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Vassilios P Papageorgiou - One of the best experts on this subject based on the ideXlab platform.
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Electrospun fiber mats containing shikonin and derivatives with potential biomedical applications.
International journal of pharmaceutics, 2011Co-Authors: Konstantinos N Kontogiannopoulos, Andreana N Assimopoulou, Ioannis Tsivintzelis, Costas Panayiotou, Vassilios P PapageorgiouAbstract:Alkannin, shikonin (A/S) and their derivatives are naturally occurring hydroxynaphthoquinones with a well-established spectrum of wound healing, antimicrobial, anti-inflammatory, antioxidant and antitumor activity. Clinical studies over the years revealed that A/S derivatives-based wound healing preparations (such as HELIXDERM(®)) are among a very small group of therapeutics that modulate both the inflammatory and proliferative phases of wound healing and present significant tissue regenerative activity. The purpose of the present work was to combine the biological properties of A/S and the advantages of electrospun meshes to prepare a potent topical/transdermal biomaterial for A/S. Four biocompatible polymers (cellulose acetate, poly(L-lactide), poly(lactide-co-glycolide) LA/GA:50/50 and 75/25) were used for the first time, to produce electrospun fiber mats containing either shikonin or A/S mixture in various amounts. Both drugs were effectively loaded into the above biomaterials. The incorporation of drugs did not considerably affect fibers morphology and their mean diameter size varied from 315 to 670 nm. High drug entrapment efficiencies (ranged from 74% to 95%) and appropriate release profiles were achieved, that render these fibers as potential A/S topical/transdermal wound healing dressings. Given the multifunctional activity of the natural products Alkannins and shikonins, their consideration as bioactive constituents for tissue engineering scaffolds seems a promising strategy for repairing and regenerating tissues and mainly skin.
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Structure-radical scavenging activity relationship of Alkannin/shikonin derivatives
Food Chemistry, 2011Co-Authors: Stella A. Ordoudi, Andreana N Assimopoulou, Stella Tsermentseli, Nikolaos Nenadis, Maria Z. Tsimidou, Vassilios P PapageorgiouAbstract:Alkannins and shikonins (A/S) are naturally occurring isohexenylnaphthazarins (IHNs) of great interest in the field of life sciences due to their broad spectrum of biological properties and are used as food colourants in some countries. In the present study for the first time assessment of the radical scavenging activity of A/S and selected derivatives was carried out using the Crocin Bleaching Assay (CBA) and a modified DPPH assay. Exploration of structure-radical scavenging activity relationship (SAR) was approached with a wide range of A/S derivatives. To accomplish this task, a computational approach was also employed for the two enantiomers and other structurally related compounds. The findings indicated that the side chain –OH group at C-1′ has a positive effect to the radical scavenging properties of Alkannin/shikonin by assisting hydrogen atom donation from this carbon atom. Thus, Alkannin and shikonin were more potent than deoxyshikonin. Esterification of that hydroxyl group was critical for the activity of the respective compounds (acetyl-, isovaleryl- and β,β-dimethylacryl-shikonin). All of the examined IHN derivatives were found experimentally less potent scavengers than naphthazarin.
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structure radical scavenging activity relationship of Alkannin shikonin derivatives
Food Chemistry, 2011Co-Authors: Stella A. Ordoudi, Stella Tsermentseli, Nikolaos Nenadis, Maria Z. Tsimidou, A N Assimopoulou, Vassilios P PapageorgiouAbstract:Alkannins and shikonins (A/S) are naturally occurring isohexenylnaphthazarins (IHNs) of great interest in the field of life sciences due to their broad spectrum of biological properties and are used as food colourants in some countries. In the present study for the first time assessment of the radical scavenging activity of A/S and selected derivatives was carried out using the Crocin Bleaching Assay (CBA) and a modified DPPH assay. Exploration of structure-radical scavenging activity relationship (SAR) was approached with a wide range of A/S derivatives. To accomplish this task, a computational approach was also employed for the two enantiomers and other structurally related compounds. The findings indicated that the side chain –OH group at C-1′ has a positive effect to the radical scavenging properties of Alkannin/shikonin by assisting hydrogen atom donation from this carbon atom. Thus, Alkannin and shikonin were more potent than deoxyshikonin. Esterification of that hydroxyl group was critical for the activity of the respective compounds (acetyl-, isovaleryl- and β,β-dimethylacryl-shikonin). All of the examined IHN derivatives were found experimentally less potent scavengers than naphthazarin.
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preparative isolation and purification of Alkannin shikonin derivatives from natural products by high speed counter current chromatography
Biomedical Chromatography, 2009Co-Authors: A N Assimopoulou, Hermann Stuppner, Sonja Sturm, Vassilios P PapageorgiouAbstract:Alkannin and shikonin (A/S) and their derivatives have been found in the roots of several Boraginaceous species and are also produced through plant tissue cultures. The chiral compounds A/S are potent pharmaceutical substances with a wide spectrum of biological and pharmacological activities like wound healing, antimicrobial, anti-inflammatory, anticancer and antioxidant activity. High-speed counter-current chromatography (HSCCC) was applied for the first time to the separation, preparative isolation and purification of A/S and their esters from extracts of Alkanna tinctoria roots, as well as commercial samples. The constituents of HSCCC fractions and their purity were determined by high-performance liquid chromatography-diode array detection-mass spectrometry (HPLC-DAD-MS), since DAD cannot detect oligomeric A/S derivatives that are present in most of the samples containing the respective monomeric derivatives. The purity of HSCCC fractions was compared with the one of fractions isolated by column chromatography (CC) using as stationary phases silica gel and Sephadex LH-20. As shown, the purity of monomeric Alkannin/shikonin was greater by HSCCC than CC separation of commercial A/S samples.
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Preparative isolation and purification of Alkannin/shikonin derivatives from natural products by high-speed counter-current chromatography.
Biomedical chromatography : BMC, 2009Co-Authors: Andreana N Assimopoulou, Hermann Stuppner, Sonja Sturm, Vassilios P PapageorgiouAbstract:Alkannin and shikonin (A/S) and their derivatives have been found in the roots of several Boraginaceous species and are also produced through plant tissue cultures. The chiral compounds A/S are potent pharmaceutical substances with a wide spectrum of biological and pharmacological activities like wound healing, antimicrobial, anti-inflammatory, anticancer and antioxidant activity. High-speed counter-current chromatography (HSCCC) was applied for the first time to the separation, preparative isolation and purification of A/S and their esters from extracts of Alkanna tinctoria roots, as well as commercial samples. The constituents of HSCCC fractions and their purity were determined by high-performance liquid chromatography-diode array detection-mass spectrometry (HPLC-DAD-MS), since DAD cannot detect oligomeric A/S derivatives that are present in most of the samples containing the respective monomeric derivatives. The purity of HSCCC fractions was compared with the one of fractions isolated by column chromatography (CC) using as stationary phases silica gel and Sephadex LH-20. As shown, the purity of monomeric Alkannin/shikonin was greater by HSCCC than CC separation of commercial A/S samples.
Andreana N Assimopoulou - One of the best experts on this subject based on the ideXlab platform.
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Electrospun fiber mats containing shikonin and derivatives with potential biomedical applications.
International journal of pharmaceutics, 2011Co-Authors: Konstantinos N Kontogiannopoulos, Andreana N Assimopoulou, Ioannis Tsivintzelis, Costas Panayiotou, Vassilios P PapageorgiouAbstract:Alkannin, shikonin (A/S) and their derivatives are naturally occurring hydroxynaphthoquinones with a well-established spectrum of wound healing, antimicrobial, anti-inflammatory, antioxidant and antitumor activity. Clinical studies over the years revealed that A/S derivatives-based wound healing preparations (such as HELIXDERM(®)) are among a very small group of therapeutics that modulate both the inflammatory and proliferative phases of wound healing and present significant tissue regenerative activity. The purpose of the present work was to combine the biological properties of A/S and the advantages of electrospun meshes to prepare a potent topical/transdermal biomaterial for A/S. Four biocompatible polymers (cellulose acetate, poly(L-lactide), poly(lactide-co-glycolide) LA/GA:50/50 and 75/25) were used for the first time, to produce electrospun fiber mats containing either shikonin or A/S mixture in various amounts. Both drugs were effectively loaded into the above biomaterials. The incorporation of drugs did not considerably affect fibers morphology and their mean diameter size varied from 315 to 670 nm. High drug entrapment efficiencies (ranged from 74% to 95%) and appropriate release profiles were achieved, that render these fibers as potential A/S topical/transdermal wound healing dressings. Given the multifunctional activity of the natural products Alkannins and shikonins, their consideration as bioactive constituents for tissue engineering scaffolds seems a promising strategy for repairing and regenerating tissues and mainly skin.
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Structure-radical scavenging activity relationship of Alkannin/shikonin derivatives
Food Chemistry, 2011Co-Authors: Stella A. Ordoudi, Andreana N Assimopoulou, Stella Tsermentseli, Nikolaos Nenadis, Maria Z. Tsimidou, Vassilios P PapageorgiouAbstract:Alkannins and shikonins (A/S) are naturally occurring isohexenylnaphthazarins (IHNs) of great interest in the field of life sciences due to their broad spectrum of biological properties and are used as food colourants in some countries. In the present study for the first time assessment of the radical scavenging activity of A/S and selected derivatives was carried out using the Crocin Bleaching Assay (CBA) and a modified DPPH assay. Exploration of structure-radical scavenging activity relationship (SAR) was approached with a wide range of A/S derivatives. To accomplish this task, a computational approach was also employed for the two enantiomers and other structurally related compounds. The findings indicated that the side chain –OH group at C-1′ has a positive effect to the radical scavenging properties of Alkannin/shikonin by assisting hydrogen atom donation from this carbon atom. Thus, Alkannin and shikonin were more potent than deoxyshikonin. Esterification of that hydroxyl group was critical for the activity of the respective compounds (acetyl-, isovaleryl- and β,β-dimethylacryl-shikonin). All of the examined IHN derivatives were found experimentally less potent scavengers than naphthazarin.
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Preparative isolation and purification of Alkannin/shikonin derivatives from natural products by high-speed counter-current chromatography.
Biomedical chromatography : BMC, 2009Co-Authors: Andreana N Assimopoulou, Hermann Stuppner, Sonja Sturm, Vassilios P PapageorgiouAbstract:Alkannin and shikonin (A/S) and their derivatives have been found in the roots of several Boraginaceous species and are also produced through plant tissue cultures. The chiral compounds A/S are potent pharmaceutical substances with a wide spectrum of biological and pharmacological activities like wound healing, antimicrobial, anti-inflammatory, anticancer and antioxidant activity. High-speed counter-current chromatography (HSCCC) was applied for the first time to the separation, preparative isolation and purification of A/S and their esters from extracts of Alkanna tinctoria roots, as well as commercial samples. The constituents of HSCCC fractions and their purity were determined by high-performance liquid chromatography-diode array detection-mass spectrometry (HPLC-DAD-MS), since DAD cannot detect oligomeric A/S derivatives that are present in most of the samples containing the respective monomeric derivatives. The purity of HSCCC fractions was compared with the one of fractions isolated by column chromatography (CC) using as stationary phases silica gel and Sephadex LH-20. As shown, the purity of monomeric Alkannin/shikonin was greater by HSCCC than CC separation of commercial A/S samples.
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Simultaneous determination of monomeric and oligomeric Alkannins and shikonins by high-performance liquid chromatography-diode array detection-mass spectrometry.
Biomedical chromatography : BMC, 2008Co-Authors: Andreana N Assimopoulou, Markus Ganzera, Hermann Stuppner, V. P. PapageorgiouAbstract:Alkannin and shikonin (A/S) derivatives have been found in the roots of several Boraginaceous species and are produced through plant tissue cultures. The chiral compounds Alkannins and shikonins are potent pharmaceutical substances with a wide spectrum of pharmacological activities such as wound healing, antimicrobial, anti-inflammatory, anticancer and antioxidant. Although oligomeric A/S derivatives have been detected in root extracts and commercial samples their detection and determination through high-performance liquid chromatography has not been reported. Therefore, in the present study a rapid, simple high-performance liquid chromatography–diode array detection–mass spectrometry (HPLC-DAD-MS) method was developed to detect, separate and determine monomeric and oligomeric/polymeric derivatives of Alkannin/shikonin simultaneously for the first time. An optimization of HPLC-DAD parameters was performed. Both atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) modes were applied, in order to compare detection of monomeric and oligomeric A/S. Additionally, oligomeric A/S constituents in several samples were identified and the mode of A/S polymerization was proposed. Copyright © 2007 John Wiley & Sons, Ltd.
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Analysis of Alkannin derivatives from Alkanna species by high-performance liquid chromatography/photodiode array/mass spectrometry.
Biomedical chromatography : BMC, 2006Co-Authors: Andreana N Assimopoulou, Ioannis Karapanagiotis, A. Vasiliou, Stella Kokkini, V. P. PapageorgiouAbstract:Alkannin, shikonin (A/S) and their derivatives are enantiomeric hydroxynaphthoquinone red pigments found in the roots of almost 150 species of the Boraginaceae family. A/S have been shown to exhibit strong wound healing, antimicrobial, anti-inflammatory and antioxidant activities and recent extensive research has well established their antitumor properties. A/S and their derivatives comprise the active ingredients of several pharmaceutical and cosmetic preparations. Although A/S have been efficiently synthesized and have been produced by cell tissue cultures in high yield, most of the pharmaceutical preparations worldwide contain A/S extracted from the roots of Boraginaceous species, found in nature. In the present study, a high-performance liquid chromatography/photodiode array/mass spectrometry (HPLC/PDA/MS) method was established to identify monomeric hydroxynaphthoquinones of the Alkannin series and other metabolites from Boraginaceous root extracts. This method can be applied for the identification of Alkannin derivatives and other metabolites from Boraginaceous cell cultures, and also to determine active ingredients in pharmaceutical preparations containing A/S derivatives. A phytochemical investigation of the Alkanna genus grown in Greece was also performed. Fifty-three root samples belonging to 10 species of the genus Alkanna (A. calliensis, A. corcyrensis, A. graeca, A. methanaea, A. orientalis, A. pindicola, A. primuliflora, A. sieberi, A. stribrnyi and A. tinctoria) were collected from several regions of the Greek flora and analyzed for their constituent hydroxynaphthoquinones and other metabolites. In most of the above Alkanna samples tested, the main hydroxynaphthoquinones were determined to be β,β-dimethylacrylAlkannin, isovalerylAlkannin + α-methyl-n-butylAlkannin and acetylAlkannin. The hydroxynaphthoquinone constituents and their proportions were found to vary among Alkanna species. Unknown metabolites (not monomeric hydroxynaphthoquinones) were detected by HPLC-PDA-MS, while in several Alkanna species hydroxynaphthoquinones were detected for the first time. Copyright © 2006 John Wiley & Sons, Ltd.
A N Assimopoulou - One of the best experts on this subject based on the ideXlab platform.
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structure radical scavenging activity relationship of Alkannin shikonin derivatives
Food Chemistry, 2011Co-Authors: Stella A. Ordoudi, Stella Tsermentseli, Nikolaos Nenadis, Maria Z. Tsimidou, A N Assimopoulou, Vassilios P PapageorgiouAbstract:Alkannins and shikonins (A/S) are naturally occurring isohexenylnaphthazarins (IHNs) of great interest in the field of life sciences due to their broad spectrum of biological properties and are used as food colourants in some countries. In the present study for the first time assessment of the radical scavenging activity of A/S and selected derivatives was carried out using the Crocin Bleaching Assay (CBA) and a modified DPPH assay. Exploration of structure-radical scavenging activity relationship (SAR) was approached with a wide range of A/S derivatives. To accomplish this task, a computational approach was also employed for the two enantiomers and other structurally related compounds. The findings indicated that the side chain –OH group at C-1′ has a positive effect to the radical scavenging properties of Alkannin/shikonin by assisting hydrogen atom donation from this carbon atom. Thus, Alkannin and shikonin were more potent than deoxyshikonin. Esterification of that hydroxyl group was critical for the activity of the respective compounds (acetyl-, isovaleryl- and β,β-dimethylacryl-shikonin). All of the examined IHN derivatives were found experimentally less potent scavengers than naphthazarin.
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preparative isolation and purification of Alkannin shikonin derivatives from natural products by high speed counter current chromatography
Biomedical Chromatography, 2009Co-Authors: A N Assimopoulou, Hermann Stuppner, Sonja Sturm, Vassilios P PapageorgiouAbstract:Alkannin and shikonin (A/S) and their derivatives have been found in the roots of several Boraginaceous species and are also produced through plant tissue cultures. The chiral compounds A/S are potent pharmaceutical substances with a wide spectrum of biological and pharmacological activities like wound healing, antimicrobial, anti-inflammatory, anticancer and antioxidant activity. High-speed counter-current chromatography (HSCCC) was applied for the first time to the separation, preparative isolation and purification of A/S and their esters from extracts of Alkanna tinctoria roots, as well as commercial samples. The constituents of HSCCC fractions and their purity were determined by high-performance liquid chromatography-diode array detection-mass spectrometry (HPLC-DAD-MS), since DAD cannot detect oligomeric A/S derivatives that are present in most of the samples containing the respective monomeric derivatives. The purity of HSCCC fractions was compared with the one of fractions isolated by column chromatography (CC) using as stationary phases silica gel and Sephadex LH-20. As shown, the purity of monomeric Alkannin/shikonin was greater by HSCCC than CC separation of commercial A/S samples.
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analysis of Alkannin derivatives from alkanna species by high performance liquid chromatography photodiode array mass spectrometry
Biomedical Chromatography, 2006Co-Authors: A N Assimopoulou, Ioannis Karapanagiotis, A. Vasiliou, Stella Kokkini, V. P. PapageorgiouAbstract:Alkannin, shikonin (A/S) and their derivatives are enantiomeric hydroxynaphthoquinone red pigments found in the roots of almost 150 species of the Boraginaceae family. A/S have been shown to exhibit strong wound healing, antimicrobial, anti-inflammatory and antioxidant activities and recent extensive research has well established their antitumor properties. A/S and their derivatives comprise the active ingredients of several pharmaceutical and cosmetic preparations. Although A/S have been efficiently synthesized and have been produced by cell tissue cultures in high yield, most of the pharmaceutical preparations worldwide contain A/S extracted from the roots of Boraginaceous species, found in nature. In the present study, a high-performance liquid chromatography/photodiode array/mass spectrometry (HPLC/PDA/MS) method was established to identify monomeric hydroxynaphthoquinones of the Alkannin series and other metabolites from Boraginaceous root extracts. This method can be applied for the identification of Alkannin derivatives and other metabolites from Boraginaceous cell cultures, and also to determine active ingredients in pharmaceutical preparations containing A/S derivatives. A phytochemical investigation of the Alkanna genus grown in Greece was also performed. Fifty-three root samples belonging to 10 species of the genus Alkanna (A. calliensis, A. corcyrensis, A. graeca, A. methanaea, A. orientalis, A. pindicola, A. primuliflora, A. sieberi, A. stribrnyi and A. tinctoria) were collected from several regions of the Greek flora and analyzed for their constituent hydroxynaphthoquinones and other metabolites. In most of the above Alkanna samples tested, the main hydroxynaphthoquinones were determined to be β,β-dimethylacrylAlkannin, isovalerylAlkannin + α-methyl-n-butylAlkannin and acetylAlkannin. The hydroxynaphthoquinone constituents and their proportions were found to vary among Alkanna species. Unknown metabolites (not monomeric hydroxynaphthoquinones) were detected by HPLC-PDA-MS, while in several Alkanna species hydroxynaphthoquinones were detected for the first time. Copyright © 2006 John Wiley & Sons, Ltd.
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antioxidant activities of Alkannin shikonin and alkanna tinctoria root extracts in oil substrates
Food Chemistry, 2004Co-Authors: A N Assimopoulou, Dimitrioschristos Boskou, V. P. PapageorgiouAbstract:Abstract Alkannin and shikonin (A/S) are potent pharmaceutical substances with a wide spectrum of biological properties and comprise the active ingredients of several pharmaceutical and cosmetic preparations, and are used as food colorants. From a structural point of view, A/S bear both the quinone (naphthoquinone) and the phenolic moiety. Several hydroquinone compounds have been studied for their antioxidant effects, but very little is known about Alkannin and Alkanna tinctoria root extracts that contain several naphthoquinone derivatives (mainly Alkannin esters). The antioxidant activity of A/S and their derivatives, bearing both the quinone and the hydroquinone moiety, was studied in this paper. Several oils and fats were used as oil substrates for the antioxidant assay, namely, lard, corn oil, olive oil and sunflower oil. Dichloromethane extract of A. tinctoria roots, containing mainly Alkannin esters, showed satisfactory antioxidant activity in lard. Shikonin and monomeric Alkannin presented very good antioxidant activity in lard, but their polymerization resulted in partial loss of this activity. The combination of the dichloromethane extract of A. tinctoria roots with caffeic acid showed a synergistic effect. The oxidation of olive oil was retarded when monomeric or polymeric shikonin was present. It can be concluded that A/S and their derivatives, used as active ingredients in pharmaceutical, cosmetic and food preparations, may simultaneously exert antioxidant effects in oil substrates in addition to wound healing, anti-inflammatory and antimicrobial properties. The antioxidant activity of Alkannin is low in corn oil, while monomeric shikonin, combined with citric acid, presents a very moderate antioxidant activity in sunflower oil.
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Alkannin and shikonin effect on free radical processes and on inflammation a preliminary pharmacochemical investigation
Archiv Der Pharmazie, 2002Co-Authors: Angeliki P Kourounakis, Vassilios P Papageorgiou, A N Assimopoulou, Antonis Gavalas, Panos N KourounakisAbstract:Alkannin and shikonin, two natural products from Alkanna tinctoria and Lithospermum erhythrorhizon (Boraginaceae), are used in folk medicine where they are claimed to possess, among other properties, wound healing and anti-inflammatory activity. We investigated, together with the structurally related naphthazarin, their in vitro antioxidant and hydroxyl radical scavenging activity as well as their in vivo antiinflammatory activity. I was found that all examined compounds significantly inhibited in vitro lipid peroxidation of ra hepatic microsomal membranes, competed with DMSO for free hydroxyl radicals, and reduced inflammation (mouse paw edema induced by FCA) very efficiently. The examined compounds proved equal or superior to the common reference compounds for each of these properties. I is concluded that the claimed and/or proven actions of Alkannin and shikonin are attributable at least partly to their intervention in free radical processes.
V. P. Papageorgiou - One of the best experts on this subject based on the ideXlab platform.
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Simultaneous determination of monomeric and oligomeric Alkannins and shikonins by high-performance liquid chromatography-diode array detection-mass spectrometry.
Biomedical chromatography : BMC, 2008Co-Authors: Andreana N Assimopoulou, Markus Ganzera, Hermann Stuppner, V. P. PapageorgiouAbstract:Alkannin and shikonin (A/S) derivatives have been found in the roots of several Boraginaceous species and are produced through plant tissue cultures. The chiral compounds Alkannins and shikonins are potent pharmaceutical substances with a wide spectrum of pharmacological activities such as wound healing, antimicrobial, anti-inflammatory, anticancer and antioxidant. Although oligomeric A/S derivatives have been detected in root extracts and commercial samples their detection and determination through high-performance liquid chromatography has not been reported. Therefore, in the present study a rapid, simple high-performance liquid chromatography–diode array detection–mass spectrometry (HPLC-DAD-MS) method was developed to detect, separate and determine monomeric and oligomeric/polymeric derivatives of Alkannin/shikonin simultaneously for the first time. An optimization of HPLC-DAD parameters was performed. Both atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) modes were applied, in order to compare detection of monomeric and oligomeric A/S. Additionally, oligomeric A/S constituents in several samples were identified and the mode of A/S polymerization was proposed. Copyright © 2007 John Wiley & Sons, Ltd.
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analysis of Alkannin derivatives from alkanna species by high performance liquid chromatography photodiode array mass spectrometry
Biomedical Chromatography, 2006Co-Authors: A N Assimopoulou, Ioannis Karapanagiotis, A. Vasiliou, Stella Kokkini, V. P. PapageorgiouAbstract:Alkannin, shikonin (A/S) and their derivatives are enantiomeric hydroxynaphthoquinone red pigments found in the roots of almost 150 species of the Boraginaceae family. A/S have been shown to exhibit strong wound healing, antimicrobial, anti-inflammatory and antioxidant activities and recent extensive research has well established their antitumor properties. A/S and their derivatives comprise the active ingredients of several pharmaceutical and cosmetic preparations. Although A/S have been efficiently synthesized and have been produced by cell tissue cultures in high yield, most of the pharmaceutical preparations worldwide contain A/S extracted from the roots of Boraginaceous species, found in nature. In the present study, a high-performance liquid chromatography/photodiode array/mass spectrometry (HPLC/PDA/MS) method was established to identify monomeric hydroxynaphthoquinones of the Alkannin series and other metabolites from Boraginaceous root extracts. This method can be applied for the identification of Alkannin derivatives and other metabolites from Boraginaceous cell cultures, and also to determine active ingredients in pharmaceutical preparations containing A/S derivatives. A phytochemical investigation of the Alkanna genus grown in Greece was also performed. Fifty-three root samples belonging to 10 species of the genus Alkanna (A. calliensis, A. corcyrensis, A. graeca, A. methanaea, A. orientalis, A. pindicola, A. primuliflora, A. sieberi, A. stribrnyi and A. tinctoria) were collected from several regions of the Greek flora and analyzed for their constituent hydroxynaphthoquinones and other metabolites. In most of the above Alkanna samples tested, the main hydroxynaphthoquinones were determined to be β,β-dimethylacrylAlkannin, isovalerylAlkannin + α-methyl-n-butylAlkannin and acetylAlkannin. The hydroxynaphthoquinone constituents and their proportions were found to vary among Alkanna species. Unknown metabolites (not monomeric hydroxynaphthoquinones) were detected by HPLC-PDA-MS, while in several Alkanna species hydroxynaphthoquinones were detected for the first time. Copyright © 2006 John Wiley & Sons, Ltd.
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Analysis of Alkannin derivatives from Alkanna species by high-performance liquid chromatography/photodiode array/mass spectrometry.
Biomedical chromatography : BMC, 2006Co-Authors: Andreana N Assimopoulou, Ioannis Karapanagiotis, A. Vasiliou, Stella Kokkini, V. P. PapageorgiouAbstract:Alkannin, shikonin (A/S) and their derivatives are enantiomeric hydroxynaphthoquinone red pigments found in the roots of almost 150 species of the Boraginaceae family. A/S have been shown to exhibit strong wound healing, antimicrobial, anti-inflammatory and antioxidant activities and recent extensive research has well established their antitumor properties. A/S and their derivatives comprise the active ingredients of several pharmaceutical and cosmetic preparations. Although A/S have been efficiently synthesized and have been produced by cell tissue cultures in high yield, most of the pharmaceutical preparations worldwide contain A/S extracted from the roots of Boraginaceous species, found in nature. In the present study, a high-performance liquid chromatography/photodiode array/mass spectrometry (HPLC/PDA/MS) method was established to identify monomeric hydroxynaphthoquinones of the Alkannin series and other metabolites from Boraginaceous root extracts. This method can be applied for the identification of Alkannin derivatives and other metabolites from Boraginaceous cell cultures, and also to determine active ingredients in pharmaceutical preparations containing A/S derivatives. A phytochemical investigation of the Alkanna genus grown in Greece was also performed. Fifty-three root samples belonging to 10 species of the genus Alkanna (A. calliensis, A. corcyrensis, A. graeca, A. methanaea, A. orientalis, A. pindicola, A. primuliflora, A. sieberi, A. stribrnyi and A. tinctoria) were collected from several regions of the Greek flora and analyzed for their constituent hydroxynaphthoquinones and other metabolites. In most of the above Alkanna samples tested, the main hydroxynaphthoquinones were determined to be β,β-dimethylacrylAlkannin, isovalerylAlkannin + α-methyl-n-butylAlkannin and acetylAlkannin. The hydroxynaphthoquinone constituents and their proportions were found to vary among Alkanna species. Unknown metabolites (not monomeric hydroxynaphthoquinones) were detected by HPLC-PDA-MS, while in several Alkanna species hydroxynaphthoquinones were detected for the first time. Copyright © 2006 John Wiley & Sons, Ltd.
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Radical scavenging activity of Alkanna tinctoria root extracts and their main constituents, hydroxynaphthoquinones
Phytotherapy research : PTR, 2005Co-Authors: Andreana N Assimopoulou, V. P. PapageorgiouAbstract:Alkannin and shikonin (A[sol ]S) are pharmaceutical substances with a wide spectrum of biological properties. Radical scavenging activity is involved in aging processes, antiinsammatory, anticancer and wound healing activities. Hence, in the present study the DPPH radical scavenging activity of Alkannin and shikonin, both monomeric and oligomeric, and extracts of Alkanna tinctoria roots were studied and a structure–activity relationship was approximated. It was shown that both monomeric and oligomeric Alkannin and shikonin and also A[sol ]S esters exhibited extremely high radical scavenging activity. The presence of the naphthoquinone moiety seems to be essential for that activity, while the side chain of A[sol ]S possibly plays a minor role. Esterification of A[sol ]S on the side chain hydroxyl group does not affect radical scavenging activity. Organic solvents and olive oil (extracted at room temperature) extracts of Alkanna tinctoria roots, which contain as active ingredients A[sol ]S esters, exhibited very good antiradical activity. Alkannin and shikonin and their esters and also extracts of Alkanna tinctoria roots could be used promisingly in pharmaceutical and cosmetic preparations for their radical scavenging activity and probably for their antiaging activity. Copyright © 2005 John Wiley & Sons, Ltd.
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antioxidant activities of Alkannin shikonin and alkanna tinctoria root extracts in oil substrates
Food Chemistry, 2004Co-Authors: A N Assimopoulou, Dimitrioschristos Boskou, V. P. PapageorgiouAbstract:Abstract Alkannin and shikonin (A/S) are potent pharmaceutical substances with a wide spectrum of biological properties and comprise the active ingredients of several pharmaceutical and cosmetic preparations, and are used as food colorants. From a structural point of view, A/S bear both the quinone (naphthoquinone) and the phenolic moiety. Several hydroquinone compounds have been studied for their antioxidant effects, but very little is known about Alkannin and Alkanna tinctoria root extracts that contain several naphthoquinone derivatives (mainly Alkannin esters). The antioxidant activity of A/S and their derivatives, bearing both the quinone and the hydroquinone moiety, was studied in this paper. Several oils and fats were used as oil substrates for the antioxidant assay, namely, lard, corn oil, olive oil and sunflower oil. Dichloromethane extract of A. tinctoria roots, containing mainly Alkannin esters, showed satisfactory antioxidant activity in lard. Shikonin and monomeric Alkannin presented very good antioxidant activity in lard, but their polymerization resulted in partial loss of this activity. The combination of the dichloromethane extract of A. tinctoria roots with caffeic acid showed a synergistic effect. The oxidation of olive oil was retarded when monomeric or polymeric shikonin was present. It can be concluded that A/S and their derivatives, used as active ingredients in pharmaceutical, cosmetic and food preparations, may simultaneously exert antioxidant effects in oil substrates in addition to wound healing, anti-inflammatory and antimicrobial properties. The antioxidant activity of Alkannin is low in corn oil, while monomeric shikonin, combined with citric acid, presents a very moderate antioxidant activity in sunflower oil.
Yujun Zheng - One of the best experts on this subject based on the ideXlab platform.
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Theoretical Insights Into the Excited State Double Proton Transfer Mechanism of Deep Red Pigment Alkannin.
The journal of physical chemistry. A, 2018Co-Authors: Jinfeng Zhao, Hao Dong, Yujun ZhengAbstract:As the most important component of deep red pigments, Alkannin is investigated theoretically in detail based on time-dependent density functional theory (TDDFT) method. Exploring the dual intramolecular hydrogen bonds (O1–H2···O3 and O4–H5···O6) of Alkannin, we confirm the O1–H2···O3 may play a more important role in the first excited state than the O4–H5···O6 one. Infrared (IR) vibrational analyses and subsequent charge redistribution also support this viewpoint. Via constructing the S1-state potential energy surface (PES) and searching transition state (TS) structures, we illuminate the excited state double proton transfer (ESDPT) mechanism of Alkannin is the stepwise process that can be first launched by the O1–H2···O3 hydrogen bond wire in gas state, acetonitrile (CH3CN) and cyclohexane (CYH) solvents. We present a novel mechanism that polar aprotic solvents can contribute to the first-step proton transfer (PT) process in the S1 state, and nonpolar solvents play important roles in lowering the potenti...
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Theoretical Insights Into the Excited State Double Proton Transfer Mechanism of Deep Red Pigment Alkannin
2018Co-Authors: Jinfeng Zhao, Hao Dong, Yujun ZhengAbstract:As the most important component of deep red pigments, Alkannin is investigated theoretically in detail based on time-dependent density functional theory (TDDFT) method. Exploring the dual intramolecular hydrogen bonds (O1–H2···O3 and O4–H5···O6) of Alkannin, we confirm the O1–H2···O3 may play a more important role in the first excited state than the O4–H5···O6 one. Infrared (IR) vibrational analyses and subsequent charge redistribution also support this viewpoint. Via constructing the S1-state potential energy surface (PES) and searching transition state (TS) structures, we illuminate the excited state double proton transfer (ESDPT) mechanism of Alkannin is the stepwise process that can be first launched by the O1–H2···O3 hydrogen bond wire in gas state, acetonitrile (CH3CN) and cyclohexane (CYH) solvents. We present a novel mechanism that polar aprotic solvents can contribute to the first-step proton transfer (PT) process in the S1 state, and nonpolar solvents play important roles in lowering the potential energy barrier of the second-step PT reaction
