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Gunasekera, Sunithi
Publications (10 of 31) Show all publications
Mohotti, S., Rajendran, S., Muhammad, T., Strömstedt, A. A., Adhikari, A., Burman, R., . . . Gunasekera, S. (2019). Screening for bioactive secondary metabolites in Sri Lankan medicinal plants by microfractionation and targeted isolation of antimicrobial flavonoids from Derris scandens. Journal of Ethnopharmacology, 246, Article ID 112158.
Open this publication in new window or tab >>Screening for bioactive secondary metabolites in Sri Lankan medicinal plants by microfractionation and targeted isolation of antimicrobial flavonoids from Derris scandens
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2019 (English)In: Journal of Ethnopharmacology, ISSN 0378-8741, E-ISSN 1872-7573, Vol. 246, article id 112158Article in journal (Refereed) Published
Abstract [en]

Ethnopharmacological relevance: Sri Lanka is known to have very diverse flora. Many of these species are used for plant-based remedies, which form the integral part of two Sri Lankan systems of traditional medicine, Ayurveda and Deshiya Chikitsa. Despite their widespread use, only a limited number of studies have probed into the scientific evidence for bioactivity of these medicinal plants. Such studies rarely progress to the identification of bioactive natural products. Aim of the study: The primary aim was to develop a bioactivity screening method and apply it to 50 Sri Lankan medicinal plants where antimicrobial properties could be relevant for its traditional use. The subsequent aim was the progression into defining and characterising potent isolates within targeted compound classes from such plants, i.e. Derris scandens and its antimicrobial flavonoids. Material and methods: The plant collection comprised 24 species of Fabaceae, 15 Rubiaceae, 7 Solanaceae and 4 Cucurbitaceae plants. These 50 species were collected based on their ethnopharmacological importance and use in Sri Lankan traditional medicine. Crude extracts from each species were initially subjected to radial disc diffusion and microdilution assays. Subsequently, aqueous extracts of all plants were microfractionated in deep well plates using reversed-phase HPLC. Fractions were tested for antibacterial and cytotoxic activities and masses of target bioactive compounds were identified using mass spectrometry. Bioactive compounds with the masses identified through microfractions were isolated from Derris scandens using reversed-phase HPLC. The isolated pure compounds were characterised using LC-MS and NMR. Results: Crude aqueous extracts from 19 species showed activity against Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus) in the radial disc diffusion assay. Crude aqueous extracts from 34 plant species and organic extracts from 46 plant species were active against S. aureus (<= 4 mg mL(-1)) in the microdilution assay. Microfractionation demonstrated antibacterial activity for 19 plants and cytotoxicity for 6 plants. Furthermore, target bioactive compounds and their molecular ions were identified during microfractionation. Dalpanitin and vicenin-3, two of the flavonoids isolated from Derris scandens gave MICs of 23 mu g mL(-1) against S. aureus. Dalpanitin also exhibited relevant MICs on Gram-negative bacteria (94 mu g mL(-1)) against Escherichia coli and Pseudomonas aeruginosa). Conclusion: The microfractionation protocol developed in this study enabled time-efficient screening of many plants species, using a small quantity of sample material. In addition, microfractionation served as a guiding tool for identifying individual antimicrobial compounds. Through this process, flavonoids were isolated from Derris scandens, out of which dalpanitin and vicenin-3 showed activity in the low micromolar range. The high hit rate for in vitro antibacterial properties from this ethnopharmacologically guided sample collection gives credence to Sri Lankan traditional herbal medicine as a source for drug discovery.

Keywords
Sri Lanka, Medicinal plants, Microfractionation, Antimicrobial activity, Cytotoxicity, Flavonoids
National Category
Pharmacology and Toxicology
Identifiers
urn:nbn:se:uu:diva-397136 (URN)10.1016/j.jep.2019.112158 (DOI)000493211800010 ()31421182 (PubMedID)
Funder
Swedish Research Council, 2013-06672
Available from: 2019-11-28 Created: 2019-11-28 Last updated: 2019-11-28Bibliographically approved
Gunasekera, S., Muhammad, T., Strömstedt, A. A., Rosengren, K. J. & Göransson, U. (2018). Alanine and Lysine Scans of the LL-37-Derived Peptide Fragment KR-12 Reveal Key Residues for Antimicrobial Activity. ChemBioChem (Print), 19(9), 931-939
Open this publication in new window or tab >>Alanine and Lysine Scans of the LL-37-Derived Peptide Fragment KR-12 Reveal Key Residues for Antimicrobial Activity
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2018 (English)In: ChemBioChem (Print), ISSN 1439-4227, E-ISSN 1439-7633, Vol. 19, no 9, p. 931-939Article in journal (Refereed) Published
Abstract [en]

The human host defence peptide LL-37 is a broad-spectrum antibiotic with immunomodulatory functions. Residues 18-29 in LL-37 have previously been identified as a minimal peptide (KR-12) that retains antibacterial activity with decreased cytotoxicity. In this study, analogues of KR-12 were generated by Ala and Lys scans to identify key elements for activity. These were tested against a panel of human pathogens and for membrane permeabilisation on liposomes. Replacements of hydrophobic and cationic residues with Ala were detrimental for antibiotic potency. Substitutions by Lys increased activity, as long as the increase in cationic density did not disrupt the amphiphilic disposition of the helical structure. Importantly, substitutions showed differential effects against different organisms. Replacement of Gln5 with Lys and Asp9 with Ala or Lys improved the broad-spectrum activity most, each resulting in up to an eightfold increase in potency against Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans. The improved analogues displayed no significant toxicity against human cells, and thus, KR-12 is a tuneable template for antibiotic development.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2018
Keywords
antibiotics, cytotoxicity, drug discovery, peptides, structure-activity relationships
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:uu:diva-356391 (URN)10.1002/cbic.201700599 (DOI)000431625100008 ()29430821 (PubMedID)
Funder
Swedish Research Council, 2011-3403Carl Tryggers foundation , CTS 10: 126Carl Tryggers foundation , CTS 11: 169Swedish Society of Medicine, SLS-254511
Available from: 2018-07-25 Created: 2018-07-25 Last updated: 2020-02-18Bibliographically approved
Zumberge, J. A., Love, G. D., Cárdenas, P., Sperling, E. A., Gunasekera, S., Rohrssen, M., . . . Summons, R. E. (2018). Demosponge steroid biomarker 26-methylstigmastane provides evidence for Neoproterozoic animals. Nature Ecology & Evolution, 2(11), 1709-1714
Open this publication in new window or tab >>Demosponge steroid biomarker 26-methylstigmastane provides evidence for Neoproterozoic animals
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2018 (English)In: Nature Ecology & Evolution, E-ISSN 2397-334X, Vol. 2, no 11, p. 1709-1714Article in journal (Refereed) Published
Abstract [en]

Sterane biomarkers preserved in ancient sedimentary rocks hold promise for tracking the diversification and ecological expansion of eukaryotes. The earliest proposed animal biomarkers from demosponges (Demospongiae) are recorded in a sequence around 100 Myr long of Neoproterozoic-Cambrian marine sedimentary strata from the Huqf Supergroup, South Oman Salt Basin. This C-30 sterane biomarker, informally known as 24-isopropylcholestane (24-ipc), possesses the same carbon skeleton as sterols found in some modern-day demosponges. However, this evidence is controversial because 24-ipc is not exclusive to demosponges since 24-ipc sterols are found in trace amounts in some pelagophyte algae. Here, we report a new fossil sterane biomarker that co-occurs with 24-ipc in a suite of late Neoproterozoic-Cambrian sedimentary rocks and oils, which possesses a rare hydrocarbon skeleton that is uniquely found within extant demosponge taxa. This sterane is informally designated as 26-methylstigmastane (26-mes), reflecting the very unusual methylation at the terminus of the steroid side chain. It is the first animal-specific sterane marker detected in the geological record that can be unambiguously linked to precursor sterols only reported from extant demosponges. These new findings strongly suggest that demosponges, and hence multicellular animals, were prominent in some late Neoproterozoic marine environments at least extending back to the Cryogenian period.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2018
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-370005 (URN)10.1038/s41559-018-0676-2 (DOI)000447964800013 ()30323207 (PubMedID)
Funder
EU, Horizon 2020, 679849
Available from: 2019-01-07 Created: 2019-01-07 Last updated: 2019-01-07Bibliographically approved
Wang, Y., Lloyd, K. A., Gunasekera, S., Eriksson, C., Ramsköld, D., Lundberg, K., . . . Grönwall, C. (2018). Repertoire Studies in Rheumatoid Arthritis Reveal B-Cell Distortions and Baseline Shifts in Unmutated IgG. Arthritis & Rheumatology, 70
Open this publication in new window or tab >>Repertoire Studies in Rheumatoid Arthritis Reveal B-Cell Distortions and Baseline Shifts in Unmutated IgG
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2018 (English)In: Arthritis & Rheumatology, ISSN 2326-5191, E-ISSN 2326-5205, Vol. 70Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
John Wiley & Sons, 2018
National Category
Rheumatology and Autoimmunity
Identifiers
urn:nbn:se:uu:diva-369631 (URN)000447268900009 ()
Available from: 2018-12-17 Created: 2018-12-17 Last updated: 2018-12-17Bibliographically approved
Gunasekera, S., Fernandes-Cerqueira, C., Wennmalm, S., Wahamaa, H., Sommarin, Y., Catrina, A. I., . . . Göransson, U. (2018). Stabilized Cyclic Peptides as Scavengers of Autoantibodies: Neutralization of Anticitrullinated Protein/Peptide Antibodies in Rheumatoid Arthritis. ACS Chemical Biology, 13(6), 1525-1535
Open this publication in new window or tab >>Stabilized Cyclic Peptides as Scavengers of Autoantibodies: Neutralization of Anticitrullinated Protein/Peptide Antibodies in Rheumatoid Arthritis
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2018 (English)In: ACS Chemical Biology, ISSN 1554-8929, E-ISSN 1554-8937, Vol. 13, no 6, p. 1525-1535Article in journal (Refereed) Published
Abstract [en]

The occurrence of autoantibodies is a hallmark of rheumatoid arthritis, specifically those autoantibodies targeting proteins containing the arginine-derived amino acid citrulline. There is strong evidence showing that the occurrence of anticitrullinated protein/peptide antibodies (ACPA) are involved in disease progression, and ACPA was recently shown to induce pain in animals. Here, we explore a novel concept useful for research, diagnostics, and possibly therapy of autoimmune diseases, namely, to directly target and neutralize autoantibodies using peptide binders. A high-affinity peptide-based scavenger of ACPA was developed by grafting a citrullinated epitope derived from human fibrinogen into a naturally occurring stable peptide scaffold. The best scavenger comprises the truncated epitope alpha-fibrinogen, [Cit573]fib(566-580), grafted into the scaffold sunflower trypsin inhibitor-1, SFTI-1. The final peptide demonstrates low nanomolar apparent affinity and superior stability.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
National Category
Rheumatology and Autoimmunity
Identifiers
urn:nbn:se:uu:diva-358527 (URN)10.1021/acschembio.8b00118 (DOI)000435746200015 ()29630823 (PubMedID)
Funder
Swedish Research Council, 2012-5063Swedish Research Council, 2017-02577Swedish Foundation for Strategic Research , F06-0058Swedish Rheumatism Association, R-755861Stockholm County Council, 20160378
Available from: 2018-09-03 Created: 2018-09-03 Last updated: 2018-09-03Bibliographically approved
Hellinger, R., Thell, K., Vasileva, M., Muhammad, T., Gunasekera, S., Kuemmel, D., . . . Gruber, C. W. (2017). Chemical Proteomics for Target Discovery of Head-to-Tail Cyclized Mini-Proteins. Frontiers in Chemistry, 5, Article ID 73.
Open this publication in new window or tab >>Chemical Proteomics for Target Discovery of Head-to-Tail Cyclized Mini-Proteins
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2017 (English)In: Frontiers in Chemistry, E-ISSN 2296-2646, Vol. 5, article id 73Article in journal (Refereed) Published
Abstract [en]

Target deconvolution is one of the most challenging tasks in drug discovery, but a key step in drug development. In contrast to small molecules, there is a lack of validated and robust methodologies for target elucidation of peptides. In particular, it is difficult to apply these methods to cyclic and cysteine-stabilized peptides since they exhibit reduced amenability to chemical modification and affinity capture; however, such ribosomally synthesized and post-translationally modified peptide natural products are rich sources of promising drug candidates. For example, plant-derived circular peptides called cyclotides have recently attracted much attention due to their immunosuppressive effects and oral activity in the treatment of multiple sclerosis in mice, but their molecular target has hitherto not been reported. In this study, a chemical proteomics approach using photo-affinity crosslinking was developed to determine a target for the circular peptide [T20K]kalata B1. Using this prototypic nature-derived peptide enabled the identification of a possible functional modulation of 14-3-3 proteins. This biochemical interaction was validated via competition pull down assays as well as a cellular reporter assay indicating an effect on 14-3-3-dependent transcriptional activity. As proof of concept, the presented approach may be applicable for target elucidation of various cyclic peptides and mini-proteins, in particular cyclotides, which represent a promising class of molecules in drug discovery and development.

Place, publisher, year, edition, pages
FRONTIERS MEDIA SA, 2017
Keywords
cyclotides, cyclic protein, chemical proteomics, peptide-protein interaction, photo-affinity labeling
National Category
Pharmaceutical Sciences
Identifiers
urn:nbn:se:uu:diva-338516 (URN)10.3389/fchem.2017.00073 (DOI)000412726000001 ()29075625 (PubMedID)
Funder
Australian Research Council, FT140100730
Available from: 2018-01-15 Created: 2018-01-15 Last updated: 2018-01-15Bibliographically approved
Mohotti, S., Rajendran, S., Muhammad, T., Strömstedt, A. A., Burman, R., Hellman, B., . . . Gunasekera, S. (2016). A bioactivity-guided screening of Sri Lankan plants in the search for novel antibacterial and anticancer agents. Paper presented at 9th Joint Meeting of AFERP, ASP, GA, JSP, PSE and SIF, JUL 24-27, 2016, Copenhagen, DENMARK. Planta Medica, 82
Open this publication in new window or tab >>A bioactivity-guided screening of Sri Lankan plants in the search for novel antibacterial and anticancer agents
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2016 (English)In: Planta Medica, ISSN 0032-0943, E-ISSN 1439-0221, Vol. 82Article in journal, Meeting abstract (Other academic) Published
Keywords
Ayurvedic, MIC, NMR, FMCA, antibacterial, anticancer
National Category
Pharmacology and Toxicology
Identifiers
urn:nbn:se:uu:diva-346857 (URN)10.1055/s-0036-1596561 (DOI)000411789300385 ()
Conference
9th Joint Meeting of AFERP, ASP, GA, JSP, PSE and SIF, JUL 24-27, 2016, Copenhagen, DENMARK
Available from: 2018-03-27 Created: 2018-03-27 Last updated: 2018-03-27Bibliographically approved
Gunasekera, S., Fernandes-Cerqueira, C., Eriksson, C., Jakobsson, P.-J. & Göransson, U. (2016). Anti-Citrullinated Peptide Antibody Inhibitors Based On Sunflower Trypsin Inhibitor-1 Scaffold For Potential Anti-Rheumatoid Arthritis Activity. Journal of Peptide Science, 22(S2), S170-S170
Open this publication in new window or tab >>Anti-Citrullinated Peptide Antibody Inhibitors Based On Sunflower Trypsin Inhibitor-1 Scaffold For Potential Anti-Rheumatoid Arthritis Activity
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2016 (English)In: Journal of Peptide Science, ISSN 1075-2617, E-ISSN 1099-1387, Vol. 22, no S2, p. S170-S170Article in journal, Meeting abstract (Other academic) Published
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:uu:diva-331382 (URN)10.1002/psc.2950 (DOI)000398216100317 ()
Available from: 2017-10-17 Created: 2017-10-17 Last updated: 2017-10-17Bibliographically approved
Gunasekera, S., Fernandes-Cerqueira, C., Eriksson, C., Jakobsson, P. J. & Göransson, U. (2016). Circular disulfide-rich peptide scaffolds as anti-citrullinated peptide antibody inhibitors. Paper presented at 9th Joint Meeting of AFERP, ASP, GA, JSP, PSE and SIF, JUL 24-27, 2016, Copenhagen, DENMARK. Planta Medica, 82
Open this publication in new window or tab >>Circular disulfide-rich peptide scaffolds as anti-citrullinated peptide antibody inhibitors
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2016 (English)In: Planta Medica, ISSN 0032-0943, E-ISSN 1439-0221, Vol. 82Article in journal, Meeting abstract (Other academic) Published
Keywords
anti-citrullinated protein/peptide antibodies (ACPA), cyclic peptide, fibrinogen, NMR, target, sunflower trypsin inhibitor 1 (SFTI-1)
National Category
Pharmacology and Toxicology
Identifiers
urn:nbn:se:uu:diva-346853 (URN)10.1055/s-0036-1596779 (DOI)000411789300603 ()
Conference
9th Joint Meeting of AFERP, ASP, GA, JSP, PSE and SIF, JUL 24-27, 2016, Copenhagen, DENMARK
Available from: 2018-03-27 Created: 2018-03-27 Last updated: 2018-03-27Bibliographically approved
Muhammad, T., Gunasekera, S., Strömstedt, A. A. & Göransson, U. (2016). Engineering Of A Minimalized Domain Derived From Human Host Defense Peptide LL-37 Into A Stable And Potent Antimicrobial Drug Lead. Journal of Peptide Science, 22(S2), S184-S186
Open this publication in new window or tab >>Engineering Of A Minimalized Domain Derived From Human Host Defense Peptide LL-37 Into A Stable And Potent Antimicrobial Drug Lead
2016 (English)In: Journal of Peptide Science, ISSN 1075-2617, E-ISSN 1099-1387, Vol. 22, no S2, p. S184-S186Article in journal, Meeting abstract (Other academic) Published
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:uu:diva-331384 (URN)10.1002/psc.2950 (DOI)000398216100347 ()
Available from: 2017-10-17 Created: 2017-10-17 Last updated: 2017-10-17Bibliographically approved
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