Chemistry
Permanent URI for this collectionhttp://repository.kln.ac.lk/handle/123456789/3748
Browse
6 results
Search Results
Item Antibacterial Polyketide from Lasiodiplodia theobromae and Pyrenula bahiana on Mangrove Ecosystems in Puttalam Lagoon, Sri Lanka(Asian Journal of Chemistry, 2022) Paranagama, P.A.; Santhirasegaram, S.; Wickramarachchi, S.R.; Attanayake, R.N.; Weerakoon, G.; Maduranga, K.Lasiodiplodia theobromae is one of the frequently isolated fast growing endolichenic fungus. This fungus was isolated from the lichen host, Pyrenula bahiana collected from the mangrove ecosystems in Puttlam lagoon and its identification was confirmed based on rDNA-ITS sequence homology. Secondary metabolites of L. theobromae were extracted into ethyl acetate and subjected to antibacterial assay against Escherichia coli (ATCC25922), Staphylococcus aureus (ATCC25923) and Bacillus subtilis (ATCC6051). Crude extract at a concentration of 6.8 μg/mL showed good antibacterial activity against the bacterial strain S. aureus compared with the activity of the standard azithromycin at a concentration of 5.0 μg/mL. Active crude extract was partitioned to obtain methanol, hexane and chloroform fractions. Chloroform fraction showed the highest activity to S. aureus out of three fractions. This fraction was subjected to bioassay-guided separation on silica gel column chromatography to isolate bioactive pure compounds. The bioactive pure compound was identified as (3R)-de-O-methyllasiodiplodin using LC-MS, 1D and 2D NMR spectroscopy.Item Antimicrobial Compounds Isolated from Endolichenic Fungi: A Review(Molecules 2021, 2021) Wethalawe, A.N.; Alwis, Y.V.; Udukala, D.N.; Paranagama, P.A.A lichen is a symbiotic relationship between a fungus and a photosynthetic organism, which is algae or cyanobacteria. Endolichenic fungi are a group of microfungi that resides asymptomatically within the thalli of lichens. Endolichenic fungi can be recognized as luxuriant metabolic artists that produce propitious bioactive secondary metabolites. More than any other time, there is a worldwide search for new antibiotics due to the alarming increase in microbial resistance against the currently available therapeutics. Even though a few antimicrobial compounds have been isolated from endolichenic fungi, most of them have moderate activities, implying the need for further structural optimizations. Recognizing this timely need and the significance of endolichenic fungi as a promising source of antimicrobial compounds, the activity, sources and the structures of 31 antibacterial compounds, 58 antifungal compounds, two antiviral compounds and one antiplasmodial (antimalarial) compound are summarized in this review. In addition, an overview of the common scaffolds and structural features leading to the corresponding antimicrobial properties is provided as an aid for future studies. The current challenges and major drawbacks of research related to endolichenic fungi and the remedies for them have been suggested.Item Pheromone baited biopesticide for control of Leucinodes orbonalis Guenee in brinjal plant(Frontiers in Bioscience, Elite, 2020) Nusra, M.S.F.; Paranagama, P.A.; Amarasinghe, L.D.; Udukala, D.N.Leucinodes orbonalis Guenee, Brinjal fruit and shoot borer (BFSB), is the major pest on brinjal world wide. Larvae of this pest cause the damage; which at initial stages adversely affect the shoot growth, and in later stages diminish fruit quality. Spraying of insecticides is the main pest control method. This has been absolutely ineffective due to concealed habit of the larvae. Such a phenomenon apprehends to the development of insecticides resistance which demands continuously increasing doses. Manipulating the insect behavior using semiochemicals could be an opportunity for better management of insect pest. Application of BFSB sex pheromone components (E)-11-hexadecenyl acetate (E11-16: Ac) alone or in combination with (E)-11-hexadecen-1-ol (E11-16: OH) in traps can be used to suppress the populating growth. Goal-oriented interdisciplinary research on semiochemicals for sound administration of BFSB will depend on a better understanding of the key chemical ecology stimuli of relevance to the pest.Item A Novel Cytotoxic Compound From the Endolichenic Fungus, Xylaria psidii Inhabiting the Lichen, Amandinea medusulina(Natural Product Communication, 2020) Santhirasegaram, S.; Wickramarachchi, P.A.S.R.; Attanayake, R.N.; Weerakoon, G.; Samarakoon, S.; Wijeratne, K.; Paranagama, P.A.The lichen host, Amandinea medusulina, collected from mangrove habitats in Sri Lanka, and its associated endolichenic fungi were isolated and identified by rDNA-ITS sequence analysis and morphological features. One of the fungal strains frequently isolated from the lichen thalli was identified as Xylaria psidii. This study aimed at the isolation and identification of the cytotoxic compounds present in this fungus. Secondary metabolites of X. psidii were first extracted into ethyl acetate and subsequently subjected to bioassay-guided fractionation to isolate the bioactive compounds. Sulforhodamine B assay against a lung cancer (NCI-H292) cell line was used to determine the differential cytotoxic activity. Bioassay-guided fractionation led to the isolation of an active compound, SS/02/29/08, showing moderate cytotoxicity (IC50 = 27.2 µg/mL). Its structure was elucidated by IR, 1D- and 2D-NMR, and 13C-NMR spectrophotometry and MS, in combination with HRMS, 13C NMR, HSQC, HMBC, and DQF-COSY. The structure of SS/02/29/08 was determined as (Z)-3-{(3-acetyl-2-hydroxyphenyl)diazenyl}-2,4-dihydroxybenzaldehyde and identified as a new compound. This novel compound has promising differential cytotoxic activity against human lung cancer cell line (NCI-H292).Item Exploring bioactive compounds in the endolichenic fungus, Xylaria feejeensis, inhabiting the lichen, Graphis librata, collected from Negombo lagoon, Sri Lanka(Proceedings of the 1st International Conference on Frontiers in Chemical Technology, Institute of Chemistry Ceylon, 2020) Gunawardhana, M.H.A.Y.; Wickramarachchi, P.A.S.R.; Weerasinghe, W.R.H.; Paranagama, P.A.The accelerating pharmaceutical problem ofbacteria growing resistant to existing antibrotics forces the scientific community to search for new antibacterial compounds for antibiotic drug development. I-iterature reveals that Sri Lankan mangrove inhabiting endolichenic fungal (ELF) population is rich in nrany such bioactive compounds- Previously isolated and cultured ELF, Xylaria feejeensis; ftom the lichen Graphis librata inhabiting in the mangrove phnt Rhizophora mucronata was culrured on 60 large Potato dextrose agar medium containing petri dishes and incubated for 14 days at room temperature. After extracting secondary metabolites to ethyl acetate (EA) the resulted crude extract was tested for its antibacterial and antioxidant activity. EA crude extract shou,ed negligible antioxidant activity in DPPH radical scavenging assay hence this assay was not proceeded further. The activity ofcrude extract (5 mg/ml) agatnstEscherichia coli (ATCC25922), Staphylococcus aureus (NCC25923) utd Bacillus subtilis (ATCC605I) was tested using agar well diffirsion antibacterial assay. An inhibition zone diameter of 1.9 cm, 2.2 cm, ar,d 2.2 cm against three bacterial strains with Azithromycin positive control (5 mg/ml) 2.2 cm,2.2 cm and 2.3 cm was observed respectively. By Partitioning of EA crude extract resulted two antibacterial active hexane and chloroform fractions and one antibacterial inactive 607o methanol in water fraction. Hexane fraction showed the highest antibacterial activity with inhibition diameter zone of 2.6 cm against E.coll with 2.6 cm diameter of inhibition zone for positive control. Further purification ofhexane fraction was performed by normal phase column chromatography and 4 fractions were resulted. The highest polar fraction showed L4, 2.landl.TcmdiameterinhibitionzonesofgroMhofE.coli,S. aureusutdB.sr.rbtillscomparablewith 2.2 cm Azithromycin. The other 3 fractions showed no antibacterial activity against these bacterial strains. Results suggest that further purification of active fraction and structure elucidation might result in new antibiotic lead compounds.Item Antibacterial activity of the partitioned fractions of endolichenic fungus Xylaria feejeensis collected from the mangrove plant Rhizophora mucronate in Negambo Lagoon, Sri Lanka(Proceedings of 7th Ruhuna International Science & Technology Conference, 2020) Gunawardhana, M.H.A.Y.; Wicramarachchi, S.; Weerasinghe, W.R.H.; Paranagama, P.A.Endolichenic fungi (ELF) are known for biosynthesizing secondary metabolites with antifungal, cytotoxic, antioxidant and antibacterial activity to protect their lichen against radiation, microbial invasions and harsh surrounding environments. Mangrove plants in Negombo lagoon is a niche for a diverse range of lichens. The ELF, Xylariafeejeensis from the lichen, Graphis librata which develops on the mangrove plant, Rhizophora mucronata in Negombo lagoon was previously isolated and identified by the research group at the University of Kelaniya. The objective of this study was to determine the antibacterial activity of the secondary metabolites of X feejeensis. A pure culture Of X. feejeensis on potato dextrose agar plates (60) was incubated for 14 days and secondary metabolites were extracted to ethyl acetate by shaking overnight. The ethyl acetate crude extract (5 mg/ml, 100 gl„) was subjected to agar well diffusion anti-bacterial assay against Escherichia coli (ATCC25922), Staphylococcus aureus (ATCC25923) and Bacillus subtilis (ATCC6051) with Azithromycin positive control and it showed above 85% inhibition of growth for all three bacteria. Hence the crude extract (8.58 g) was partitioned in hexane, chloroform and 60% methanol in water (v/v) and tested for antibacterial activity. Hexane fraction showed the highest inhibition of growth of E. coli with 100% inhibition and chloroform fraction showed the highest inhibition of the groMth of S. aureus with 88.5% inhibitioh whereas methanol fraction showed no antibacterial activity. The results suggest that X. feejeensis produces secondary metabolites with high antibacterial activity. Further purification of hexane and chloroform fractions may results in antibacterial drug leads.