Chemistry

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    Medicinal plants commonly used against cancer in traditional medicine formulae in Sri Lanka.
    (Saudi Pharmaceutical Journal, 2019) Kuruppu, A. I.; Paranagama, P.; Goonasekara, C. L.
    Cancer is a global burden. In low- and middle-income countries around 70% of deaths are due to cancer. For a number of years natural products have been a good source of agents for combatting cancer and plants have played a huge role in anti-cancer product development. For many centuries, indigenous cultures around the world have used traditional herbal medicine to treat a myriad of diseases including cancer. In Sri Lanka, a number of plants have been reported to have anti-cancer properties and some of the commonly used plants are described in this review with an account of their compounds and modes of action. Only a small number of the plants in Sri Lanka have been tested for their bioactivity and more research is required to determine their medicinal activity with the aim of developing novel drugs to fight this disease.
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    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.
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    Computational investigation of pesticide induced oxidative stress and its impact on the Chronic Kidney Disease of unknown etiology (CKDu)
    (International Journal of Science, Environment and Technology, 2019) Pandithavidana, D. R.; Deshan, T. M. V.
    The chronic kidney disease of unknown etiology (CKDu) has been a major health issue in Sri Lanka within the last three decades. Many investigative efforts have been carried out to identify its unknown origin and several risk factors which have been associated. A possible link between oxidative stress and the progression of the disease has been identified. The environmental factors which favor the development of oxidative stress are prevalent in those affected areas. The study of “pesticide induced oxidative stress” has been a topic of research interest. Alterations in the balance between the production of free radicals and the antioxidant defenses were recognized as one of the main causes. Four major pesticides were docked with different enzymes which directly related to mechanisms in generating oxidative stress, using Auto Dock molecular docking program. The strength of the binding of the pesticide in the binding site of the corresponding enzyme was used to emphasize its potential interaction with Cytochrome P450 A34enzyme. According to molecular docking investigations, it was evident that three organophospahates; Profenofos, Diazinon and Chlrofyrifos possessed relatively similar binding energies at the active site compared to the inducer for Cytochrome P450 A34 enzyme. These organophosphates behave as the potent enzyme inducers as well as substrates which involved in bio-activation. The computational findings directed to disclose how reactive oxygen species were generated to cause oxidative stress and it can be utilized to predict mechanistic steps related to the pesticide induced oxidative stress.
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    Molecular docking studies to identify secondary metabolites present in Ashwagandharishta and their effectiveness towards memory related disorders
    (Global Journal of Engineering Science and Research Management, 2019) Pandithavidana, D. R.; Munaweera, R. K. W.
    Ashwagandharishta is a famous Ayurveda medicine (in Asian countries) that is used to treat psychiatric conditions, dullness, memory related diseases, anxiety, schizophrenia sluggishness, epilepsy, depression and etc. Memory defects are closely allied with imperfect cholinergic neurotransmission. Repairing mechanisms for theses impaired processes afford promising treatment strategies for these kinds of disorders. Alpha-7 nicotinic acetylcholine receptor is a sub type of nicotinic acetylcholine receptor which has been recognized as one of the most useful drug target for the treatment of nervous system associated disorders. Molecular docking analyses have been carried out to detect any possible secondary metabolites present in Ashwagandharishta that could act as agonists of alpha-7 nicotinic acetylcholine receptor. According these computational findings, it has been found that two phytochemicals; anaferine and anahygrine exhibit promising agonistic activity towards the receptor. Thus anaferine and anahygrine have high possibility to serve as alpha-7nAChR agonists which demonstrate potential drug action towards memory related disorders.
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    Computational Investigation of Structural, Electronic and Thermodynamic Properties of Nonylphenolethoxylate Surfactants
    (International Journal of Science, Environment and Technology, 2019) Pandithavidana, D. R.; Jayalath, W. I. M.
    Nonylphenol ethoxylates (NPEs) are group of non-ionic surfactants commonly known as Tergitol NP surfactants. The hydrophilic-lipophilic-balance (HLB value) is used as the key parameter by surfactant formulators to study the properties of non-ionic surfactants. Even though the HLB values of two surfactants are equal or close enough to each other, the expected properties cannot be obtained by replacing one surfactant with another one. This issue leads to a necessity to carry out many trial and error tests to identify the equivalent surfactants in industrial applications. The strong hydrogen bonding with water, Gibbs free energy change of solvation (ΔGsolv), molecular dipole moment and maximum absorption wavelength (λmax) have been developed as key performance indicators of a better surfactant in this research work. Computed results predict that NPEs are well stabilized in the aqueous medium with the extension of ethoxylate chain length, illustrating a linear relationship of ΔGsolv with respect to the number of ethylene oxide units. This evidence has been further supported by the decrease in hydrogen bond length, between the NPEs and water molecules with the extension of the ethoxylate chain of the surfactant. Among ortho- , meta-, and parasubstituted NPEs, due to the presence of higher dipole moments of meta-substituted NPEs indicated that they form more efficient secondary interactions in aqueous medium. Moreover meta-substituted NPEs demonstrate relatively higher thermodynamic stability (than ortho- and para- substituted NPEs) due to the presence the highest HOMO-LUMO gap.
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    A NEW ANTIOXIDANT ACTIVE COMPOUND FROM THE ENDOLICHENIC FUNGUS, PENICILLIUM CITRINUM INHABITING THE LICHEN, PARMOTREMA SP
    (International Journal of Pharmaceutical Sciences and Research, 2019) Wickramarachchi, S.A.; Samanthi, U.; Wijeratne, K.; Paranagama, P.A.
    Context: Endolichenic fungi are the microorganisms living inside the thalli of the lichen and found to be a new source of bioactive secondary metabolites. This is an underutilized source of bioactive compounds and has not been studied extensively. Genus, Parmotrema is one of the foliose lichens with largely rounded lobes and occurs on rocks of rain forests, sub-montane and montane forests in Sri Lanka. Aims: The endolichenic fungi available in Sri Lanka and the chemistry of their secondary metabolites have not been explored thoroughly. This study aims at exploring novel bioactive compounds available in Penicillium citrinum inhabiting Parmotrema sp. Methods and Material: The lichen, Parmotrema sp., was collected from Hakgala Botanical Garden in Sri Lanka and its fungal strains were isolated and identified by Genomic DNA sequencing. Compounds were first extracted to ethyl acetate and subsequently subjected to bioassay-guided fractionation to isolate the bioactive compounds. The DPPH assay was used to determine the antioxidant activity. The active compound/s was separated by column chromatography, and its structure was elucidated by IR, 1D and 2D-NMR, 13C-NMR and MS. Statistical Analysis Used: The IC50 of the crude extract was calculated using Probit analysis (MINITAB® Release 14.1. Minitab Inc. 2003 Statistical Software). Results: A bioactive compound, named PP-PC-03 together with PP-PC-01 and PP-PC-02 was isolated from P. citrinum. All three compounds showed antioxidant activity in the DPPH assay with IC50 values 159.6 ± 22.3, 120.1 ± 11.7 and 68.6 ± 4.3 μg/mL respectively. Conclusion: Based on spectral analysis the structure of PP-PC-03was determined as 10-Ethylidene-2,4,9-trimethoxy-10,10a-dihydro-7,11-dioxa-benzo[b] heptalene-6,12-dione and identified as a new compound. Comparatively PP-PC-02 and PP-PC-03 had moderate antioxidant activities while PP-PC-01 showed strong radical scavenging activity.
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    ZnS Assisted ZN Doping in CdZnS Electrodeposition
    (Journal of Science 2019, Department of Chemistry, University of Kelaniya, Sri Lanka, 2019) Sarathchandra, K. A. D. M. S.; De Silva, D. S. M.; Pathiratne, K. A. S.
    Many reports have been published elsewhere on making thin films of cadmium zinc sulphide (CdZnS) using different techniques. This article summarizes a method developed to form CdZnS by incorporating electrodeposited Cd and S atoms simultaneously to the chemically formed ZnS material in the electrolytic bath at the conducting surface of fluorine doped tin oxide (FTO) coated glass substrate. Moreover, the mechanism of formation of CdZnS is proposed as a solid state reaction between electrodeposited Cd and S atoms on the glass/FTO substrate with adsorbed ZnS particles from the electrolytic bath. The precursors used for Cd, S and ZnS in the electrolyte were aqueous solutions of CdCl2, ZnCl2 and Na2S2O3. Two different methods were tested to form ZnS within the electrolyte bath where one forming ZnS in the bath at the beginning of electrodeposition of Cd and S and in the other one, ZnS is formed before the electrodeposition of Cd and S. The results of the band gap measurements show an undulation which is closer to the band gap energy of CdS indicating probable codeposition of one or more materials such as CdS, (2.42 eV), ZnS (3.7 eV), CdO (2.2 eV), and ZnO (3.2 eV) along with CdZnS. The Tauc plot resulted by the material produced in method 1 has shown an undulation at the onset of Tauc plot which is near the band gap energy of CdS indicating the codeposition of CdS with CdZnS, but the Tauc plot of CdZnS electrodeposited from method 2 has shown clear separation in band gaps from 2.44 – 2.52 eV, when the annealing temperature, the Zn2+ ion concentration in bath and the electrodeposition pH were varied. These thin films were also characterized by photoelectrochemical (PEC) cell analysis, x-ray diffraction (XRD), energy dispersive x-ray analysis (EDXA) and scanning electron microscopy (SEM) techniques.
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    Occurrence of organic pollutants: pahs in water bodies around kelanitissa and kerawalapitiya power plants in Sri Lanka
    (Journal of Science 2019, Department of Chemistry, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Chandrasiri, H.M.H.B.; Doole, F.T.; Subramanium, S.S.
    Polycyclic aromatic hydrocarbons (PAHs) are a group of organic compounds with more than one benzene ring formed due to natural processes such as forest fires and anthropogenic activities. These ubiquitous contaminants have gathered an interest due to their toxicity and carcinogenic activity. Exposure to PAHs has also been linked with cancer, cardiovascular disease and poor fetal development. PAHs are considered as persistent organic pollutants because of their stable chemical structure and inherent resistance to decomposition. In this study, the water bodies near two diesel fueled power plants in Sri Lanka i.e., Kerawalapitiya and Kelanitissa were selected to determine the presence of PAHs in surface water and its sediment. In the preliminary sampling rounds, the presence of PAHs were identified. With increased sample size, three sampling rounds were carried out. In addition to water and sediment from Hamilton canal and Sebastian canal, water samples from wells near both power plants were analyzed. PAHs in water samples were extracted to dichloromethane and analyzed by HPLC with UV-DAD (254 nm) and HPLC- FLD (excitation at 250 nm, emission at 410 nm). Sediment samples were pretreated before the analysis and then, PAHs were extracted to methanol by ultrasonication. The presence of low, medium and high molecular weight PAHs in water and sediment samples obtained from both sites were detected. Total concentration of PAHs in surface water samples obtained from Sebastian canal during rainy season (April 2015), dry season (July 2015) and rainy season (June 2016) were 0.11-1.71 μg/L, 2.36-14.68 μg/L and 6.88 μg/L - 10.05 μg/L, respectively. Furthermore, PAH content in water samples obtained from Hamilton canal during rainy season (April 2015), dry season (July 2015) and rainy season (April 2016) were 0.16-2.74 μg/L, 11.06- 54.89 μg/L and 5.35 - 7.79 μg/L, respectively. Well water samples obtained from Kelanitissa (W1) and Kerawalapitiya (W3) showed the presence of high amounts of BaP (0.025 μg/L) and BkF (0.339 μg/L) respectively which are higher than the guideline values for BaP (0.01 μg/L) and BkF (0.1 μg/L) according to European Unions’ drinking water standards. The total PAH amount in surface water in both sites were higher in dry season than that of in rainy season. This may due to accumulation of PAHs over the time in water bodies around diesel fueled power stations during dry seasons due to lack of water flow. By investigating more dry and rainy seasons, an accumulation trend can be identified to address the seasonal variation of PAHS in water bodies.
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    Development of ZnO Thin Films for Gas Sensing Applications
    (International Research Conference (IRCUWU 2019),”Sustainable Business Transition through Technology and Innovation”, Uva Wellassa University of Badulla, Sri Lanka, 2019) Tharangika, M.O.; Atapattu, H.Y.R.; De Silva, D.S.M.
    In recent decades' gas sensing technology has become significant due to its widespread and common applications in the areas of industrial production, automotive industry, medical applications, indoor air quality supervision and environmental studies. Currently, there is an increasing interest in finding nanostructured materials to develop high performance solid-state sensors for in-house and outdoor hazardous gas monitoring. Among the available gas sensing materials, metal oxide semiconductors typically maintain a leading role owing to their high sensitivity, low cost, small dimensions and simple integration. This study, focused on developing ZnO semiconductor thin films via the technique of electrodeposition followed by a heat treatment for detecting LP (Liquid Petroleum) and H2S gases. A three electrode electrolytic cell containing of 0.1 mol ZnSO4 was used to carry out the electrodepositions. A FTO glass substrate (1x3 cm2) was used as the working electrode against an Ag/AgC1 reference electrode while using a high purity carbon rod as the counter electrode. The Zn.electrodepositions were carried out in the cathodic deposition potential (CDP) range of 0.70-1.10 V and pH range of 4.0-1.0 at a temperature of 55 °C. Subsequently, samples were heat treated at 400 °C for 1 hour in order to form ZnO thin films and samples were then characterized for their crystalline structure, surface morphology and elemental composition using the techniques of X-ray diffraction spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy respectively. The sample grown at CDP of 0.80 V at pH of 1.5 for 20 minutes was found to have average sensitivity of 6% and 38% while exposing to LP and H2S gases respectively for 2 minutes at 30 °C. Further, it revealed that, the sensitivity of the ZnO material could be enhanced by controlling the electrodeposition and the heat treatment conditions applied for the formation of ZnO nanomaterials
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    Determination of selenium content in selected edible green leaves
    (Ceylon Journal of Science, 2019) De Silva, D.S.M.; Dayarathna, A.G.S.
    The selenium (Se) contents in seven conventional Edible Green Leaves (EGL) that consumed by Sri Lankans were determined using Hydride Generation Atomic Absorption Spectrometric method (HGAAS). The EGLs that were grown in five districts under different climatic conditions in Sri Lanka were collected from Gampaha, Kandy, Kurunegala, Anuradhapura and Puttalam areas. The EGL that were subjected to current study are Centella asiatica (Sin. Gotukola), Alternanthra sessilis (Sin. Mukunuwenna), Basella alba (Sin. Nivithi/ Spinach), Boerhavia diffusa (Sin. Sarana), Ipomoea aquatica (Sin. Kankun), Amaranthus spinosus (Sin. Thampala) and Hygrophila schulli (Sin. Neeramulliya). Soil samples corresponding to each EGL sample were also collected from Gampaha, Kandy and Anuradhapura districts in order identify a relationship between the Se content in plants and soils. Prior to the analysis EGL samples and corresponding soil samples were subjected to acid digestion with nitric acid. Se contents in the EGL were in the range of 31.2 – 103.2 μg kg-1on dry weight basis. According to the results, Centella asiatica and Hygrophila schulli varieties showed relatively higher Se content, while Hygrophila schulli shown the highest value and the lowest was reported in Boerhavia diffusa. The Se content in corresponding soil samples were ranged from 96.4 to 133.9 μg kg-1on dry weight basis. The Se content in soil was higher than that in plants, but there was no significant correlation between the Se content in soil and EGLs.