Graduate Studies

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Author: search.filters.author.Paranagama, P.A.Subject: search.filters.subject.endolichenic fungi

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    Secondary Metabolites with Radical Scavenging Activity from Daldinia Eschcholzii, Isolated from The Lichen Parmotrema Sp. In Sri Lanka-Isolation and Structure Determination
    (Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Manthrirathna, M.A.T.P.; Kandiah, R.; Gunasekara, D.S.; Paranagama, P.A.
    Natural products are promising leads for novel therapeutic agents. Isolation and characterization of bioactive compounds in search for potential pharmocophores has acquired a developing interest in on-going research. Although Endolichenic fungi (EF) are a rich source of bioactive secondary metabolites, they still remain almost unexploited. The present study is focused on isolation and structure elucidation of compounds with radical scavenging activity from the EF, Daldinia eschscholzii that occur in the lichen Parmotrema sp. in Hakgala Botanical Garden, Sri Lanka. Daldinia eschscholzii cultivated on 48 large petri dishes with PDA were incubated at room temperature for one week. Mycelia were cut in to small pieces along with the medium and extracted with ethyl acetate twice. The radical scavenging activity of the crude extract was evaluated using DPPH assay. Standard antioxidant, Butylated Hydroxy Toluene (BHT) and MeOH were used as the positive control (IC50= 38.2 ± 4.0 μg/ mL) and negative control respectively. The crude extract with high radical scavenging activity (IC50 = 77.9 ± 5.1 μg/ mL), was partitioned with hexane, chloroform and aqueous methanol. All three organic extracts were then subjected to DPPH assay. Chloroform fraction with the highest activity (IC50= 63.8 ± 4.8 μg/ mL) was further fractionated using silica gel, sephadex column chromatography and preparative TLC to isolate two pure compounds. The structures of the compounds were elucidated using 1H, 13C, 2D NMR and MS data. The compounds were identified as 7-hydroxy- 2-methylchroman-4-one (1) and 5-methoxynaphthalen-1-ol (2). Compound 1 showed no activity in the assay. Compound 2 showed higher activity than the standard BHT, with IC50 value of 10.2 ± 5.8 μg/ mL.
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    New Bioactive poliketide from endolichenic fungus, Curvularia trifolii, inhabiting the lichen, Usnea sp. collected from Haggala Botanical Garden
    (Faculty of Graduate Studies, University of Kelaniya, 2015) Samanthi, K.A.U.; Wickramaarachchi, S.; Wijerathne, E.M.K.; Paranagama, P.A.
    Endolichenic fungi (ELF), which live in healthy tissues of lichens, are one of the promising producers of structurally diverse novel bioactive secondary metabolites. It has been reported that endolichenic fungi are rich sources for the discovery of new compounds with significant medicinal values and this was demonstrated by isolation and identification of new anticancer, antifungal, antibacterial and antioxidant agents from endolichenic fungal extracts. In Sri Lanka, research group of University of Kelaniya initiated a research program on ELF and have isolated few interesting bioactive poliketides from ELF of three lichen species available in Sri Lanka. They have shown great potential to be a source for novel bioactive natural products. The objectives of this study were isolation and identification of bioactive compounds of the endolichenic fungus, Curvularia trifolii isolated from the lichen Usnea species. In a continuation of our chemical investigations in search of secondary metabolites of endolichenic fungi with medicinal value led to the isolation of few bioactive compounds. In this present study, C. trifolii was grown in large scale and incubated at room temperature for 10 days. The metabolites were extracted into ethyl acetate (EtOAc). Antibacterial, anticancer and insecticidal activities of the EtOAc extract were evaluated using in-vitro bioassays. The EtOAc extract was subjected to a silica gel column chromatography resulting, one major compound with high bioactivities. The isolated pure white crystalline compound was identified as 1,14-dihydroxy-6-methyl-6,7,8,9,10,10,14,14 -octahydro-1H-benzo[f][1] oxacyclododecin-4(13H)-one using 1H, 13C NMR, 2D NMR and MS data. The compound was found to possess antibacterial activity against three test pathogens, anticancer activity at (NCIH-460), (MCF-7), (SF-268), (PC3M), and (MDA-MB-231) cell lines and insecticidal activity.
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    Isolation of bioactive secondary metabolites from the endolichenic fungi, Neosartorya sp. inhabiting the lichen Parmotrema sp. in Sri Lanka
    (Faculty of Graduate Studies, University of Kelaniya, 2015) Manthrirathna, M.A.T.P.; Kandiah, R.; Gunasekara, D.S.; Paranagama, P.A.
    Natural products are a potential source of novel pharmaceutical agents. Therefore, isolation and identification of bioactive compounds from organisms adapted to various biotopes and unraveling their bioactivities in search for new pharmacophores has a mounting interest. Fungi are known to be prominent producers of useful metabolites. Endolichenic fungi (ELF) that occur asymptomatically within the lichen thalli are one of the ecological groups of fungi. ELF in Sri Lanka remain almost unexplored as a source of useful bioactive compounds. The objective of this study is to isolate bioactive secondary metabolites from ELF Neosartorya sp. isolated from Parmotrema sp. that occur in Hakgala Botanical Garden. ELF Neosartorya sp. was cultivated on 48 PDA plates and incubated at room temperature. Secondary metabolites were extracted into ethyl acetate from 9 days old cultures. Antibacterial activity of the crude extract was evaluated against Bacillus subtilis (BS) and Staphylococcus aureus (SA) using agar well diffusion method. Standard antibiotic Azithromycin was used as the positive control and Dimethyl sulfoxide as the negative control. Since the crude extract showed antibacterial activity against both BS and SA, it was partitioned with hexane, chloroform (CHCl3) and aqueous methanol. All three fractions showed activity against SA, with the CHCl3 fraction having higher activity compared to the other two fractions. Chloroform and methanol fractions showed significant activity against BS, while CHCl3 fraction showed activity comparable with Azithromycin. Chloroform fraction of Neosartorya sp. was further fractionated using bio-assay guided fractionation (silica gel column chromatography). Pure compounds were isolated using preparative TLC. One major pure compound was isolated from CHCl3 fraction and the characterization still in progress.