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Author: search.filters.author.Amarasinghe, M.D.

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    Anti-oxidant activity of selected endo lichenic fungi (ELF) in mangrove ecosystem of Puttalam lagoon.
    (International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Maduranga, H.A.K.; Attanayake, R.N.; Amarasinghe, M.D.; Weerakoon, G.; Paranagama, P.A.
    Natural products based drug development has become an attractive area of research since there are limited options available to treat certain non-infectious diseases such as diabetes. Among these natural products, it has been reported that secondary metabolites of endolichenic fungi (ELF), have the ability to produce promising bioactive compounds. The objectives of this research were to isolate and identify ELF inhabiting mangroves in Puttalam lagoon, Sri Lanka using classical and DNA barcoding approach and to determine anti-oxidant activity of their secondary metabolites. Lichen hosts were collected from Puttalam lagoon in two different sites near, Athathale and around the NARA institute. The ELF were isolated following a standard procedure: a small piece of the thallus was surface sterilized, cut into pieces and dried on sterilized filter papers and then placed on malt extract agar in Petri dishes and incubated at room temperature (28 ⁰C – 30 ⁰C ) . Once pure cultures were obtained, seven isolates were randomly selected for DNA extraction following standard procedures. Quality of DNA was checked by agarose gel electrophoresis. Fungal internal transcribed spacer (ITS) region was amplified using polymerase chain reaction (PCR) with universal ITS 1 and ITS 4 primers and PCR products were sequenced using Sanger dideoxy chain-termination technology. DNA sequences were edited using BioEdit software and compared with the available sequences in the GenBank using Basic Local Sequence Alignment Search Tool (BLAST). In addition, morphological characterization of each fungal isolate was also carried out. Secondary metabolites from each isolate were extracted with ethylacetate separately and the solvent was evaporated under reduced pressure to obtain the crude extract. Free radical scavenging activity of the extracts were evaluated using 2, 2-diphenyl-1-picrylhydrdrazyl (DPPH) assay. Based on the highest sequence similarity to the GenBank sequences, isolates were identified as Diaporthe arengae (98 %), Neurospora crassa (100%), Lasiodiplodia theobromae (100 %), Schizophyllum commune (98 %), Diaporthe musigena (98 %), Hypoxylon anthochroum (98 %) and Nigrospora sphaerica (98%). IC50 values of extracts of Diaporthe arengae, Neurospora crassa and Lasiodiplodia theobromae were 375.9± 0.062μg/mL, 304.9±0.057 μg/mL and 211.2± 0.086 μg/mL respectively. Since percent inhibitions of the rest of the isolates were less than 50 % in the test doses, IC50 values were not calculated. All of the values were compared with standard Butylated Hydroxy Toluene (BHT) (IC50=108.0±0.072). Out of the seven ELF tested, L. theobromae showed the highest DPPH radical scavenging activity. Further testing of the rest of the isolates are being carried out and ELF may provide a good source of antioxidants for biotechnological applications.
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    Annual fluctuations in populations of sea urchin Stomopneustes variolaris (Lamarck. 1816) in two rocky shores of southern Sri Lanka
    (Sri Lanka Association for Fisheries and Aquatic Resources, 2012) Thilakarathna, R.M.G.N.; Jayakody, S.; Amarasinghe, M.D.
    Sea urchins play a key role in rocky shore habitats as grazers. They form urchin fronts and extensively graze on macro algae resulting in regions of barrens and restructuring the habitat. The population status of Stomopneustes var/alaris (Lamarck, 1816) of Phylum: Echinodermata Class: Echinoidea, the most abundant sea urchin species in intertidal zones of Sri Lanka was investigated from June 2008 to May 2009. The study evaluated the density of S. varialaris and the influences of macro algae cover in two rocky shore areas from Hikkaduwa (legally protected) and Ahangama (legally unprotected) in Southern Province. Three habitats (near shore, intermediate and splash) were selected in each site. Line transect and quadrate (50X50cm) sampling methods were used to measure macroalgae cover whilst S. variolaris density of each habitat was measured using belt transect method (10m X O.5m) every month. Mean percentage occurrence of algae and density of S. variolaris were analyzed using multivariate techniques and general linear models. Accordingly, Canonical Variate Analysis of flora confirmed the distinctiveness of the three habitats in relation to floral cover mainly due to differences in the dispersion of Hypnea pannasa and Graciaria sp. sp. in Hikkaduwa and due to Padina sp., Ulva lactuca and Jania ungulata in Ahangama. Ninety nine percent of the variation was explained by axes 1 and 2 in both Hikkaduwa and Ahangama. Mean densities of S. variolaris recorded for Hikkaduwa and Ahangama were 1.65:t0.46 m.l and 0.71 :t 0.22 m'l respectively and Hikkaduwa had a higher density compared to Ahangama (p< 0.05). In Hikkaduwa the highest mean density (3.56 :t 1.48 m'l) was recorded in splash zone (p < 0.05), whilst in Ahangama the highest mean density (1.42:t 0.53 m'l) was recorded in near shore habitat (p< 0.05). A non significant peak density was observed in the months of April and July in Hikkaduwa, and October in Ahangama. Results indicated S. variolaris inhabiting in higher numbers towards the sea in Hikkaduwa but in Ahangama near to coast, perhaps a response to greater disturbance in Hikkaduwa due to visitors.
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    A preliminary study on impact of agrochemical-free rice cultivation on soil characteristics
    (Sri Lanka Association for the Advancement of Science, 2015) Gamage, P.G.I.J.; Amarasinghe, M.D.
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    Chronic Kidney Disease of Unknown Etiology (CKDu) and Arsenic in Groundwater in Sri Lanka
    (Water Resources Board, Colombo, 2011) Jayasumana, C.; Paranagama, P.A.; Amarasinghe, M.D.
    In recent years a significant increase in patients of Chronic Kidney Disease of unknown etiology (CKDu) has been observed in some parts of Sri Lanka, especially in Medawachchiya, Padaviya, Kebitigolawa, Medirigiriya (North Central Province), Nikawewa (North Western Province), Dehiattakandiya (Eastern Province) and Giradurukotte (Uva Province). Uniqueness of this disease is that its victims do not share the same history as other kidney patients who have had it either due to diabetes, high blood pressure, past snake bites or urinary tract infections. Etiology of this disease has since been attributed to a range of causes, including presence of the heavy metal cadmium in water that would potentially have introduced to water from inorganic fertilizer used in paddy fields, presence of excessive amounts of fluoride in drinking water and prevalent use of low quality aluminum utensils, presence of toxins produced by microorganisms such as cynobacteria in water. Despite the effort of about 60 researchers including those who were funded by WHO (World Health Organization) over the last decade, none of these hypotheses have been supported with evidence; in fact, the data available prove them not to be the cause. The causative factors and etiology of this chronic kidney disease therefore is still considered uncertain or unknown and abbreviated as CKDu with recommendations of the National Research Programme for CKD of the Ministry of Health in Sri Lanka.
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    A preliminary study on nutritional quality of an indigenous rice variety (Kuruluthuda) and a hybrid rice variety (BG 358)
    (Institute of Biology, Sri Lanka, 2015) Gamage, P.G.I.J.; Amarasinghe, M.D.
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    Nitrate, phosphate and sulfate concentrations of well water in CKDu endemic areas and non-endemic areas and their relation to water hardness
    (Sri Lanka Association for the Advancement of Science, 2013) Fonseka, S.I.; Amarasinghe, M.D.; Paranagama, P.A.
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    Preliminary investigations on the groundwater hardness in Polpithigama and use of selected plant parts for hardness reduction
    (Sri Lanka Association for the Advancement of Science, 2013) Jayasiri, U.D.S.C.; Amarasinghe, M.D.
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    Bioconcentraton of metals in edible aquatic plants from a Sri Lankan freshwater wetland
    (Sri Lanka Association for Fisheries and Aquatic Resources, 2008) Amarasinghe, M.D.; Nirbadha, K.G.S.; Liyanage, J.A.
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    Effect of vegetation structure on primary productivity of mangroves at Kadolkele in Negombo lagoon
    (Sri Lanka Association for Fisheries and Aquatic Resources, 2006) Jayakodi, J.M.A.L.; Amarasinghe, M.D.; Pahalawattaarachchi, V.