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Vassilios P Papageorgiou – One of the best experts on this subject based on the ideXlab platform.

  • Electrospun fiber mats containing shikonin and derivatives with potential biomedical applications.
    International journal of pharmaceutics, 2011
    Co-Authors: Konstantinos N Kontogiannopoulos, Andreana N Assimopoulou, Ioannis Tsivintzelis, Costas Panayiotou, Vassilios P Papageorgiou
    Abstract:

    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.

  • Structure-radical scavenging activity relationship of Alkannin/shikonin derivatives
    Food Chemistry, 2011
    Co-Authors: Stella A. Ordoudi, Andreana N Assimopoulou, Stella Tsermentseli, Nikolaos Nenadis, Maria Z. Tsimidou, Vassilios P Papageorgiou
    Abstract:

    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.

  • structure radical scavenging activity relationship of Alkannin shikonin derivatives
    Food Chemistry, 2011
    Co-Authors: Stella A. Ordoudi, Stella Tsermentseli, Nikolaos Nenadis, Maria Z. Tsimidou, A N Assimopoulou, Vassilios P Papageorgiou
    Abstract:

    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.

Andreana N Assimopoulou – One of the best experts on this subject based on the ideXlab platform.

  • Electrospun fiber mats containing shikonin and derivatives with potential biomedical applications.
    International journal of pharmaceutics, 2011
    Co-Authors: Konstantinos N Kontogiannopoulos, Andreana N Assimopoulou, Ioannis Tsivintzelis, Costas Panayiotou, Vassilios P Papageorgiou
    Abstract:

    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.

  • Structure-radical scavenging activity relationship of Alkannin/shikonin derivatives
    Food Chemistry, 2011
    Co-Authors: Stella A. Ordoudi, Andreana N Assimopoulou, Stella Tsermentseli, Nikolaos Nenadis, Maria Z. Tsimidou, Vassilios P Papageorgiou
    Abstract:

    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.

  • Preparative isolation and purification of Alkannin/shikonin derivatives from natural products by high-speed counter-current chromatography.
    Biomedical chromatography : BMC, 2009
    Co-Authors: Andreana N Assimopoulou, Hermann Stuppner, Sonja Sturm, Vassilios P Papageorgiou
    Abstract:

    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 puripurification 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 chrochromatographydiode 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 chrochromatography (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.

A N Assimopoulou – One of the best experts on this subject based on the ideXlab platform.

  • structure radical scavenging activity relationship of Alkannin shikonin derivatives
    Food Chemistry, 2011
    Co-Authors: Stella A. Ordoudi, Stella Tsermentseli, Nikolaos Nenadis, Maria Z. Tsimidou, A N Assimopoulou, Vassilios P Papageorgiou
    Abstract:

    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.

  • preparative isolation and purification of Alkannin shikonin derivatives from natural products by high speed counter current chromatography
    Biomedical Chromatography, 2009
    Co-Authors: A N Assimopoulou, Hermann Stuppner, Sonja Sturm, Vassilios P Papageorgiou
    Abstract:

    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 puripurification 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 chrochromatographydiode 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 chrochromatography (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.

  • analysis of Alkannin derivatives from alkanna species by high performance liquid chromatography photodiode array mass spectrometry
    Biomedical Chromatography, 2006
    Co-Authors: A N Assimopoulou, Ioannis Karapanagiotis, A. Vasiliou, Stella Kokkini, V. P. Papageorgiou
    Abstract:

    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 chrochromatography/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.

V. P. Papageorgiou – One of the best experts on this subject based on the ideXlab platform.

  • Simultaneous determination of monomeric and oligomeric Alkannins and shikonins by high-performance liquid chromatography-diode array detection-mass spectrometry.
    Biomedical chromatography : BMC, 2008
    Co-Authors: Andreana N Assimopoulou, Hermann Stuppner, Markus Ganzera, V. P. Papageorgiou
    Abstract:

    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 chrochromatography has not been reported. Therefore, in the present study a rapid, simple high-performance liquid chrochromatographydiode 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 ioniionization (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.

  • analysis of Alkannin derivatives from alkanna species by high performance liquid chromatography photodiode array mass spectrometry
    Biomedical Chromatography, 2006
    Co-Authors: A N Assimopoulou, Ioannis Karapanagiotis, A. Vasiliou, Stella Kokkini, V. P. Papageorgiou
    Abstract:

    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.

  • Analysis of Alkannin derivatives from Alkanna species by high-performance liquid chromatography/photodiode array/mass spectrometry.
    Biomedical chromatography : BMC, 2006
    Co-Authors: Andreana N Assimopoulou, Ioannis Karapanagiotis, A. Vasiliou, Stella Kokkini, V. P. Papageorgiou
    Abstract:

    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 chrochromatography/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.

Yujun Zheng – One of the best experts on this subject based on the ideXlab platform.

  • Theoretical Insights Into the Excited State Double Proton Transfer Mechanism of Deep Red Pigment Alkannin.
    The journal of physical chemistry. A, 2018
    Co-Authors: Jinfeng Zhao, Hao Dong, Yujun Zheng
    Abstract:

    As the most important component of deep red pigments, Alkannin is investigated theoretically in detail based on time-dependent density funcfunctional 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…

  • Theoretical Insights Into the Excited State Double Proton Transfer Mechanism of Deep Red Pigment Alkannin
    , 2018
    Co-Authors: Jinfeng Zhao, Hao Dong, Yujun Zheng
    Abstract:

    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 enerenergy barrier of the second-step PT reaction