Solvent." AgriEngineering 2, no. 2: 226-239.

Journal article
Published: 16 March 2020 in Applied Sciences
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The purpose of this study was to evaluate comparatively the polyphenolic content and the antioxidant activity of selected regional red and white wine varieties, produced in the Republic of North Macedonia. The polyphenolic content was evaluated by measuring the total polyphenol, total flavonoid, total tannin and total anthocyanin contents and the antioxidant activity by applying the DPPH (2,2-diphenyl-1-picrylhydrazyl), FRAP (ferric-reducing antioxidant power) and CUPRAC (cupric ion-reducing antioxidant capacity) assays. Statistical analysis of the results showed that all white wines examined (Smederevka, Temjanika and Zhilavka) belong to the same group, two red wines (Vranec and Kratoshija) belong to another group while the Stanushina red variety shows distinct differences from the other red wines examined.

ACS Style

Katerina Mitrevska; Spyros Grigorakis; Sofia Loupassaki; Antony C. Calokerinos. Antioxidant Activity and Polyphenolic Content of North Macedonian Wines. Applied Sciences 2020, 10, 2010 .

AMA Style

Katerina Mitrevska, Spyros Grigorakis, Sofia Loupassaki, Antony C. Calokerinos. Antioxidant Activity and Polyphenolic Content of North Macedonian Wines. Applied Sciences. 2020; 10 (6):2010.

Chicago/Turabian Style

Katerina Mitrevska; Spyros Grigorakis; Sofia Loupassaki; Antony C. Calokerinos. 2020. "Antioxidant Activity and Polyphenolic Content of North Macedonian Wines." Applied Sciences 10, no. 6: 2010.

Journal article
Published: 19 February 2020 in Molecules
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Sambucus nigra flowers, known as elderberry flowers (EBF), are a plant tissue rich in polyphenolic phytochemicals with important bioactivities. However, there are few studies dealing with the production of polyphenol-containing EBF extracts. The objective of the investigation presented herein was the development of a high-performance green extraction methodology, to generate EBF extracts enriched in polyphenolic substances, using an efficient deep eutectic solvent, combined with ultrasonication pretreatment. The DES was composed of L-lactic acid (hydrogen bond donor—HBD) and glycine (hydrogen bond acceptor—HBA) and, after an initial screening to properly regulate HBD/HBA ratio, the extraction was optimized by deploying response surface methodology. Under the optimized conditions, which were DES/water (85% w/v), liquid-to-solid ratio 60 mL g−1, and stirring speed 200 rounds per minute, the extraction yield in total polyphenols amounted to 121.24 ± 8.77 mg gallic acid equivalents per g dry matter. The integration of ultrasonication prior to the batch stirred-tank extraction boosted polyphenol recovery of up to 174.73 ± 2.62 mg gallic acid equivalents per g dry matter. Liquid chromatography–mass spectrometry analysis showed that the richest EBF extract obtained was dominated by rutin, a di-p-coumaroylquic acid and chlorogenic acid.

ACS Style

Olga Kaltsa; Achillia Lakka; Spyros Grigorakis; Ioanna Karageorgou; Georgia Batra; Eleni Bozinou; Stavros Lalas; Dimitris P. Makris. A Green Extraction Process for Polyphenols from Elderberry (Sambucus nigra) Flowers Using Deep Eutectic Solvent and Ultrasound-Assisted Pretreatment. Molecules 2020, 25, 921 .

AMA Style

Olga Kaltsa, Achillia Lakka, Spyros Grigorakis, Ioanna Karageorgou, Georgia Batra, Eleni Bozinou, Stavros Lalas, Dimitris P. Makris. A Green Extraction Process for Polyphenols from Elderberry (Sambucus nigra) Flowers Using Deep Eutectic Solvent and Ultrasound-Assisted Pretreatment. Molecules. 2020; 25 (4):921.

Chicago/Turabian Style

Olga Kaltsa; Achillia Lakka; Spyros Grigorakis; Ioanna Karageorgou; Georgia Batra; Eleni Bozinou; Stavros Lalas; Dimitris P. Makris. 2020. "A Green Extraction Process for Polyphenols from Elderberry (Sambucus nigra) Flowers Using Deep Eutectic Solvent and Ultrasound-Assisted Pretreatment." Molecules 25, no. 4: 921.

Journal article
Published: 27 December 2019 in Applied Sciences
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Moringa oleifera L. leaves are a plant tissue particularly rich in polyphenolic phytochemicals with significant bioactivities, and there has been significant recent interest for the production of extracts enriched in these substances. The current investigation is aimed at establishing a green extraction process, using a novel eco-friendly natural deep eutectic solvent, composed of glycerol and nicotinamide. Furthermore, sample ultrasonication prior to batch stirred-tank extraction was studied to examine its usefulness as a pretreatment step. Optimization of the extraction process through response surface methodology showed that the maximum total polyphenol yield (82.87 ± 4.28 mg gallic acid equivalents g−1 dry mass) could be achieved after a 30 min ultrasonication pretreatment, but the difference with the yield obtained from the non-pretreated sample was statistically non-significant (p < 0.05). Extraction kinetics revealed that the activation energy for the ultrasonication-pretreated samples was more energy-demanding, a fact attributed to phenomena pertaining to washing of the readily extracted polyphenols during pretreatment. Liquid-chromatography-diode array-mass spectrometry showed that ultrasonication pretreatment may have a limited positive effect on polyphenol extractability, but the overall polyphenolic profile was identical for the ultrasonication-pretreated and non-pretreated samples.

ACS Style

Achillia Lakka; Spyros Grigorakis; Olga Kaltsa; Ioanna Karageorgou; Georgia Batra; Eleni Bozinou; Stavros Lalas; Dimitris P. Makris. The Effect of Ultrasonication Pretreatment on the Production of Polyphenol-Enriched Extracts from Moringa oleifera L. (Drumstick Tree) Using a Novel Bio-Based Deep Eutectic Solvent. Applied Sciences 2019, 10, 220 .

AMA Style

Achillia Lakka, Spyros Grigorakis, Olga Kaltsa, Ioanna Karageorgou, Georgia Batra, Eleni Bozinou, Stavros Lalas, Dimitris P. Makris. The Effect of Ultrasonication Pretreatment on the Production of Polyphenol-Enriched Extracts from Moringa oleifera L. (Drumstick Tree) Using a Novel Bio-Based Deep Eutectic Solvent. Applied Sciences. 2019; 10 (1):220.

Chicago/Turabian Style

Achillia Lakka; Spyros Grigorakis; Olga Kaltsa; Ioanna Karageorgou; Georgia Batra; Eleni Bozinou; Stavros Lalas; Dimitris P. Makris. 2019. "The Effect of Ultrasonication Pretreatment on the Production of Polyphenol-Enriched Extracts from Moringa oleifera L. (Drumstick Tree) Using a Novel Bio-Based Deep Eutectic Solvent." Applied Sciences 10, no. 1: 220.

Journal article
Published: 25 November 2019 in Antioxidants
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The current investigation was undertaken to examine saffron processing waste (SPW) as a bioresource, which could be valorized to produce extracts rich in antioxidant polyphenols, using a green, natural deep eutectic solvent (DES). Initially, there was an appraisal of the molar ratio of hydrogen bond donor/hydrogen bond acceptor in order to come up with the most efficient DES composed of L-lactic acid/glycine (5:1). The following step was the optimization of the extraction process using response surface methodology. The optimal conditions thus determined were a DES concentration of 55% (w/v), a liquid-to-solid ratio of 60 mL g−1, and a stirring speed of 800 rounds per minute. Under these conditions, the extraction yield in total polyphenols achieved was 132.43 ± 10.63 mg gallic acid equivalents per g of dry mass. The temperature assay performed within a range of 23 to 80 °C, suggested that extracts displayed maximum yield and antioxidant activity at 50–60 °C. Liquid chromatography-mass spectrometry analysis of the SPW extract obtained under optimal conditions showed that the predominant flavonol was kaempferol 3-O-sophoroside and the major anthocyanin delphinidin 3,5-di-O-glucoside. The results indicated that SPW extraction with the DES used is a green and efficient methodology and may afford extracts rich flavonols and anthocyanins, which are considered to be powerful antioxidants.

ACS Style

Achillia Lakka; Spyros Grigorakis; Ioanna Karageorgou; Georgia Batra; Olga Kaltsa; Eleni Bozinou; Stavros Lalas; Dimitris P. Makris. Saffron Processing Wastes as a Bioresource of High-Value Added Compounds: Development of a Green Extraction Process for Polyphenol Recovery Using a Natural Deep Eutectic Solvent. Antioxidants 2019, 8, 586 .

AMA Style

Achillia Lakka, Spyros Grigorakis, Ioanna Karageorgou, Georgia Batra, Olga Kaltsa, Eleni Bozinou, Stavros Lalas, Dimitris P. Makris. Saffron Processing Wastes as a Bioresource of High-Value Added Compounds: Development of a Green Extraction Process for Polyphenol Recovery Using a Natural Deep Eutectic Solvent. Antioxidants. 2019; 8 (12):586.

Chicago/Turabian Style

Achillia Lakka; Spyros Grigorakis; Ioanna Karageorgou; Georgia Batra; Olga Kaltsa; Eleni Bozinou; Stavros Lalas; Dimitris P. Makris. 2019. "Saffron Processing Wastes as a Bioresource of High-Value Added Compounds: Development of a Green Extraction Process for Polyphenol Recovery Using a Natural Deep Eutectic Solvent." Antioxidants 8, no. 12: 586.

Journal article
Published: 01 October 2018 in ChemEngineering
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This study aimed at investigating the effect of l-ascorbic acid on the Cu2+-induced oxidation of quercetin, within a pH range from 6.7 to 8.3 and temperatures varying from 53 to 87 °C. Initial examinations showed that quercetin degradation obeyed apparent first-order kinetics and it was significantly affected by temperature. Modelling of the effect of l-ascorbic acid by implementing response surface methodology suggested that l-ascorbic acid did not impact quercetin oxidation significantly (p < 0.05) and led to an empirical kinetic model based on temperature (T) and pH. Liquid chromatography–diode array–mass spectrometry analyses revealed the presence of typical quercetin degradation and oxidation products, including protocatechuic acid and 2-(hydroxybenzoyl)-2-hydroxybenzofuran-3(2H)-one. It was concluded that the formation of l-ascorbyl or other radicals (superoxide anion) may be involved in quercetin oxidation and this fact merits further attention to illuminate the possible beneficial or adverse nutritional consequences of such reactions in foods.

ACS Style

Nikoletta Bobolaki; Angelos Photiades; Spyros Grigorakis; Dimitris P. Makris. Empirical Kinetic Modelling of the Effect of l-Ascorbic Acid on the Cu(II)-Induced Oxidation of Quercetin. ChemEngineering 2018, 2, 46 .

AMA Style

Nikoletta Bobolaki, Angelos Photiades, Spyros Grigorakis, Dimitris P. Makris. Empirical Kinetic Modelling of the Effect of l-Ascorbic Acid on the Cu(II)-Induced Oxidation of Quercetin. ChemEngineering. 2018; 2 (4):46.

Chicago/Turabian Style

Nikoletta Bobolaki; Angelos Photiades; Spyros Grigorakis; Dimitris P. Makris. 2018. "Empirical Kinetic Modelling of the Effect of l-Ascorbic Acid on the Cu(II)-Induced Oxidation of Quercetin." ChemEngineering 2, no. 4: 46.

Journal article
Published: 15 August 2018 in Chemical Engineering Communications
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ACS Style

Zaher Slim; Magdalena Jancheva; Spyros Grigorakis; Dimitris P. Makris. Polyphenol extraction from Origanum dictamnus using low-transition temperature mixtures composed of glycerol and organic salts: Effect of organic anion carbon chain length. Chemical Engineering Communications 2018, 205, 1494 -1506.

AMA Style

Zaher Slim, Magdalena Jancheva, Spyros Grigorakis, Dimitris P. Makris. Polyphenol extraction from Origanum dictamnus using low-transition temperature mixtures composed of glycerol and organic salts: Effect of organic anion carbon chain length. Chemical Engineering Communications. 2018; 205 (10):1494-1506.

Chicago/Turabian Style

Zaher Slim; Magdalena Jancheva; Spyros Grigorakis; Dimitris P. Makris. 2018. "Polyphenol extraction from Origanum dictamnus using low-transition temperature mixtures composed of glycerol and organic salts: Effect of organic anion carbon chain length." Chemical Engineering Communications 205, no. 10: 1494-1506.

Research article
Published: 02 August 2018 in ELECTROPHORESIS
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The valorization of onion (Allium cepa) solid wastes, a 450,000 tonnes/year waste in Europe, by a green extraction method is presented. Polyphenols of onion solid wastes were extracted using eco‐friendly solvents, such as water and glycerol. The 2‐hydroxypropyl‐β‐cyclodextrin was also used as a co‐solvent for the augmentation of the extraction yield. The process has been optimized by implementing a central composite face centered design of experiments, with two replicates in the central point, taking into consideration the following independent variables: glycerol concentration, cyclodextrin concentration and temperature. The assessment of the extraction model was based on two responses: the total pigment yield and the antiradical capacity. LC‐MS analysis was also employed in order to identify polyphenols and colourants of the obtained extracts. The main polyphenols found were quercetin and quercetin derivatives and the main colourant was cyanidin 3‐O‐glucoside. The extract was also tested as a food colourant in a yoghurt matrix. The onion leaf extract was found to be a stable natural colourant and could be utilized as an alternative ingredient to synthetic coloring agents. This article is protected by copyright. All rights reserved

ACS Style

Ioannis Mourtzinos; Prodromos Prodromidis; Spyros Grigorakis; Dimitris P. Makris; Costas Biliaderis; Thomas Moschakis. Natural food colorants derived from onion wastes: Application in a yoghurt product. ELECTROPHORESIS 2018, 39, 1975 -1983.

AMA Style

Ioannis Mourtzinos, Prodromos Prodromidis, Spyros Grigorakis, Dimitris P. Makris, Costas Biliaderis, Thomas Moschakis. Natural food colorants derived from onion wastes: Application in a yoghurt product. ELECTROPHORESIS. 2018; 39 (15):1975-1983.

Chicago/Turabian Style

Ioannis Mourtzinos; Prodromos Prodromidis; Spyros Grigorakis; Dimitris P. Makris; Costas Biliaderis; Thomas Moschakis. 2018. "Natural food colorants derived from onion wastes: Application in a yoghurt product." ELECTROPHORESIS 39, no. 15: 1975-1983.

Journal article
Published: 01 July 2018 in Nova Biotechnologica et chimica
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Polyphenol extracts from Moringa oleifera leaves (MoL) were obtained with a glycerol-based low-transition temperature mixture (LTTM) and a combination of LTTM with 2-hydroxypropyl β-cyclodextrin (HP-β-CD). The extracts were maintained at 4, 22 and 50 °C for 18 days and the antiradical activity (AAR) was recorded to detect modifications in the antioxidant activity of the extracts. AAR displayed a constant decline at every temperature tested, following pseudo first-order kinetics and the decay constants suggested that the presence of HP-β-CD had a protective action, slowing down AAR decline. The analysis of the polyphenolic profiles using liquid chromatography-diode array-mass spectrometry revealed that after storage for 18 days at 50 °C, the major quercetin glycosides occurring in MoL were extensively degraded. Based on the detection of protocatechuic acid in the stored extracts, putative pathways of flavonol glycoside degradation were proposed. It was concluded that the decomposition of these components was mainly responsible for the AAR decline observed.

ACS Style

Ioanna Karageorgou; Spyros Grigorakis; Stavros Lalas; Dimitris P. Makris. The effect of 2-hydroxypropyl β-cyclodextrin on the stability of polyphenolic compounds from Moringa oleifera Lam leaf extracts in a natural low-transition temperature mixture. Nova Biotechnologica et chimica 2018, 17, 29 -37.

AMA Style

Ioanna Karageorgou, Spyros Grigorakis, Stavros Lalas, Dimitris P. Makris. The effect of 2-hydroxypropyl β-cyclodextrin on the stability of polyphenolic compounds from Moringa oleifera Lam leaf extracts in a natural low-transition temperature mixture. Nova Biotechnologica et chimica. 2018; 17 (1):29-37.

Chicago/Turabian Style

Ioanna Karageorgou; Spyros Grigorakis; Stavros Lalas; Dimitris P. Makris. 2018. "The effect of 2-hydroxypropyl β-cyclodextrin on the stability of polyphenolic compounds from Moringa oleifera Lam leaf extracts in a natural low-transition temperature mixture." Nova Biotechnologica et chimica 17, no. 1: 29-37.

Communication
Published: 27 January 2018 in Medicines
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Background: The aromatic plant Stachys mucronata (Lamiaceae) is endemic to the island of Crete (southern Greece), but as opposed to other native Greek members of this family, this species has never been investigated in the past with regard to its polyphenolic composition and antioxidant potency. Methods: Aerial parts of S. mucronata were exhaustively extracted and partly fractionated through partition, using n-butanol and dichloromethane. Results: Following an initial examination, which consisted of estimating the total polyphenol content and the antiradical activity, the n-butanol extract was found to be by far the richest in polyphenols, exhibiting much stronger antiradical activity compared with the dichloromethane counterpart. On this basis, the n-butanol extract was analysed by liquid chromatography-diode array-mass spectrometry, to tentatively characterise the principal polyphenolic components, which were shown to be flavonol but mainly flavone derivatives. Conclusions: The most potent radical-scavenging compounds were detected in the n-butanol fraction of the extracts, suggesting that the most active antioxidants in S. mucronate are relatively polar. The analyses suggested the major constituents to be derivatives of the flavone luteolin, accompanied by apigenin analogues, as well as flavonol glycosides and chlorogenate conjugates.

ACS Style

Spyros Grigorakis; Dimitris P. Makris. Characterisation of Polyphenol-Containing Extracts from Stachys mucronata and Evaluation of Their Antiradical Activity. Medicines 2018, 5, 14 .

AMA Style

Spyros Grigorakis, Dimitris P. Makris. Characterisation of Polyphenol-Containing Extracts from Stachys mucronata and Evaluation of Their Antiradical Activity. Medicines. 2018; 5 (1):14.

Chicago/Turabian Style

Spyros Grigorakis; Dimitris P. Makris. 2018. "Characterisation of Polyphenol-Containing Extracts from Stachys mucronata and Evaluation of Their Antiradical Activity." Medicines 5, no. 1: 14.

Journal article
Published: 01 September 2017 in Journal of Applied Research on Medicinal and Aromatic Plants
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ACS Style

Magdalena Jancheva; Spyros Grigorakis; Sofia Loupassaki; Dimitris P. Makris. Optimised extraction of antioxidant polyphenols from Satureja thymbra using newly designed glycerol-based natural low-transition temperature mixtures (LTTMs). Journal of Applied Research on Medicinal and Aromatic Plants 2017, 6, 31 -40.

AMA Style

Magdalena Jancheva, Spyros Grigorakis, Sofia Loupassaki, Dimitris P. Makris. Optimised extraction of antioxidant polyphenols from Satureja thymbra using newly designed glycerol-based natural low-transition temperature mixtures (LTTMs). Journal of Applied Research on Medicinal and Aromatic Plants. 2017; 6 ():31-40.

Chicago/Turabian Style

Magdalena Jancheva; Spyros Grigorakis; Sofia Loupassaki; Dimitris P. Makris. 2017. "Optimised extraction of antioxidant polyphenols from Satureja thymbra using newly designed glycerol-based natural low-transition temperature mixtures (LTTMs)." Journal of Applied Research on Medicinal and Aromatic Plants 6, no. : 31-40.

Original paper
Published: 13 April 2017 in European Food Research and Technology
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In this study, the extraction of polyphenols from Moringa oleifera leaves was investigated, using a biomolecule-based low-transition temperature mixture (LTTM), composed of glycerol and sodium acetate. The first step was to optimise LTTM concentration (CLTTM) and the molar ratio (Rmol) of glycerol-to-sodium acetate, by employing a Box–Behnken experimental design. Following this, a kinetic assay was undertaken to assess the effect of temperature. A maximum yield in total polyphenols (YTP = 53.80 mg gallic acid equivalents per g lyophilised material) was achieved using a CLTTM = 80% (w/v) and a Rmol = 6. The extraction followed a second-order model, requiring activation energy (Ea) of 55.71 kJ mol−1. Comparative evaluation using 80% ethanol showed that the LTTM used was significantly more efficient in extracting polyphenols and flavonoids, yielding extracts with higher reducing power. However, results concerning the antiradical activity were contradictory. Liquid chromatography–diode array–mass spectrometry examination of both the LTTM and the hydroalcoholic extracts revealed some qualitative differences, which might indicate selectivity of the LTTM towards relatively polar substances.

ACS Style

Ioanna Karageorgou; Spyros Grigorakis; Stavros Lalas; Dimitris P. Makris. Enhanced extraction of antioxidant polyphenols from Moringa oleifera Lam. leaves using a biomolecule-based low-transition temperature mixture. European Food Research and Technology 2017, 243, 1839 -1848.

AMA Style

Ioanna Karageorgou, Spyros Grigorakis, Stavros Lalas, Dimitris P. Makris. Enhanced extraction of antioxidant polyphenols from Moringa oleifera Lam. leaves using a biomolecule-based low-transition temperature mixture. European Food Research and Technology. 2017; 243 (10):1839-1848.

Chicago/Turabian Style

Ioanna Karageorgou; Spyros Grigorakis; Stavros Lalas; Dimitris P. Makris. 2017. "Enhanced extraction of antioxidant polyphenols from Moringa oleifera Lam. leaves using a biomolecule-based low-transition temperature mixture." European Food Research and Technology 243, no. 10: 1839-1848.

Journal article
Published: 05 April 2017 in Environments
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Olive leaves (OLL) represent a major waste generated during the production of olive oil, but there is a great potential for their valorization, because they provide important content in polyphenolic phytochemicals, which possess several bioactivities. In spite of the high number of studies dealing with polyphenol recovery from olive leaves, green processes involving environmentally benign solvents are scarce. In this study, a novel renewable natural low-transition temperature mixture (LTTM), composed of glycerol and sodium-potassium tartrate, was tested for its efficient ability to extract polyphenolic substances from OLL. The extraction process was optimised by using response surface methodology and the maximum yield in total polyphenols was 26.75 ± 3.22 mg caffeic acid equivalents per g dry weight, achieved with 50% (v/v) aqueous LTTM, liquid-to-solid ratio of 45 mL g−1 and at 73 °C. The LTTM was proven to be equally effective with 60% aqueous methanol, but it displayed inferior antioxidant properties. Liquid chromatography-diode array-mass spectrometry analyses revealed no significant qualitative differences between the LTTM and the aqueous methanolic extract.

ACS Style

Marianna Dedousi; Valentina Mamoudaki; Spyros Grigorakis; Dimitris P. Makris. Ultrasound-Assisted Extraction of Polyphenolic Antioxidants from Olive (Olea europaea) Leaves Using a Novel Glycerol/Sodium-Potassium Tartrate Low-Transition Temperature Mixture (LTTM). Environments 2017, 4, 31 .

AMA Style

Marianna Dedousi, Valentina Mamoudaki, Spyros Grigorakis, Dimitris P. Makris. Ultrasound-Assisted Extraction of Polyphenolic Antioxidants from Olive (Olea europaea) Leaves Using a Novel Glycerol/Sodium-Potassium Tartrate Low-Transition Temperature Mixture (LTTM). Environments. 2017; 4 (2):31.

Chicago/Turabian Style

Marianna Dedousi; Valentina Mamoudaki; Spyros Grigorakis; Dimitris P. Makris. 2017. "Ultrasound-Assisted Extraction of Polyphenolic Antioxidants from Olive (Olea europaea) Leaves Using a Novel Glycerol/Sodium-Potassium Tartrate Low-Transition Temperature Mixture (LTTM)." Environments 4, no. 2: 31.

Journal article
Published: 18 June 2016 in Recycling
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A novel natural low transition temperature mixture (LTTM), composed of glycerol and ammonium acetate (molar ratio 3:1), was tested for its efficacy as a solvent in recovering phenolics from chlorogenate-rich agri-food solid wastes, including potato peels (PPs), eggplant peels (EPPs), and spent filter coffee (SFC). The efficacy of this solvent was compared with other eco-friendly solvents, including aqueous glycerol, aqueous ethanol, and water. The LTTM was demonstrated to be by far the most efficient in extracting chlorogenates and superior or equally efficient with the other solvents in recovering flavonoids. LTTM extracts produced from waste were also more potent radical scavengers, but results on the reducing power were inconclusive. Liquid chromatography-diode array-mass spectrometry analysis showed that the polyphenolic profiles of all waste extracts obtained with the LTTM were rich in caffeoylquinic and p-coumaroylquinic acid conjugates.

ACS Style

Areti Manousaki; Magdalena Jancheva; Spyros Grigorakis; Dimitris P. Makris. Extraction of Antioxidant Phenolics from Agri-Food Waste Biomass Using a Newly Designed Glycerol-Based Natural Low-Transition Temperature Mixture: A Comparison with Conventional Eco-Friendly Solvents. Recycling 2016, 1, 194 -204.

AMA Style

Areti Manousaki, Magdalena Jancheva, Spyros Grigorakis, Dimitris P. Makris. Extraction of Antioxidant Phenolics from Agri-Food Waste Biomass Using a Newly Designed Glycerol-Based Natural Low-Transition Temperature Mixture: A Comparison with Conventional Eco-Friendly Solvents. Recycling. 2016; 1 (1):194-204.

Chicago/Turabian Style

Areti Manousaki; Magdalena Jancheva; Spyros Grigorakis; Dimitris P. Makris. 2016. "Extraction of Antioxidant Phenolics from Agri-Food Waste Biomass Using a Newly Designed Glycerol-Based Natural Low-Transition Temperature Mixture: A Comparison with Conventional Eco-Friendly Solvents." Recycling 1, no. 1: 194-204.

Journal article
Published: 01 December 2015 in Industrial Crops and Products
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Onion solid wastes (OSW) were used as raw material to produce polyphenol- and pigment-enriched extracts with antioxidant activity, using ultrasound-assisted solid-liquid extraction. The extraction medium used was free from conventional volatile organic solvents, and it was composed of water and glycerol. Glycerol concentration (Cgl) and liquid-to-solid ratio (RL/S) were first optimised employing Box–Behnken experimental design and then extraction efficiency was further assessed through kinetics. The optimal conditions were found to be Cgl = 90% (w/v) and RL/S = 90 mL g−1, and under these conditions the extraction of total polyphenols and total pigments was shown to obey first-order kinetics. Maximal effective diffusion (De) values were 9.28 × 10−11 and 13.22 × 10−11 m2 s−1, for total polyphenols and total pigments, respectively, while the corresponding activation energies (Ea) were 31.52 and 12.11 kJ mol−1. The reducing power (PR) increased as a response to increasing extraction temperature and the extract obtained at 80 °C had PR value of 490 μmol ascorbic acid equivalents per g of dry weight. Liquid chromatography-diode array-mass spectrometry analysis of this extract showed that the major polyphenols tentatively identified were quercetin 4′-O-glucoside and quercetin, accompanied by other quercetin glycosides, cyaniding 3-O-glucoside and a series of quercetin degradation and oxidation products.

ACS Style

Photene Katsampa; Evdokea Valsamedou; Spyros Grigorakis; Dimitris P. Makris. A green ultrasound-assisted extraction process for the recovery of antioxidant polyphenols and pigments from onion solid wastes using Box–Behnken experimental design and kinetics. Industrial Crops and Products 2015, 77, 535 -543.

AMA Style

Photene Katsampa, Evdokea Valsamedou, Spyros Grigorakis, Dimitris P. Makris. A green ultrasound-assisted extraction process for the recovery of antioxidant polyphenols and pigments from onion solid wastes using Box–Behnken experimental design and kinetics. Industrial Crops and Products. 2015; 77 ():535-543.

Chicago/Turabian Style

Photene Katsampa; Evdokea Valsamedou; Spyros Grigorakis; Dimitris P. Makris. 2015. "A green ultrasound-assisted extraction process for the recovery of antioxidant polyphenols and pigments from onion solid wastes using Box–Behnken experimental design and kinetics." Industrial Crops and Products 77, no. : 535-543.

Journal article
Published: 01 July 2015 in Separation and Purification Technology
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ACS Style

Emad Shehata; Spyros Grigorakis; Sofia Loupassaki; Dimitris P. Makris. Extraction optimisation using water/glycerol for the efficient recovery of polyphenolic antioxidants from two Artemisia species. Separation and Purification Technology 2015, 149, 462 -469.

AMA Style

Emad Shehata, Spyros Grigorakis, Sofia Loupassaki, Dimitris P. Makris. Extraction optimisation using water/glycerol for the efficient recovery of polyphenolic antioxidants from two Artemisia species. Separation and Purification Technology. 2015; 149 ():462-469.

Chicago/Turabian Style

Emad Shehata; Spyros Grigorakis; Sofia Loupassaki; Dimitris P. Makris. 2015. "Extraction optimisation using water/glycerol for the efficient recovery of polyphenolic antioxidants from two Artemisia species." Separation and Purification Technology 149, no. : 462-469.