Chemistry
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Item Variation of catechin and caffeine content in exotic collection of tea [Camellia sinensis (L.) O. Kuntze] in Sri Lanka and potential implication in breeding cultivars with enhanced quality and medicinal properties(Food Chemistry Advances, 2022) Kottawa-Arachchi, J. D.; Ranatunga, M.A.B.; Amarakoon, A.M.T.; Gunasekare, M.T.K.; Attanayake, R.N.; Sharma, R.K.; Chaudhary, H.K.; Sood, V.K.; Katoch, R.; Banyal, D.K.; Piyasena, K.G.M.P.; Edirisinghe, E.N.U.Tea leaves are rich in diverse metabolites with medicinal importance. The quality of made tea is largely depended on the qualitative and quantitative attributes of key metabolites. The aim of the present study was to quantify flavan-3-ols and caffeine of exotic tea germplam and explore the medicinal properties. Fresh leaf flavan-3-ols; catechin, epicatechin (EC), epicatechin gallate (ECg), epigallocatechin (EGC) and epigallocatechin gallate (EGCg), caffeine and gallic acid of 131 accessions (87 exotic and 44 improved cultivars) were performed by High Performance Liquid Chromatography. Variations in metabolites among cultivars as well as between seasons were determined. Among the flavan-3-ols, EGCg was the most abundant followed by EGC, ECg and EC. Hierarchical clustering of 131 accessions based on metabolite diversity resulted two major clusters. Indian introductions clustered with well-known high quality cultivars indicating the potential utilization of high quality black tea production. Exotic accessions with low caffeine contents (< 20 mg g−1) were grouped separate cluster indicating the promising genetic resources for the development of low caffeine tea. Present study revealed that selected exotic tea accessions rich in bioactive compounds such as catechins and caffeine content could be utilized in producing speciality teas with enhanced quality and medicinal properties.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 Antioxidant, a-Amylase Inhibitory Activities and Photoprotective Properties of Peels of Nephelium Lappaceum Linn. (Malwana Special)(Oriental Journal of Chemistry, 2021) Binuwangi, A.K.D.M.; Perera, M.P.J.; Silva, A.A.G.; Attanayake, R.N.; Rajapakse, C.S.K.This study focused on evaluation of antioxidant, α-amylase inhibitory activities and photo protective properties of peels of Nephelium lappaceum Linn. (rambutan); Malwana special. Methanolic extract of peels was sequentially partitioned in hexane, dichloromethane (DCM) and aqueous methanol. The methanol extract showed a significantly (p greater then 0.05) higher DPPH radical scavenging activity than that of butylated hydroxytoluene. Among the fractions, the highest total phenolic content (TPC) was found in the aqueous methanol fraction. DCM and aqueous methanol fractions were rich in flavonoids. In vitro α-amylase inhibitory activity of the aqueous methanol fraction was also significantly higher than the standard drug, acarbose. Partially purified aqueous methanol fraction of rambutan peels exhibited UV-B absorption with a moderate solar protection factor. The results revealed that the peels of Nephelium lappaceum Linn., Malwana special can be considered as a promising source for the development of natural antioxidant, cosmeceutical sunscreen and antidiabetic agents.Item Decaying Hardwood Associated Fungi Showing Signatures of Polyethylene Degradation(BioResources, 2021) Perera, P.; Deraniyagala, A.S.; Mahawaththagea, M.P.S.; Herath, H.; Rajapakse, C.S.K.; Wijesinghe, P.; Attanayake, R.N.The involvement of wood decay fungi and the importance of their enzymes in polyethylene degradation is well documented. Therefore, decay-resistant hardwood associated fungi should be better degraders with their versatile enzymatic systems. In the current study, decaying hardwood associated fungi were isolated and their ability to degrade low-density polyethylene (LDPE) was assessed. Thirty-three isolates were identified by sequencing the internal transcribed spacer region of nuclear ribosomal DNA. Randomly selected isolates were tested for laccase producing abilities. Three species were selected to test their potentials in LDPE sheet degradation. Fungi were incubated in Czapek-Dox broth containing 20-micron LDPE sheets at room temperature for 60 days. The biodegradation signatures were assessed by analyzing the changes in structural characteristics of LDPE using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), percent reduction of tensile properties, and weight loss. FTIR analysis revealed changes in certain functional groups compared with the control, indicating chemical changes resulting from the treatment. LDPE sheets incubated with fungi showed cracks and holes under SEM analysis, percent reduction in tensile properties, and weight loss, which are the signatures of degradation. This study revealed that the hardwood decaying basidiomycetes, Phlebiopsis flavidoalba, Schizophyllum commune, and Phanerodontia chrysosporium have the potential for in vitro LDPE degradation.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 Potential Antibacterial Secondary Metabolites froe an Enadolichenic Fungus Inhabiting a Lichen Collected from Negombo Lagoon, Sri Lanka(International Postgraduate Research Conference 2019, 2019) Weerasinghe, W.R.H.; Gunawardhana, M.H.A.Y.; Wickramarachchi, S.; Attanayake, R.N.; Weerakoon, G.; Paranagama, P.A.With the revelation of intriguing bioactive properties from natural sources, the thirst to investigate more into the mysteries of nature has immensely expanded. Endolichenic fungi (ELF) became an interesting source during the recent past in this search for novel bioactive compounds and literature sources provide evidence of many such bioactive compounds isolated from these interesting organisms. These ELF asymptomatically live inside the lichen thallus which is formed by the symbiotic relationship of fungi with an algae or a cyanobacteria. A total of 31 lichens were collected from mangrove plants in Negombo lagoon and their molecular identification revealed that they belonged 10 different species. Healthy lichen thalli were surface sterilized and were cut into small segments and plated on 2% Malt Extract Agar (MEA) medium supplemented with 0.01% streptomycin in order to obtain ELF. The obtained pure cultures of ELF were identified using molecular techniques. DNA was extracted using CTAB method and its quality and quantity were determined by agarose gel electrophoresis. DNA was diluted accordingly and was subjected to Polymerase Chain Reaction (PCR) to amplify fungal ITS rDNA region using universal primers. PCR amplification was tested using agarose gel electrophoresis and the full sequences were obtained. Ethyl acetate crude extracts of 18 such identified ELF strains were subjected to anti-bacterial assay against Escherichia coli and Staphylococcus aureus using agar well diffusion method. The species Xylariafeejeensis isolated from the lichal Graphis librata showed remarkable activity against the two bacterial strains on par with the positive control Azithromycin. The assay was carried out using 100 gl of the extract and the positive control (5 mg/ml). The inhibition zone diameters (in cm) against E coli and S. aureus for the ftmgal crude were 1.9 and 2.2 respectively and for Azithromycin was 2.2 against both. In order to isolate the active compounds, a larger crude of the same was obtained and partitioned into Hexane, Chloroform and tvlethanol fractions based on polarity. The assay results for the three fractions revealed that only Hexane and Chloroform fractions possessed anti-bacterial potentiality. Subsequently, silica gel normal phase column chromatography was performed for fur-tha- fractionation. Collected 6 fractions from the column for Chloroform fraction showed inhibition diameters of 1.9, 1.9, 1.5, 1.2, 1.3, 1.1 against E. coli comparable with 2.2 of Azithromycin and 2.4, 2.2, I .4, 0.0, 03,0.0 against S. aureus comparable with 2.5 of Azithromycin. The fraction 1 and 2 showed highest activity against both bacterial strains and fraction 4 and 6 showed lowest activity against E. coli and none against S. aureus. Further isolation is being carried out for active fractions and the structures of obtaining active compounds will be elucidated using spectroscopic methods.