iPURSE 2016

Permanent URI for this collectionhttps://ir.lib.pdn.ac.lk/handle/20.500.14444/40

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Connectivity matrix representation of graphs obtained by graph operations on complete bipartite graphs
(Postgraduate Institute of Science, University of Peradeniya, Sri Lanka, 2021-10-29) Gunawardana, M.G.U.S.; Perera, A.A.I.
The connectivity matrix is an adjacency matrix with the property that each cell representing the connection between two nodes receives a value of one. Each cell that does not represent a direct connection gets a value of zero. Connectivity matrices are used in real-world applications such as finding the network tolerance of a network and brain connectivity. Our study mainly focuses on obtaining simple matrix representations for resulting graphs of finite summation and multiplication of 𝐾𝑚,𝑚. In our previous work, we have shown that the resulting graph of the product of 𝑛 copies of complete bipartite graphs (𝐾𝑚,𝑚) 𝑛 is also a complete bipartite graph, and the number of edges adjacent to each vertex is given by 2 𝑛−1 × 𝑚𝑛 and the summation of 𝑛 copies of 𝐾𝑚,𝑚 is not a complete bipartite graph, and the number of edges adjacent to one vertex is given by 𝑚(2𝑛 − 1). These resulting graphs are complicated. In our work, we have shown that the matrix representation of 𝐾𝑚,𝑚 is the 𝑚 × 𝑚 square matrix (𝑀𝑚) with all entries equal to 𝑀, where 𝑀 = [ 0 1 1 0 ] which is the matrix representation of 𝐾1,1. Matrix representation of (𝐾𝑚,𝑚) 𝑛 is a square matrix of order (2 𝑛−1𝑚𝑛 × 2 𝑛−1𝑚𝑛 ) with all entries equal to 𝑀 and this result is proved by mathematical induction where 𝑚 is the number of vertices in one partite set or degree of one vertex and 𝑛 represents the number of copies of 𝐾𝑚,𝑚. The matrix representation of the graph obtained by adding 𝑛 copies of 𝐾𝑚,𝑚 is, [ 𝑀𝑚 𝐽2𝑚 … 𝐽2𝑚 𝐽2𝑚 ⋱ ⋯ 𝐽2𝑚 ⋮ ⋮ ⋱ ⋮ 𝐽2𝑚 𝐽2𝑚 ⋯ 𝐽2𝑚 ], where 𝐽2𝑚 is the 2𝑚 × 2𝑚 matrix with all entries equal to 1. This result is also proved using mathematical induction. As an application, we plan to apply these theorems to prepare aeroplane routing plans.
Effect of some plant extracts in reducing oxidation of selected edible oils during deep frying
(University of Peradeniya, Sri Lanka, 2016-11-05) Jayathilake, R.R.G.D.K.; Hemachandra, T.P.; Madhujith, T.
The repeated use of edible oils leads to oxidative degradation of lipids which results in the development of objectionable odours, flavours, colours and more importantly, generates toxicants. The objective of the present study was to examine the efficacy of natural anti- oxidative extracts obtained from rosemary, oregano and pomegranate peel in mitigating the oxidation of coconut oil (CO), virgin coconut oil (VCO) and sunflower oil (SO). These edible oils were used for frying standard-sized potato strips in the presence of three different anti- oxidative extracts; namely, pomegranate peel powder, oregano and rosemary extracts, at 2% (w/w) level. A sample of oil (10 mL) was collected into a vial, flushed with nitrogen and stored at -18⁰C until analysis. Frying was repeated twice more with the same oil. Oil devoid of any extract was used as the control. The samples collected were analysed for peroxide value (PV) and thiobarbituric acid reactive substances (TBARS). Results revealed that both PV and TBARS values gradually increased with the frying cycle in all oil systems tested, indicating a gradual oxidation of oils with time. A significant (P < 0.05) inhibition of oxidation due to incorporation of additives was observed in all oils. The stability of oils increased in the order: sunflower oil < sesame oil < virgin coconut oil. Generation of primary as well as secondary oxidative products was higher in sunflower oil (PV: 1.33 - 5.38 meq/kg, TBARS: 68.27 - 104.12 meq MA/kg) than in SSO and VCO. The inhibition exerted by anti- oxidative extracts against development of primary oxidative products as measured by PV was significantly (P < 0.05) higher in SO followed by VCO and SSO. The inhibition exerted against development of TBARS was higher in VCO as compared to SO and SSO. It can be concluded that anti-oxidative extracts such as pomegranate peel powder, oregano and rosemary can be effectively used to mitigate oxidation of edible oils during accelerated storage.
Production planning for a dairy product: A case study in Jaffna
(University of Peradeniya, Sri Lanka, 2016-11-05) Sharachie, J.; Daundasekera, W.B.
Dairy industry has a mature market within Sri Lankan economy. This study investigated the distributions of the demand of dairy production and prices of raw-materials to find the optimum amount of the dairy production which gives the maximum annual profit. A dairy industry which is located in Jaffna was chosen for this study. Despite having a variety of products which are manufactured in this industry, lolly which is a type of sweet ice juice made of milk, was selected due to its popularity among customers and it is considered as a strategic product to the industry. The collected data consist of customer demands, selling price, requirements of ingredients, raw-material prices, labour charges, electricity cost, holding cost and shortage cost. Data were collected in the time period from January 2011 to December 2015. The industry was looking for a production planning strategy which helps to gain a considerable annual profit. The collected data are analyzed in order to explore the distribution of the monthly demand for lolly and distribution of raw-material prices. Simulation technique was used to estimate the demand and raw-material prices considering their probability distributions. Monthly unit production cost, shortage cost and holding cost were calculated. This information was used to formulate a linear programming model for aggregate planning in which the optimum production for maximum annual profit could be obtained. The Solver built-in optimization tool of Microsoft Excel was used to find the maximum profit. The decision variables are required to be integer. Therefore, the number of products obtained could be approximated to integer quantities without affecting the implementation. The study showed that the implementation of the results can increase the net profit by selling lolly. Monthly demand follows a normal distribution. Raw-material price follows a uniform distribution. Findings from this work could serve as useful information to the management of the industry in the formation of production strategies for its lolly dairy product.
Modification of apatite from Eppawala rock phosphate deposit (ERPD) to be used in advanced materials: Removal of fluoride and particle size reduction
(University of Peradeniya, Sri Lanka, 2016-11-05) Gamagedara, T.P.; Bandara, H.M.N.; Rajapakse, R.M.G.
Apatite has more important applications as a vital raw material in orthopedics, dentistry, etc than its traditional use as a fertilizer. Eppawala apatites (EpAp) are chemically identical and basically composed of chlorofluoroapatites and weight percentage of fluoride in EpAp was found as 1.5 – 2.1%. To be used in advanced materials, purification of EpAp will be advantageous. Therefore, in this study, heat treatment of EpAp was carried out to investigate the removal of fluoride and effect on particle size was studied as particle size reduction is beneficial to enhance certain properties. Physically separated apatites from ERPD were ball milled and heated at different temperatures for different time periods using a thermo gravimetric analyzer (TGA) with monitoring the removal using SPADNS spectrophotometric method as well the weight loss and heat flow, using TGA and DSC curves respectively. TGA curve of EpAp shows there is a weight loss upon heating after reaching the temperature 700 ⁰C. According to the SPANDS spectrophotometric analysis, about 8% offluoride can be removed by heating EpAp to 900 ⁰C for 1 hour. According to the TGA curves, percent removal of fluoride can be increased, when sample was kept at 900-1000 ⁰C for an extended time period. Shifting of broad endothermic peak around 600⁰C, towards higher temperatures and decrease in percent removal with progressive TGA runs for a sample, indicate the difficulty of removal of interior fluorides in the EpAp crystal structure. Powder X-ray diffraction (PXRD) patterns reveal that heat treatment does not effect on the apatite crystal structure. However, calculations of particle sizes along a-axis and c-axis and SEM images show reductions in particle size and some differences in the shapes upon heating. Particle size reduction may be due to the removal of fluoride from their lattice sites of EpAp lattice leading to the breakdown of extended EpAp crystal structures. Thus, in this simple heating method, F⁻removal from EpAp can be achieved around 700 ⁰ C and upon increasing the temperature and duration, the amount removed can be increased and particle size can be reduced. In addition, crystal structure can be maintained up to the studied temperature (~1000 ⁰ C).
Synthesis and characterization of plant based thiophene and 3-hexylthiophene copolymers
(University of Peradeniya, Sri Lanka, 2016-11-05) Kodithuwakku, U.; Prashantha, M.A.B.; Ratnaweera, D.R.
Polythiophene and its derivatives have become more desirable due to their applications in various fields. These applications arise due to their inherent properties, such as optical and electronic conductive properties; as well as thermal and environmental stability. Precursors of polythiophenes are generally obtained from petroleum by-products, which are non-renewable. It has been reported that precursors of polythiophenes and its derivatives are naturally available in different types of Tagetes species such as Tagetes erecta, Tagetes tenuifolia, etc. A number of thiophene derivatives such as 2, 2’:5’, 2’’-terthienyl (Alpha-T), 5- (3-buten-1-ynyl)-2, 20-bithienyl (BBT), 5-(4-hydroxy-1-butynyl)-2, 20-bithienyl (BBTOH), and 5-(4-acetoxy-1-butynyl)-2, 20-bithienyl (BBTOAc), were found and identified, specifically in the roots of Tagetes species. The current study reports the polymerization of the extracted thiophene derivatives from Tagetes erecta and 3-hexylthiophene (3HT) to obtain a random copolymer of poly (thiophenes-3-hexylthiophene). The extracted thiophene derivatives were partially purified and characterized. The mixture of plant based thiophenes and commercial 3HT with various weight compositions were selectively polymerized on the direct one-step chemical oxidative free radical polymerization to obtain co-polymers. Structural characterization of the synthetic products was done using Fourier Transformation Infrared, Proton Nuclear Magnetic Resonance, Ultra Violet Visible and X-ray Diffraction techniques. Homopolymers of polythiophene obtained from plant based thiophenes have limited processability of solar cells due to poor solubility in common organic solvents. 'However, a significant progress of the solubility was observed with copolymers having partial contribution of 3HT.
Structures and properties of naphthoquinones produced by Monacrosporium ambrosium, an ectosymbiote of the shot hole borer beetle Xyleborus fornicatus
(University of Peradeniya, Sri Lanka, 2016-11-05) Kehelpannala, C.L.; Kumar, N.S.; Jayasinghe, L.; Araya, H.; Fujimoto, Y.
The fungus, Monacrosporium ambrosium (syn. Fusarium ambrosium) has a symbiotic association with the shot-hole borer beetle, Xyleborus fornicatus, an insect pest that causes serious damage to the tea (Camellia sinensis var. assamica) plantations in Sri Lanka. Here we report the isolation of six naphthoquinones produced by the fungus M. ambrosium and the biological activities of the crude extracts of the fungal culture. M. ambrosium was fermented in potato dextrose broth and medium was extracted with ethyl acetate (EtOAc) and the mycelium with EtOAc and methanol (MeOH). Chromatographic separation of the combined two EtOAc extracts (Extract A) afforded six pigmented naphthoquinones, identified as anhydrojavanicin, dihydroanhydrojavanicin, 7-acetonyl-5, 8-dihydroxy-6-methyl-1, 4- naphthoquinone, javanicin, anhydrofusarubin and solaniol. Extracts were screened for antifungal activity, brine shrimp lethality, lettuce seed germination assay and α-amylase inhibitory assay. Furthermore, the antifungal activity was examined against two endophytic fungi, Pestalotiopsis camelliae and Phoma multirostrata isolated from tea stems as well as three endophytic fungi, Bipolaris sorokiniana, Daldinia eschscholizii and Glomerella magna from Costus speciosus, Phyllanthus acidus and Piper betel respectively against M. ambrosium. Extract A was found to possess several compounds with antifungal activity against C. cladosporioides. The shoot and root elongation of lettuce seeds were found to be completely inhibited by the EtOAc extract of culture broth and EtOAc extract of mycelium at 250 and 1000 ppm, respectively. The root elongation was completely inhibited at 2000 ppm of MeOH extract of mycelium while complete inhibition of shoot elongation was observed at 4000 ppm. The extracts were found to be positive in the brine shrimp lethality LD₅₀ -702, 1395 and 993 ppm for the EtOAc extract of culture broth, EtOAc extract of mycelium and MeOH extract of mycelium, respectively. None of the extracts showed good activity in the α-amylase inhibitory activity assay. Extract A was found to inhibit the growth of two endophytic fungi P. camelliae (100% at 1000 ppm) and P. multirostrata (38.1% at 1000 ppm). M. ambrosium did not inhibit the growth of B. sorokiniana, D. eschscholtzii and G. magna. These results suggest that M. ambrosium produces antifungal naphthoquinones, which selectively inhibit the growth of two endophytic fungi living within tea stems.
Monitoring exposure of birds to heavy metals and arsenic in Bundala National Park, Sri Lanka: A preliminary study
(University of Peradeniya, Sri Lanka, 2016-11-05) Jayasena, N.U.A.; Kotagama, S.W.; Diyabalanage, S.; Hettiarachchi, I.M.; Chandrajith, R.
Feathers are used as a non-invasive method of monitoring exposure to toxic elements. Bundala National Park (BNP), in the Southern Province of Sri Lanka, a Ramsar site, is a wetland complex used by almost 200 species of resident and migrant wading birds as well as by other birds. Heavy metals and other contaminants accumulate in wetlands through agricultural runoff and atmospheric deposition. Our objectives were to monitor the exposure to heavy metals and arsenic in resident and migratory birds at BNP using feather samples and to determine the patterns of exposure among birds with different dietary habits. Feather samples (n=44) from 12 species (six migrants) were collected from birds captured during the National Bird Ringing Programme during migratory seasons in 2011 – 2013. Feathers were analysed by inductively coupled plasma mass-spectrometry (ICP-MS) for Hg, Cd, Pb and As. The range (mean ± S.E.) of Hg, Cd, Pb and As in tested samples were 0-8.20 (2.02 ± 0.27), 0- 1.88 (0.10 ± 0.05), 0-12.63 (2.18 ± 0.45) and 0.01-10.20 (0.94 ± 0.25) mg/kg respectively. The highest mean concentrations of Hg, Pb and As were recorded in three species of migrant waders which were 3.05 mg/kg (± 0.84) of Hg in Tringa totanus (n=10), 4.30 mg/kg (± 1.92) of Pb in Tringa stagnatilis (n=3) and 1.14 mg/kg (± 0.64) of As in Calidris ferruginea (n=4). Both resident passerines tested, Pycnonotus luteolus and Turdoides affinis (n=2 each), showed levels of contaminants that were higher than expected. Hg levels in P. luteolus and T. affinis were 1.20 (± 0.69) and 1.86 (± 1.21) mg/kg respectively. These two omnivorous species are at lower tropic levels than waders and less likely to bioaccumulate metals. This study shows that both migrant and resident birds of varying dietary habits at BNP are exposed to Hg, Cd, Pb and As. The results of this preliminary study indicate that levels of heavy metals and arsenic in the environment are high enough to cause adverse effects in birds. This study also highlights the importance of monitoring the exposure of wildlife to contaminants especially in protected areas as these areas are vital for their conservation.
Isolation and characterization of spiciferone A from an endophytic fungus Phoma macrostoma isolated from Artocarpus altilis fruits
(University of Peradeniya, Sri Lanka, 2016-11-05) Thanabalasingam, D.; Kumar, N.S.; Jayasinghe, L.; Fujimoto, Y.
This study focuses on the chemistry and bioactivity of secondary metabolites produced by an endophytic fungus from the fruit of Artocarpus altilis (family Moraceae). A. altilis, commonly known as “Del” in Sri Lanka. Its fruits are known as breadfruit and cooked as a starchy staple food. Various parts of A. altilis are used to cure many diseases. An endophytic fungus isolated from the fruits of A. altilis was identified as Phoma macrostoma by molecular means. Pure culture of P. macrostoma was inoculated into twenty 1 L- Erlenmeyer flasks, each containing 400 mL potato dextrose broth media, allowed to incubate at room temperature for 10 days and shaken every other day for another 18 days. After four weeks the culture broth and mycelia were extracted with EtOAc separately. The mycelia were further extracted with MeOH. Concentration of the extracts under reduced pressure using a rotary evaporator gave two EtOAc extracts and a MeOH extract. The two EtOAc extracts were combined due to the close similarity of the TLC pattern. Bioassay screening indicated that the combined EtOAc extract was active in brine shrimp lethality assay (IC₅₀ 78 ppm), exhibited DPPH radical scavenging activity (IC₅₀ 738 ppm) and had phytotoxic activity inhibiting root (IC₅₀ 906 ppm) and shoot (IC₅₀ 558 ppm) growth. The MeOH extract was active in DPPH radical scavenging assay (IC₅₀ 508 ppm). Chromatographic separation of the EtOAc extract furnished spiciferone A (1), which was identified by detailed analysis of NMR data. Spiciferone A (1) is a polyketide-derived fungal metabolite with a bicyclic unit comprised of a fully subsituted γ–pyrone and a cyclohexenone and reported as a plant growth inhibitor. Ths is the first report of the isolation of P. macrostoma as an endophyte from the fruit of A. altilis and the isolation of 1 as a secondary metabolite from P. macrostoma.
Histological parameters and expression of EGFR and β – catenin in oral squamous cell carcinoma; A preliminary study
(University of Peradeniya, Sri Lanka, 2016-11-05) Karunatilaka, H.D.N.U.; Siriwardena, B.S.M.S.; Tilakaratne, W.M.
The incidence of oral squamous cell carcinoma (OSCC) remains high and it is ranked as the 6th commonest cancer globally. Although the presence of neck lymph node metastases at the diagnosis can decrease the 5-year survival rates to lower than 50%, treatment of the clinically-negative neck is still controversial. Invasive front of the cancer is known to be important in predicting metastasis and prognosis thus the use of molecular markers together with traditional histological methods may improve the strategy for comprehensive management of patients with OSCC. This study is aimed to analyse the expression of Epithelial Growth Factor Receptor (EGFR) and β – Catenin molecules with histological parameters and demographic data. A total of 39 OSCC cases treated with excision and neck dissection at Oral Maxillofacial units in Sri Lanka were assessed for pattern of invasion, tumour stage, level of differentiation, expression of EGFR and β – Catenin. Demographic data was obtained from Oral Pathology database and histological materials were collected from the archives in the same Department. Data were analysed using SPSS version 16. A statistically significant expression of EGFR was observed with pattern of invasion (p<0.05). As the sample size was small, a significant/reliable relationship could not be established with metastasis for the same. Overall β – Catenin expression was low in cancer cases and showed no significant association with pattern of invasion or metastasis. A significant positive relationship between the pattern of invasion and metastasis (p<0.05); and between the host response and survival rate (p<0.05) were observed. EGFR is a reliable candidate molecule to be used in combination with histological parameters to predict prognosis of OSCC. As this is a preliminary study which however used a panel of different molecules to assess the advancing front of the cancer, a larger sample needs to be tested to draw safe conclusions before making recommendations for the clinicians.
Fractures of acrylic dentures: An analysis of patterns and associated factors
(University of Peradeniya, Sri Lanka, 2016-11-05) Thilakumara, I.P.; Rasnayaka, R.M.S.G.K.; Jayasinghe, J.A.V.P.; Jayasinghe, R.M.
Acrylic resin (polymethylmethacrylate) is the material of choice in fabrication of complete denture bases and it is also commonly used for removable partial dentures especially in developing countries such as Sri Lanka due to economic reasons. Due to the low strength of the acrylic resin material, one of the commonest denture complaints is fracture of acrylic dentures. Therefore, this study aims to explore the pattern and associated factors of complete and partial acrylic denture fractures. In this cross sectional pilot study, 110 removable acrylic denture wearers complaining of denture fractures were selected. An interviewer-administered questionnaire was used to collect data on types and causes of denture fractures and their associated factors. The denture examination and intraoral examination were carried out. The findings were statistically analyzed. Out of the dentures that were examined, 39% were complete dentures and 61% were partial dentures. The most commonly (34%) fractured dentures were upper partial dentures. The commonest type of fracture was fracture of the denture base. When considering all the dentures, 51% of the fractures occurred during mastication. A significant correlation was found between the denture fractures and the age of the denture. Midline was the commonest fracture site in complete dentures. With the findings of this pilot study, it is presumed that the most commonly fractured dentures are upper partial dentures and a majority of denture fractures are caused during mastication. There was a statistically significant correlation between denture fractures and denture age. However, analysis of a larger sample is needed to arrive at conclusions regarding denture fractures and their associated factors.
Retrospective analysis of demographic findings and concordance between clinical and histopathological diagnosis of radicular cysts
(University of Peradeniya, Sri Lanka, 2016-11-05) Jayasooriya, P.R.; Eden, P.; Tennakoon, T.M.P.B.
Radicular cyst is an odontogenic cyst of inflammatory origin that occurs in relation to non-vital teeth. Large radicular cysts associated with non-restorable teeth are generally enucleated. Although, clinical and radiological findings are adequate to provide a provisional diagnosis of radicular cyst, submission of enucleated specimens for histopathological confirmation is mandatory to rule out other pathologic processes. The aims of this retrospective study were to present the demographic findings namely, age, gender and site distribution of radicular cysts and to present the level of agreement between clinical and histopathological diagnoses achieved for radicular cysts. Four hundred and eleven cases of histopathologically confirmed radicular cysts, diagnosed during a period of 5years from 2011 to 2015 were available for the analysis. In addition, further eighty cases with the clinical diagnosis of radicular cysts that were histopathologically diagnosed as different pathologic entities were used to assess the level of agreement between clinical and histopathological diagnoses. Out of the 411 radicular cysts, 2.4% (10) lesions occurred in the deciduous dentition, while a majority (97.6%) of lesions affected the permanent dentition. The majority (73.2%) of radicular cysts occurred in adults between 21-60 years, while 10.9% (45) and 10% (41) occurred in children and elderly patient respectively. Male predilection with male to female ratio of 1.5:1 was observed. Interestingly the majority (83.7%) of radicular cysts had occurred in the maxilla compared to 16.7% (67) in the mandible. Out of the 411 histopathologically confirmed radicular cysts, 342 had been correctly diagnosed clinically, achieving a rate of agreement of 83.2%. Out of the 422 with a clinical diagnosis of radicular cysts, only 81.1% were confirmed histopathologically. Of the remaining 80 lesions with a clinical diagnosis of radicular cyst 2 lesions were diagnosed as malignancies, 39 as odontogenic tumours, 27 as odontogenic and non-odontogenic cysts of developmental origin and 6 as periapical abscesses. In conclusion, although good agreement is observed between clinical and histopathological diagnosis of radicular cyst, it is mandatory to histopathologically confirm the diagnosis of radicular cyst, as approximately one fifth of the clinically diagnosed radicular cysts may in fact be tumours or malignancies that require different management strategies.
A series of isocoumarins from an endophytic fungus Biscogniauxia capnodes from Phyllanthus acidus
(University of Peradeniya, Sri Lanka, 2016-11-05) Dissanayake, D.M.; Kumar, N.S.; Jayasinghe, L.; Fujimoto, Y.
Microbial natural products play major role in applications in agriculture, medicine, cosmetics and food industry. Fungi are living eukaryotic organisms and can be categorized into epiphytic fungi and endophytic fungi. Endophytic fungi reside in internal plant tissues of higher plants whilst epiphytic fungi grow on the surface of plants. As a continuation of our studies on chemistry and bioactivity of fungi associated with edible fruits of Sri Lanka, secondary metabolites produced by an endophytic fungus isolated from popular edible Phyllanthus acidus fruits was studied. Phyllanthus acidus (goose berry) is a tree of family Phyllanthaceae. An endophytic fungus Biscogniauxia capnodes was isolated from the fruits of P. acidus, and identified by molecular means. Pure cultures of B. capnodes were inoculated into potato dextrose broth (PDB) media, allowed to stand for a week and then incubated at room temperature for another two weeks while shaking every other day on a laboratory shaker. The culture broth and mycelium were separately extracted with EtOAc and the residual mycelium was further extracted with MeOH. According to the similar TLC analysis, the two EtOAc extracts were combined. The EtOAc and MeOH extracts were subjected to bioassays for antioxidant activity (against DPPH radical scavenging), phytotoxicity against lettuce (Lactuca sativa) seed germination inhibition and antifungal activity (against Cladosporium cladosporioides). The EtOAc extract showed positive response in antifungal, antioxidant and phytotoxicity bioassays. Chromatographic separation of EtOAc extract furnished seven compounds. These compounds were identified as six isocoumarins, 8-hydroxy-3,5-dimethylisochroman-1-one (1), 8-methoxy-3,5-dimethylisochroman-1-one (2), 7,8-dihydroxy-3,5-dimethylisochroman-1-one(3), 6-methoxy-8-hydroxy-3-methyl-1H-isochromen-1-one (4), 8-hydroxy-6,7-dimethoxy- 3-methyl-1H-isochromen-1-one (5), 6,8-dihydroxy-7-methoxy-3-methyl-1H-isochromen-1-one (6), 5-methylbenzene-1,3-diol (7), by detail analysis of ¹ H & ¹³C NMR data and comparison with reported data. This is the first report of isolation of an endophytic fungus Biscogniauxia capnodes from the fruits of P. acidus as well as isolation of isocoumarins as metabolites from the fungus B. capnodes.
Synthesis, characterization and investigation of antimicrobial activity of monomeric ni(ii) and co(ii) complexes of a schiff-base ligand synthesized from 2, 4-dinitrophenylhydrazine and acetyl acetone
(University of Peradeniya, Sri Lanka, 2016-11-05) De Silva, P.I.T.; Ganehenege, M.Y.U.
The chemistry of Schiff-base transition metal complexes has attracted the interest of both inorganic and bioinorganic chemists in recent years mainly due to their catalytic and microbiological activities. Therefore, the present study was focused on the antimicrobial activity of a Schiff-base ligand (L) and its Ni(II) and Co(II) complexes as the chemistry of these metal complexes can be monitored easily using spectroscopic techniques. L was prepared by refluxing ethanolic solutions of 2, 4-dinitrophenylhydrazine and acetyl acetone in 2:1 molar ratio. Ni(II) and Co(II) complexes were synthesized according to the template synthesis method. All the complexes were characterized by FTIR, H¹-NMR and UV-Vis spectroscopic techniques. According to the FTIR spectra, both bands at 1635 cm⁻¹ and 3441 cm⁻¹ corresponding to the C=N imine and N-H vibrations respectively, have shifted to lower frequency (1330-1615 cm⁻¹) due to the complex formation. Metal-L bond formation is confirmed due to the presence of a band around 530-550 cm⁻¹ corresponding to the ν (M–N) vibrational mode. The UV-Visible spectra of L exhibits intense absorption peaks at 217 and 345 nm. L incorporation to the metal is evident due to the presence of highly intense bands around 215-300 nm and 305-360 nm in both Co(II) and Ni(II) complexes. The main peaks of ¹ H NMR of L and the Ni(II) complex in CDCl₃ are similar; the aromatic, CH₃, CH₂ and N-H protons appear in the range 7.2-8.9, 2.1-2.2, 3.3 and 4.0 ppm, respectively. Antibacterial activity of the synthesized L and the complexes were determined using thin-layer chromatography with direct bioautography for Escherichia coli sp. Antifungal activity was studied using well diffusion method for Cladosporium sp. According to the results, both free ligand and its Co(II) and Ni(II) complexes show antibacterial activity. Antibacterial activity of metal complexes is higher than that of the free ligand. In contrast, antifungal activity was higher for the free ligand than the metal complexes. Overall results of this study reveal that the L, Ni(II) and Co(II) complexes can be used as antifungal and antibacterial agents.
In vitro release study of Linamarin encapsulated Chitosan nanoparticles
(University of Peradeniya, Sri Lanka, 2016-11-05) Nicholas, I.H.V.; Karunaratne, V.; Amaratunga, G.A.J.; Karunaratne, D.N.
Linamarin, a cyanogenic glycoside has exhibited the potential as a drug candidate for cancer treatment. Nano-based delivery system will be a suitable application for selective and safe delivery of linamarin. Chitosan (CS) nanoparticles have gained more attention as effective drug carriers in cancer chemotherapy because of their better stability, biocompatibility and for possessing versatile routes of administration. This study focused on the fabrication, physicochemical characterisation and controlled release properties of linamarin encapsulated CS NPs. Linamarin loaded nanoparticles were prepared by incorporating linamarin into CS solution followed by drop wise addition of the TPP. The selected mass ratio of CS: TPP was 6:1. The particle size and zeta potential value were 49±2 nm and 52±3 mV, respectively. Entrapment efficiency of 85 ± 6 % was achieved with a weight ratio of 150:1 (CS: linamarin). Nanoparticles were characterised using FT-IR, thermo gravimetric analysis (TGA), TEM and SEM techniques. The shape of NPs particles was approximately spherical according to SEM and TEM analysis. FT-IR results suggested cross-linking and interactions between linamarin and CS as well as CS and TPP. TGA analysis also proved the incorporation of linamarin into CS nanoparticles. In vitro release characteristics of linamarin from CS NPs were investigated in buffer solutions with pH 2 (KCl-HCl) and 7.4 (phosphate buffer saline).Release profile in both pH values appeared to have an initial rapid release followed by a controlled release behavior. Released amounts of linamarin at 120 h were 68.83% with pH 7.4 and 70.79% with pH 2. Smaller size and positive zeta potential for linamarin loaded CS nanoparticles indicate their potential for cellular uptake, long circulation and retention time inside the body. Controlled/sustained release behavior enhances the bio availability of the drug, reducing possible side effects. Therefore targeted delivery of linamarin using CS nanoparticles will be an effective, promising alternative method to other cancer treatment methods.
Genetic diversity and population structure of malaria vector mosquitoes Anopheles peditaeniatus, An. subpictus and An. vagus (Diptera: Culicidae) in five districts of Sri Lanka
(University of Peradeniya, Sri Lanka, 2016-11-05) Weeraratne, T.C.; Surendran, S.N.; Karunaratne, S.H.P.P.
Anopheles subpictus is the secondary vector and An. peditaeniatus and An. vagus are potential vectors of malaria in Sri Lanka. Understanding population structure of vectors is vital in implementing successful vector control programmes to face the threat of re-emergence of malaria in Sri Lanka. This study reports the genetic diversity and the population structure of An. peditaeniatus, An. subpictus and An. vagus in five geographical locations in Sri Lanka using their mitochondrial gene, Cytochrome oxidase subunit I (COI). Adults were collected from Ampara, Badulla, Batticoloa, Jaffna and Kurunegala districts and the COI sequences were obtained from morphologically identified species using Polymerase Chain Reaction (PCR) assay. Statistical analyses were conducted using Dnasp 5.10.01 and Arlequin 3.11. An. peditaeniatus, An. subpictus and An. vagus had 8, 15 and 10 haplotypes respectively. All the three species had high genetic diversities. An. subpictus had the highest nucleotide diversity (0.025 ± 0.011) while An. peditaeniatus had the lowest (0.007 ± 0.002). According to neutrality tests, there is no positive selection driven in any of these species. No significant pairwise differences or genetic structure variations among An. peditaenatus or An. vagus populations which shows that random mating occurs among different populations of each species. A significant pairwise difference was observed between Jaffna (northern province) and Kurunegala (northwestern province) An. subpictus populations (FST= 0.965,). This strongly supports the previous reports on the presence of two different sibling species of An. subpictus in these two provinces. Analysis of Molecular Variance (AMOVA) results showed 82.21% significant genetic structure variation between An. subpictus populations (FCT= 0.822) compared to a smaller 17.79% variation within populations (FSC= 1.000), suggesting the existence of different An. subpictus sibling species in different geographical areas. The present study shows that geographic distance between populations has no effect on the population structures of An. peditaeniatus and An. vagus but affects the population structure of An. subpictus. Application of control measures against An. subpictus must be done with close monitoring since similar control measures may not be effective for all the populations and the high genetic variation can give rise to the population’s resistant to control measures.
Determination of optimum nitrate and phosphate concentrations for maximum growth of Chlorella Sp.
(University of Peradeniya, Sri Lanka, 2016-11-05) Herath, H.M.C.H.; Ganehenege, M.Y.U.
Algae biomass can be used for various purposes such as biofuel production, extraction of high value added food and pharmaceutical products. While growing algae for such purposes, removal of nitrogen and phosphorous from waste water polluted from nitrogen and phosphorous sources also can be achieved by growing algae. To obtain maximum algae growth, both physical and chemical parameters can be optimized. Controlling physical parameters are quite expensive rather than controlling chemical parameters such as nutrients and pH of the medium. Therefore, outdoor conditions with different nutrient contents were used. Nitrogen, phosphorus and potassium are the most significant macronutrients for algal growth. In this research, inorganic phosphate (PO₄³⁻) and inorganic nitrate (NO₃⁻) were used as the nitrogen and phosphorus sources, respectively, in order to find the best NO₃⁻: PO₄³⁻ concentration and the best N: P atomic ratio for the maximum Chlorella sp. growth. The growth measurement of cell density was taken using UV-Visible Spectroscopy and specific growth rate (μ) was calculated. According to previous research, N: P atomic ratio is the most significant factor for algae growth where N: P = 16:1 for the maximum growth. However according to our results, not only the N: P atomic ratio, but also NO₃⁻ and PO₄³⁻ concentrations were equally important for algal growth. Under the experimental conditions, the maximum specific growth rate (μmax) was observed when the concentrations of NO₃⁻ and PO₄³⁻ were kept at 200 ppm and 10 ppm respectively, where N: P atomic ratio was 14: 1. However, under the same N: P ratio (14:1) at different NO₃⁻ : PO₄³⁻ concentrations (when NO₃⁻ > 200 ppm and PO₄³⁻ > 10 ppm) the maximum growth was not observed. The pH of the medium also increased significantly with the growth of algae. This study demonstrated that optimum nutrient conditions maximize the algae growth under outdoor conditions and their nutrient removal capability can be used for waste water treatment.
Host preferences of frog-biting Uranotaenia mosquitoes in Sri Lanka
(University of Peradeniya, Sri Lanka, 2016-11-05) Herath, B.P.; Ekanayake, C.; Karunaratne, S.H.P.P.; Bernal, X.E.; De Silva, W.A.P.P.
Hematophagous insects often have particular host preferences to maximize their foraging efficiency that result in close ecological associations with their victims. Identification of host preference of blood feeding mosquitoes is vital to understand how disease causing pathogens transmit among wild- animals and from wild-animals to humans. The objective of the present study was to uncover the host preferences of frog-biting mosquitoes in Sri Lanka. Feeding behaviour of frog-biting mosquitoes and calling activities of anurans (ground dwelling Duttaphrynus melanostictus, arboreal Polypedates cruciger and Pseudophilautus rus) were examined once a week from April 1ˢᵗ to June 30ᵗʰ 2016 at a home garden in Ranawana, Katugastota. Mosquitoes attracted to frog calls were collected at hourly intervals from 19.00 to midnight. Sound traps were also used to collect mosquitoes that responded to D. melanostictus calls. Collected mosquitoes belonged to the genus Uranotaenia and were identified as three morphotypes (Ur. sp1, Ur. sp2 and Ur. sp3). These Uranotaenia morphotypes had different host preferences towards anurans at the study site and shared temporal and spatial niche partitioning with their preferred host anurans. The highly abundant Uranotaenia sp1 (n=1271) was often found at ground level, and mostly attracted towards ground dwelling D. melanostictus (98.1%). The sound trap (n=5 traps) with D. melanostictus calls at natural intensities also attracted 100% Ur. sp1 (n=45) supporting the species specific interactions between them. Moderately abundant Uranotaenia sp2 (n=441) often inhabited an average height of 0.7 ± 0.1m, and mostly bite P. rus (98.6%) that was abundant at 0.7 ± 0.1m. The least abundant Ur. sp3 (n=42) was often found at an average height of 1.4m and was attracted to P. cruciger (97.6%). Peak activity hours of Ur. sp1 (22.00-23.00 hrs), Ur. sp2 (19.00-20.00 hrs) and Ur.sp3 (20.00-21.00 hrs) overlapped with active peak hours of D. melanostictus, P. rus and P. cruciger respectively. Our results revealed high species- specificity between the mosquitoes and their anuran host highlighting host niche partitioning in a relatively simple community for the first time in Sri Lanka. Future studies will explore the factors that influence the evolution of species-specific interactions between mosquitoes and anurans in Sri Lanka.
Heavy metal biosorption by Alginic acid extracted from Sargassum sp.
(University of Peradeniya, Sri Lanka, 2016-11-05) Dhanukshi, H.G.N.; Cooray, A.T.; Ratnaweera, D.R.; Kuruwita-Mudiyanselage, T.D.
Water is the driving force for many natural processes on the earth. It is essential to protect the quality of water for the survival of all living beings. However, water pollution has increased significantly during the last few decades with the rapid industrialization processes. This work highlights a development of a low cost, sustainable and efficient water purification sorbent extracted from a seaweed species grown in the coastal areas of in Sri Lanka. Alginic acid extracted from Sargassum sp. collected at the coast of Beruwela has been studied extensively as a candidate material to remove metal ions from natural and waste waters. The extracted alginic acid was characterized using FTIR spectroscopy. Metal absorption capacity, selectivity and the extent of reusability of alginic acid were determined for the metal ions ( Pb²⁺, Cu²⁺, Zn²⁺, Co²⁺, Ca²⁺, and Mg²⁺ ) by using respective metal ion solutions. Alginic acid has shown maximum adsorption towards Pb²⁺ ions with 488.5 mg/g capacity. Adsorption capacity for metal ions Cu²⁺, Zn²⁺, Co²⁺, Mg²⁺ and Ca²⁺ ions were 314.4 mg/g, 287.4 mg/g, 283.8 mg/g, 83.6 mg/g and 74.4 mg/g respectively. It showed more selectivity towards Pb²⁺ ions over the other ions in a metal ion solution. Reusability of the aliginic acid for two adsorption-desorption cycles were experimented and determined that the metal ion removal capacity remains fairly constant. Furthermore, alginic acid showed an ability to remove Pb²⁺ ions completely from Pb²⁺ spike natural water sample, which initially contained 5.0 mg/L Pb²⁺ ion concentration. Ca²⁺ and Mg²⁺ ions removal capacities of alginic acid from natural water system were 57.5 mg/g and 36.6 mg/g respectively. It can be concluded that alginic acid is an economical, sustainable remedy for water purification in Sri Lanka to remove heavy metal ions from waste water.
Electropolymerization of partially purified natural terthiophenes extracted from roots of Tagetes erecta
(University of Peradeniya, Sri Lanka, 2016-11-05) Kaluarachchi, C.P.; Ratnaweera, D.R.; Prashantha, M.A.B.
To fulfill the growing global energy demand, harvesting energy directly from the sunlight, using solar cells, is considered as one of the best methods available. Conjugated polymers have significant influence in changing the perception of solar cell materials due to low cost and manufacturing simplicity compared to conventional Si-based solar cells. It has been shown that the inorganic polymers can be replaced by organic conjugated polymers to construct the organic solar cells. Polythiophene with both doped and undoped states, are one of the major categories of conjugated polymers used in organic solar cell applications. Starting materials of polythiophenes are commonly obtained from nonrenewable sources such as petroleum byproducts and their price may vary with the crude oil price. Green thiophene derivatives are reported in roots of Tagetes sp. The current study discusses electropolymerization of polythiophenes from hexane soluble fraction (HSF) of partially purified roots extract of thiophene derivatives from the Tagetes erecta. In literature, several thiophene derivatives were identified in the root extracts of Tagetes erecta including 5-(3-buten-1-ynyl)-2,2-bithienyl, 5-(4-hydroxy-1-butynyl)-2,2- bithienyl, 5-(4-acetoxy-1-butynyl)-2,2-bithienyl and 2,2:5,2-terthienyl (terthiophene). In this work, crude extract of Tagetes erecta was partially purified and partitioned into hexane. Partitioning of thiophene derivatives into hexane was confirmed by GCMS studies. According to GCMS data, terthiophene is the only possible compound in HSF that can undergo electropolymerization. Cyclic voltammetric study was carried out to characterize the redox potential of terthiophenes in HSF and oxidation of terthiophenes was observed at 1.05 V. Electropolymerization of terthiophenes was carried out in acetonitrile medium under inert environment and LiClO₄ was used as the electrolyte. During the electropolymerization, a thin layer was formed on the anode surface. Electropolymerized products from HSF were characterized using FTIR, UV-Visible Spectroscopy and powder X-ray diffraction techniques and those were compared with the results of the electropolymerized product of pure thiophene monomers. These results further confirmed the possibility of electropolymerization of terthiophenes from the HSF of Tagetes erecta, to obtain highly crystalline polythiophenes.
Use of acrylamide based hydrogels for pre-concentration of trace level chromium ions
(University of Peradeniya, Sri Lanka, 2016-11-05) Kulasekara, D.N.; Chinthaka, S.D.M.
The determination of trace level (ppb) metal ions by low sensitive flame atomic absorption spectroscopy (FAAS) requires sample pre-concentration procedures. In this study, Poly (acrylamide-co-maleic acid) hydrogel (PAMMA) was prepared by free radical polymerization in the presence of cross linking agent (N,N’-methylenebisacrylamide), initiator (ammonium persulphate) and accelerator (N,N,N,N-tetramethylethylenediamine) to study the pre-concentration potential of chromium ions. The swelling behavior and adsorption capacities were studied at various maleic acid levels at different pH values. The prepared hydrogels showed good swelling behavior that was highly dependent on the pH of the medium. The maximum swelling ratio of 108 was observed at pH = 7. The affinity of trivalent chromium (Cr³⁺) and hexavalent chromium (CrO₄²⁻) for PAMMA hydrogels were studied at pH 4 where hydrogels were partially deprotonated. The results indicated that affinity of trivalent chromium was significantly higher than that for hexavalent chromium ions. Therefore poly (acrylamide-co-maleic acid) hydrogel was selected to pre-concentrate trivalent chromium. The critical factors such as pH, ionic strength, acrylamide-maleic acid ratio and cross-linking density were also studied for the optimization of adsorption capacity of prepared hydrogels for trivalent chromium absorption. Maximum adsorption capacity was observed when the acrylamide: maleic acid molar ratio was 7:4. With the increase of crosslinking density, the adsorption capacities decreased. The adsorption capacity also dropped with ionic strength. It was found that the absorption capacity dropped from 42.3 to 26.3 mg g⁻¹ when ionic strength was increased from 0.01 to 1. The optimum uptake of Cr³⁺ was found to be at pH 5 and the equilibrium contact time was reached at around 4 hours. Adsorption mechanisms were studied by both Langmuir and Freundlich isotherm models at room temperature (29 ⁰C) and it was found that the adsorption behavior was better explained by Freundlich isotherm. The kinetic studies of trivalent chromium indicated that the rate of adsorption followed pseudo second-order kinetics at room temperature. Pre-concentration factors of Cr³⁺ at optimum conditions in different initial concentrations were studied at non-competitive conditions. Very good linear correlation of the prepared trivalent chromium solutions at ppb levels and the pre-concentrated solutions was found. The linear correlation co-efficient (r²) of 0.998 indicates that poly (acrylamide-co- maleic acid) hydrogel can be used to pre-concentrate trivalent chromium in the range of 40 -70 ppb into 2-10 ppm range.

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