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U n i v e r s i t y of P e r a d e n i y a

The Institutional Repository of the University of Peradeniya is the University's digital gateway to scholarly knowledge and research excellence. Established as the next phase of the Digital Library initiative launched by the University Library in 2011, it preserves, showcases, and provides open access to the intellectual output of the University community.

Through a rich collection of research articles, conference proceedings, theses, dissertations, and other scholarly works, the repository enhances the visibility, accessibility, and long-term preservation of knowledge, extending the global reach and impact of the University of Peradeniya’s academic and research contributions.

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Recent Submissions

Bioactivity prediction of phytochemicals against aminoglycoside resistance using QSAR modelling
(University of Peradeniya, Sri Lanka, 2023-09-20) Wijesinghe, W.R.P.; Rasangani, J.P.P.S.
Aminoglycoside (AG) resistance in bacteria is an international crisis that is estimated to have 10 million infections annually by the year 2050. With the widespread of multidrug resistance bacteria, AGs are becoming useless along with the novel drugs. Many studies have determined that the fastest route to identify treatment for AG resistance is restoring the effectiveness of existing AGs by combining them with compounds with antimicrobial properties. The main purpose of this study was to identify such compounds by predicting their bioactivity against the AG resistance in bacteria using a Quantitative Structure Activity Relationship (QSAR) model. Bioactivity data of 24 AGs and 2000 phytochemicals were retrieved from ChEMBL site. Several software was used: QSARINS; to build the model, PaDEL- Descriptor for the generation of molecular descriptors. The best QSAR model obtained using Genetic Algorithm (GA) with correlation coefficient (R2) of 0.6969 and root mean-squared error (RMSE) of 0.7795. Based on that model, the QSAR equation used to predict the pIC50 values of the phytochemicals can be given as: pIC50 =-27.7308+[50.8350*(AATS5p)] +[- 14.7553*(GATS5e)]+ [3.8896*(minssCH 2)]+[-1.5777*(maxwHBa)]. Total 14 phytochemicals had predicted bioactivity against AG resistance. They are Alpha-pinene, Miltefosine, Tilarginine, Kojic acid, Isoniazid, Gallic acid, Deacetylasperuloside,Citrifolinin B, 4-Aminobenzamidine, 2-(dodecylamino)butan-1-ol , 2-Diisopropylamino- Ethanol, 2-Diisopropylamino-Ethanol, and 1-ethyl-3-pyridin-2-ylurea. As many of them are known for their antimicrobial activity against different species, they can be considered in combining with AGs to increase the antibiotic effect. With the developed model, a large volume of phytochemicals can be screened prior to the laboratory experiments and reduce the sample number, resources, cost and time taken.
Monitoring regional differences in forest cover changes in Sri Lanka
(University of Peradeniya, Sri Lanka, 2023-09-20) Senarath, S.A.N.N.T.
Forests play a vital role in the ecosystem services provisions. There is a substantial loss in forest cover. In this context, the main objective of this study is to monitor the forest cover changes in Sri Lanka from 2001 to 2021 using remote sensing data. This forest data has been developed using the Landsat data at a 30-meter spatial resolution, which was published by Hansen et al (2013). Using JavaScript API, Those data have been analyzed through Google Earth Engine (GEE). The forest area and non-forest area of Sri Lanka were identified at the initial stage of the analysis. Subsequently, forest loss and gain which were identified from 2001 to 2021 through the transition from forest to non-forest and non-forest to forest were detected using GEE and GIS software packages. The results revealed a rapid loss in forest cover occurred during the period of postwar in the country (after 2009), driven by developmental activities in various sectors. Meanwhile, the highest forest loss was identified in 2016, which could be associated with policy changes following the establishment of a new government in 2015. The emergence of COVID-19 has slowed down deforestation during the pandemic period, the year 2019, which is connected to the decline in economic growth. According to the district-level analysis, the districts with the highest forest loss are located in the dry zone—Mullativu, Monaragala, Ampara, Polonnaruwa, Trincomalee, and Vavuniya. Those regions are widely known for their extensive utilization of agricultural land while experiencing limited growth in terms of economic development. In contrast, urban areas like Colombo, Gampaha, and Kaluthara showed low levels of forest loss as they have very little forest cover. The results highlight the urgency of protecting the forest ecosystem and the policy implementation necessity for sustainable forest management for the country.
Enhancement of cold-pressed thymoquinone extraction from black seed (Nigella sativa L.) using freeze-thaw pretreatment
(University of Peradeniya, Sri Lanka, 2023-09-20) Rajapaksha, D.S.W.; Bulathsinhala, H.S.; Madarasinghe, S.D.
Quality attributes of the black seed oil depend on various extraction methods. Conventional methods, including cold pressing, provide high quality oil but low in yield and reduced bioactive compound content. To address this, the use of innovative seed pre-treatment procedures has been investigated in order to improve oil extraction efficiency, oil yield, and bioactive compounds recovery. Thymoquinone is the main active compound extract of black seed oil which has antioxidant, anti-diabetic, anti- inflammatory, anti-cancer, anti-viral and anti-microbial properties due to its phenolic compounds. In this study, freeze-thaw pre-treatment was employed on black seeds prior to extracting oil through the cold pressing method, with the primary goal of increasing the thymoquinone content. Black seed samples were subjected to freeze at -17 °C 24 hours and thaw at 50 °C hot water bath for 1 hour and the process was repeated for 1, 2, and 3 cycles at the same temperature and times. The subsequent oil extraction was carried out using the cold-pressing technique. The study encompassed the assessment of thymoquinone content, quantification of the extract yield, and the undertaking of physical and chemical evaluations on the obtained oil. Thymoquinone content in the black seed oil was determined using UV-Visible spectroscopy and this value (1.46%) from 3 cycles freeze-thaw seeds were stated as 73.81% increased than untreated black seeds (0.84%). Other quality parameters, including moisture content, specific gravity, acid value, peroxide value, and iodine value, exhibited comparable properties between untreated and freeze-thaw pre-treated black seed oil (p < 0.05). Based on the analysis of thymoquinone content, black seed oil yield, and other related metrics, the 3-cycle freeze-thaw pretreatment emerged as the optimal method for enhancing cold-pressed thymoquinone content in black seed oil.
Morphological characterization of prioritized weed species at seedling stage in export-ready coir samples
(University of Peradeniya, Sri Lanka, 2023-09-20) Sirimalwatta, V.N.S.; Kumari, D.T.S.V.; Jayawardana, N.U.; Jayasuriya, K.M.G.G.; Yakandawala, D.M.D.; Gunasinghe, R.
Novel weed introductions have raised with the increased movements of goods and people. Hence, it is essential to detect and prevent the movement of weeds across borders. In Sri Lanka, the National Plant Quarantine Service (NPQS) is the main body that is responsible for regulate the movement of invasive weeds. Coir is one of the largest export commodities in Sri Lanka. Many countries are importing coir as a potting medium for soilless cultivation; thus, the free of certain weed species is a main concern. The NPQS uses grow-out tests for 21 days to check the presence of weed seeds in export-ready coir samples. However, the current practice is inadequate to accurately identify the weed contaminants. Therefore, rejection of coir consignments due to the presence of unconcerned weed species is a problem leading to a considerable economic loss. Seedling Identification Guides (SIG) are useful to identify key morphological characters at the seedling stage for some species and enable species identification. Thus, the main objective of the present study was to prepare a SIG for weed species [Crotolaria juncea L., Mimosa pudica L., Mimosa pigra L., Leucaena leucocephala (Lam.) de Wit, Lantana camera L., Convolvulus arvensis L., and Rumex sp.] frequently found in coir samples. Five seeds from each species were planted in four-inch-diameter plastic pots and kept in a contained space to prevent accidental weed escape. Fifteen morphological characteristics were recorded until true leaves arose. Among the observed characters, shape of the cotyledons and true leaves, and leaf texture were the most useful. Mimosa pigra and M. pudica can be distinguished by their cotyledon shape, leaf apex, and leaf base. Cotyledon shape, leaf apex, and leaf base are useful characters for distinguishing C. arvensis and Rumex sp. For quick and reliable identification, we recommend a suitable molecular approach.
The effect of pH and initial concentration on the degradation kinetics of glyphosate in biotic and abiotic waters
(University of Peradeniya, Sri Lanka, 2023-09-20) Dissanayake, D.A.T.W.K.; Mubarak, M.N.A.; Malavipathirana, S.; Ranasinghe, P.; Navaratne, A.N.
Glyphosate is one of the most commonly used herbicides globally. Microorganisms degrade Glyphosate into small molecules during its biodegradation. Biodegradation lowers its toxicity and reduces persistence in aquatic environments. The degradation kinetics of a pollutant is an important factor influencing its environmental fate. Therefore, in this study, the degradation kinetics of Glyphosate in waters was evaluated with respect to the zeroth and first-order models. Deionized water and well water samples were buffered to prepare abiotic and biotic waters at pH 4.5, 7.0 and 8.5, respectively, to c over the typical pH range of inland waters in Sri Lanka. pH-modified well water samples were separately spiked at 2, 10, and 100 mg L-1 with Glyphosate reference standard and glyphosate-based formulation. In low spiked levels in well water samples, the rates of degradation are given by the first-order rate constants with the same order of magnitude for both reference standard and commercial formulation. However, the 50% (DT 50) and the 90% (DT 90) degradation kinetics of formulation are comparatively higher than that of the reference standard. Although the microbial composition of the identical biotic well water samples is supposed to be constant; different microbial reactions may take place depending on the concentration. Therefore, different rate constants may be observed. Further, in the absence of microbes, significantly lower degradation rates were observed in the control study and all spiked levels followed the zeroth order. Moreover, the degradation of Glyphosate in water is independent of the pH in both abiotic and biotic waters. Further, the degradation rate depends on the initial concentration of Glyphosate in higher concentrations with no impact of the inert surfactant. However, the DT 50 and DT 90 are affected by the inert surfactant.