RESCON 2021

Permanent URI for this collectionhttps://ir.lib.pdn.ac.lk/handle/20.500.14444/5951

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Surfactant modified nano-montmorillonite as slow-release nitrate fertiliser
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Perera, U.M.P.K.; Jayarathna, L.; Yakandawala, D.M.D.; Seneweera, S.
The application of chemical fertiliser is the most straightforward way to increase crop yields. However, the overuse of fertilisers causes serious environmental hazards and human health problems. Most chemical fertilisers are inefficient because their nutrient release dynamics do not synchronise with plant nutrient uptake. As a result, most applied fertilisers tend to escape through leaching, adsorption, degradation, and surface runoff. We hypothesise that developing a biologically synchronised slow-release nano fertiliser (BSSRNF) will further improve nutrient use efficiency. Nitrogen (N) is the most important nutrient for all plant species, and it is primarily taken up in the forms of NH₄⁺ and NO₃⁻ . Surfactant modified montmorillonite (SMM) was developed as a carrier molecule to slow down the release of NO₃⁻ . MMT's surface area was increased to retain NO₃⁻ by treating with a cationic surfactant hexadecyltrimethylammonium bromide (HDTMA). Scanning electron microscopy, Fourier transform infrared analysis, X-ray diffraction, and thermogravimetric analysis were used to characterise the material's surfactant modification. Further, MMT was modified by using different combinations of HDTMA and the maximum ratio of NO₃⁻ to HDTMA absorbed was determined. It demonstrated that the material modification increased the surface capacity by a factor of nine when compared to the unmodified MMT. Also, the sorption of nitrate can be well described by the Langmuir sorption isotherm. It further demonstrated that the supply of NO₃⁻ from fertiliser-loaded SMM was available after 60 days of continuous leaching. These findings indicate that SMM can be adopted to deliver NO₃⁻ in a synchronised, slow-release manner and thus has enormous potential to improve plant fertiliser N use efficiency in cropping systems.
Metabolites of endophytic fungi associated with Syzygium aromaticum
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Samarakoon, K.; Perera, E.A.I.A.; Jayasekera, N; Yakandawala, D.; Kumar, N.S.; Adikaram, N.K.B.; Jayasinghe, L.; Araya, H.; Fujimoto, Y.
Plant endophytic fungi are an important source of renewable and environmentally friendly novel bioactive compounds. Hence, the present study investigated the chemistry of endophytic fungi isolated from leaves of Syzygium aromaticum L. (Myrtaceae), commonly known as cloves, a popular condiment plant used in indigenous medicine in Sri Lanka. They are commercially used for many medicinal purposes and in the perfume industry. In addition, clove is considered as one of the spices that can be potentially used as preservatives in many foods to replace chemical preservatives due to their antioxidant and antimicrobial properties. Fresh leaves of S. aromaticum were collected from the Central Province of Sri Lanka. Small segments (5 mm × 5 mm) of triple sterilised leaves were placed on Potato Dextrose Agar (PDA) and kept for incubation at room temperature (27 °C) for five to seven days in the dark until the appearance of fungal mycelium. The emerging fungus was subcultured to obtain pure cultures. Molecular identification of the isolated endophytic fungus is in progress. The pure fungal culture was inoculated into Potato Dextrose Broth (PDB), which was kept for 21 days with shaking at room temperature. The medium was filtered after 21 days, and the filtrate was partitioned with EtOAc (1:1). The residual mycelium was crushed and extracted with EtOAc. Both EtOAc extracts were combined based on the similarity of TLC. The chromatographic separation (silica gel column followed by Sephadex LH-20 and PTLC) of EtOAc extract resulted in campyrone C (1), campyrone A (2), campyrone B (3), pyrophen (4), 6-(1-hydroxy2-methylbutyl)-4-methoxy-2H-pyran-2-one (5), carbonarone A (6), dianhydroaurasperone C (7), fonsecinone D (8) and asperpyrone A (9). Therefore, endophytic fungi can be a promising source for isolating bioactive compounds beneficial for agriculture, industry and medicine.
Bioactivity of metabolites from Piper longum
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Bandara, H.M.S.K.H.; Amarasinghe, N.R.; Adikaram, N.K.B.; Jayasinghe, L.; Araya, H.; Fujimoto, Y.
Plant-derived extracts and compounds have been widely used to treat many diseases. Piper longum L. (Piperaceae), commonly known as long pepper, is widely distributed in the tropical and subtropical regions of the world. Dried fruits of P. longum are slender and aromatic. They are commonly used to treat stomach aches, bronchitis, cough and tumours. They are also applied externally to soothe and relieve muscular pains, rheumatism, paralysis and inflamed skin. Fruits of P. longum (400 g) were air-dried, powdered using an electric grinder and extracted successively with ethyl acetate (EtOAc) and methanol (MeOH) using a sonicator. Removal of the solvent afforded 12 g of EtOAc and 21 g of MeOH extracts. It was subjected to silica gel, Sephadex LH-20 and reversed-phase silica gel columns and resulted in three UV active compounds guineesine (1), pipatalin (2) and 4',7-dimethylapigenin (3). All the compounds were subjected to enzyme inhibitory assays α-amylase, α-glucosidase, acetylcholinesterase and lipase. They were also screened for antioxidant activity using DPPH radical scavenging method, antifungal activity against Cladosporium cladosporioides, phytotoxicity by lettuce seed germination assay and brine shrimp toxicity against Artemia salina. All compounds showed moderate brine shrimp lethality with IC₅₀ of 66.71 ppm, 30.53 ppm and 35.63 ppm, respectively. Strong antioxidant activity was observed for compound 1 against DPPH radical with IC₅₀ 0.03 ppm. Compound 2 showed both root and shoot inhibition of lettuce seedlings at 243.58 ppm and 169.43 ppm, respectively. Moderate α-glucosidase and weak α-amylase inhibitory activities were observed for compound 3 at 58.12 ppm and 667.28 ppm, respectively. None of the above compounds exhibited acetylcholinesterase, α-amylase and lipase enzyme inhibitory activities and antifungal activity. These findings suggest P. longum fruits could be a potential source for new therapeutic agents.
Careya arborea stem bark: source of potential therapeutic agents
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Bandara, H.M.S.K.H.; Amarasinghe, N.; Adikaram, N.K.B.; Jayasinghe, L.; Araya, H.; Fujimoto, Y.
Natural products originating from plants and microorganisms have been widely used to treat many diseases. Many records have shown the use of such substances by humans for thousands of years. Careya arborea, commonly known as wild guava, is a medium-sized deciduous tree that belongs to the Family Lecythidaceae. The stem bark is used in the treatment of tumours, bronchitis, epileptic fits and skin diseases. It is also used as a remedy for diarrhoea dysentery with bloody stools and ear pain. Careya arborea stem bark was air-dried and powdered using a grinder. The powdered sample was sequentially extracted with ethyl acetate (EtOAc) and methanol (MeOH) using a sonicator. Removal of the solvents afforded EtOAc and MeOH extracts. The two extracts were subjected to silica gel, Sephadex LH-20 and reversed-phase silica gel columns to yield five compounds Lupeol caffeate (1), Epigallocatechin-3-gallate (2), Gallocatechin (3), Epigallocatechin (4) and Lupeol (5). All the compounds were subjected to enzyme inhibitory assays; α-amylase, α-glucosidase, acetylcholinesterase and lipase. Compounds were screened for antioxidant activity using DPPH radical scavenging method, antifungal activity against Cladosporium cladosporioides, phytotoxicity by lettuce seed germination assay and toxicity against brine shrimp, Artemia salina. Compound 2 showed moderate brine shrimp lethality (LD₅₀ 71.29 ppm). Strong antioxidant activity against DPPH radical was observed for all five compounds, and strong α-glucosidase inhibitory activity was observed for compounds 2, 3 and 4 (IC₅₀ 0.89, 3.80 and 0.25 ppm, respectively). Moderate acetylcholinesterase inhibitory activity was exhibited by compound 2 (IC₅₀ 85.92 ppm) and compound 5 (IC₅₀ 90.33 ppm), while compound 3 showed strong acetylcholinesterase inhibitory activity (IC₅₀ 9.51 ppm). Out of all, compound 3 exhibited mild α-amylase inhibitory activity (IC₅₀ 111.81 ppm), and compound 2 showed lipase inhibitory activity (IC₅₀ 179.85 ppm). These results suggest that C. arborea could be a potential source for the isolation of new therapeutic agents.
Identification of cellulolytic Penicillium sp. and production and characterisation of its enzyme
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Gunatilake, K.S.; Samaraweera, P.
Cellulase is an enzyme complex consisting of exoglucanase, endoglucanase and β-glucosidase that acts synergistically to degrade cellulose matter. Fungal cellulases are widely used in industrial applications due to their high activity, availability and high stability. Trichoderma, Penicillium and Aspergillus are the most reviewed cellulolytic fungi, while Trichoderma is used in commercial level cellulase production. However, recently Penicillium sp. has gained attention as an efficient cellulase producer that might even outperform Trichoderma sp. Therefore, this study aimed to identify a soil cellulolytic Penicillium sp., characterise its extracellular cellulase, and optimise the growth media for the secretion of the enzyme. Pure fungal colonies were obtained, and initial screening for cellulolytic ability was carried out using Congo red and Gram's Iodine methods. Crude cellulase was characterised for optimum pH, temperature and effect of ions on cellulase activity. The fungal growth medium was optimised with respect to a carbon source, nitrogen source and pH, for cellulase production. Identification of the fungal species was carried out using morphological and molecular methods, where Internal Transcribed Spacer (ITS) based PCR amplification followed by sequencing was performed. Based on sequence similarity, the cellulolytic fungal species was identified as Penicillium sumatraense. The crude enzyme showed the highest activity at pH 4.0 and 60 °C, while the addition of Mn²⁺ ions increased the enzyme activity significantly. The fungus secreted high levels of enzyme when cellulose and NaNO₃ were used as carbon and nitrogen sources, respectively, and the pH of the medium was 6.0. Further studies related to the thermostability of Penicillium sumatraense cellulase and its efficiency compared to other cellulolytic fungi have to be performed.
Identification of a lipolytic Trichoderma sp. and characterisation of its extracellular lipase
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Athukorala, N.K.; Samaraweera, P.
Fungal lipases are used in many industries due to their low production cost, catalytic activity, ability to tolerate polar organic solvents and stability at high temperatures. The demand for lipases has kept researchers exploring new lipolytic fungi. However, the success of such studies lies in the optimisation of the growth conditions to maximise lipase secretion and characterisation of the enzyme activity. Therefore, the current study aims to characterise the crude enzyme extracted from a lipolytic Trichoderma sp. and identify the fungus to species level. The Trichoderma sp. was isolated from soil, and the lipolytic activity was determined qualitatively and quantitatively. The growth medium of the lipolytic Trichoderma sp. was optimised for carbon source, nitrogen source, and pH. The effect of pH, temperature, cations, and anions for the crude lipase activity was analysed. Total genomic DNA was extracted for species-level identification, and Internal Transcribed Spacer (ITS) region was amplified using ITS 1 and ITS 4 primers and sequenced. The results of the study revealed the dependence of extracellular lipase production on growth conditions. Maximum lipase secretion was observed with olive oil as the carbon source and ammonium sulfate as the nitrogen source at a pH of 7.0. The crude lipase activity was high at a pH of 6.0 and 40 °C. The significant lipase activity at high temperatures revealed the potential applications in industries. Moreover, Ca²⁺ and NO₃⁻ enhanced the crude lipase activity. Database analysis of the sequenced DNA region revealed the fungus as Trichoderma longibrachiatum. The study showed that the lipolytic T. longibrachiatum could be improved for industrial applications. Furthermore, the enzyme characterisation revealed the industrially important properties of the crude lipase extracted from the lipolytic Trichoderma sp.
Bioactivity and wound healing properties of selected plants
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Silva, M.C.G.; Uduwela, D.R.; Jayasinghe, J.M.S.; Gunathilake, W.S.S.; Ekanayake, E.W.M.A.; Dissanayake, U.P.R.U.
Herbs as traditional therapy for wound healing and skin regeneration is common in Asian countries such as China, India and Sri Lanka. The phytochemicals in these herbs may possess antioxidant, anti-inflammatory, antibacterial activities, and cell migration and proliferation properties to provide tissue remodelling, which helps heal wounds. The aim of this research was to investigate the wound healing properties of Coffea arabica (coffee), Murraya koenigii (curry leaves), and Tabernaemontana dichotoma (poison nut) leaves. The extracts were prepared using dried, powdered leaves where water and water-acetone (v/v 1:1) extracts were obtained using a bottle shaker and hot water extracts by Soxhlet extraction. Nine extracts were prepared and assessed for antioxidant activity by DPPH radical scavenging assay and FRAP assay. Their anti-inflammatory activity was determined by heat-induced hemolysis assay and antibacterial activity by broth microdilution assay against six bacterial strains representing gram-positive and gram-negative strains. Water-acetone extracts exhibited the highest activities, amongst which coffee leaves water-acetone extract showed the best activity. Coffee leaves water-acetone extract showed the lowest IC₅₀ value of 27.44 ± 1.12 ppm in DPPH assay, the highest FRAP value of 24.25 ± 0.98 mmol dm-3 g ⁻¹ in FRAP assay, the lowest IC50 value of 280.00 ± 19.88 ppm in anti-inflammatory assay and the lowest MIC values ranging from 25.00 mg ml⁻¹ to 6.25 mg ml⁻¹ against the six bacterial strains tested. Coffee leaves wateracetone extract showed the highest activities in antioxidant, anti-inflammatory and antibacterial assays suggesting that it may possess the highest wound healing properties among the nine extracts investigated in this study.
Biofilm biofertiliser enhances the composition and capacity of antioxidants in rice grains
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Rathnathilaka, A.T.D.; Premarathna, M.; Madawala, H.M.S.P.; Seneviratne, G.
Rice (Oryza sativa L.) is the staple food in Sri Lanka, and it is an important source of vitamins, minerals, fibres and antioxidants. Rice antioxidants influence the cellular redox status of human plasma, which could offer protection against chronic diseases such as cancers and diabetes, those known to be associated with oxidative stress. However, there is a dearth of information about the effects of biofertilisers on antioxidant composition and capacity in rice grains. The available evidence suggests a higher prevalence of antioxidants in organic rice than in rice grown with chemical fertiliser. Therefore, this study investigated the effect of Biofilm biofertiliser (BFBF) on antioxidants and antioxidant capacity of rice grains. Rice seed samples (n = 90) were collected at the harvest from 18 farmer-managed paddy fields that were under two different fertiliser applications; 100% chemical fertiliser (CF) practice (425 kg NPK/ha) and 50% CF practice + BFBF (2.5 L/ha) in the Ampara District. The samples were analysed for total phenolic content (TPC), total flavonoid content (TFC) and total antioxidant capacity (TAC). The data were statistically analysed using a t-test following the confirmation of normal distribution. Pearson correlation coefficients (r) were calculated to determine the relationships among TPC, TFC and TAC using Minitab 17 version. The results revealed that the application of 50% of CF practice + BFBF significantly increased (p < 0.05) the production of TPC by 67%, TFC by 45%, and TAC by 80% in rice grains over 100% CF practice. Furthermore, TAC was found to be positively correlated with TPC (r = 0.871; p > 0.0001) and TFC (r = 0.868; p < 0.0001). Thus, the results confirmed that the application of BFBFs increased the content and the capacity of antioxidants in rice grains.
Isolation of halotolerant fungi from pickled food and their growth performances in different saline conditions
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Makuldeniya, M.W.M.T.U.G.; Dhanapala, M.P.C.S.
Highly concentrated salt is one of the oldest food preservation techniques used by communities worldwide for centuries. A high concentration of salt makes an unfavourable environment for microbial growth by creating a water stress environment. Pickling is one of the widely used food preservation methods based on the use of high salt concentrations. But the most pliable food pathogens like fungi can still contaminate salt-persevered food. Fungi that can tolerate high salt concentrations are known as halotolerant fungi. Most of the salt-tolerant fungal species belong to the phyla Ascomycota and Zygomycota. Penicillium is one of the well-studied fungal genera, while the genus Mucor has many industrial applications. These fungi are reported as processed food spoiling fungal genera. Most of the species belonging to the genus Penicillium can tolerate higher salt concentrations, closer to 20% NaCl. Most of the species that belong to the genus Mucor can tolerate 3% NaCl without distracting their enzymatic activities. In this study, a few halotolerant fungal species responsible for contaminating pickled lime were isolated and identified based on colony characteristics and reproductive morphology. Furthermore, the salt-tolerant ability of the isolated fungi was tested using a modified PDA medium consisting of different salt concentrations. The NaCl concentration series was designed from 0.0 mold m⁻³ to 1.0 mold m⁻³ with 0.2 intervals. Based on the colony characteristics and microscopic features, the isolates were identified as Penicillium sp. and Mucor sp. Penicillium sp. recorded the highest growth in 1.0 mold m⁻³ NaCl medium, and it was more stable than Mucor sp. at higher salt concentrations. Mucor sp. showed the optimum growth at 0.2 mold m⁻³ NaCl, and the growth decreased with the increasing salt concentration.
In vitro antioxidant and antihyperglycemic activities of plant extracts of Garcinia zeylanica
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Abesingha, A.M.A.K.; Jayasingha, J.M.S.; Sampath, S.N.T.
Garcinia zeylanica (Kaha goraka/Ela goraka), belongs to the genus Garcinia, Family Clusiaceae and is among the five endemic Garcinia species in Sri Lanka. It is also a globally endangered plant. This species shows similar morphology to G. quaesita (Rath goraka). The dried fruits of both species are used in Ayurveda and as a savoury agent in cooking. However, very little attention has been given to G. zeylanica compared to the G. quaesita in the scientific exploration of biological activities. Hence, we studied the in vitro antioxidant and antihyperglycemic activities of the fruits (F), leaves (L) and bark (B) of G. zeylanica. Nine crude extracts were obtained by sequential extraction of plant parts with hexane (HX-L, HX-F, HX-B), ethyl acetate (EA-L, EA-F, EA-B) and methanol (MT-L, MT-F, MT-B). The presence of antioxidants in all plant parts was confirmed by qualitative evaluation using the TLC bioautography method, and all nine plant extracts showed the presence of antioxidant compounds in varying degrees. The antioxidant potential was evaluated quantitatively using DPPH radical scavenging assay. The antihyperglycemic activity was evaluated using the α- amylase inhibition assay. Nonpolar extracts showed a very high free radical scavenging ability compared to polar plant extracts, while the MT-B showed a significantly low IC₅₀ (13.81 ± 0.13) mg L⁻¹ despite being polar. HX-F extract showed very high antioxidant activity (13.53 ± 0.02) mg L⁻¹ compared to that of HX-L (46.57 ± 2.93) mg L⁻¹, and HX-B (44.86 ± 0.01) mg L⁻¹ extracts, and it also showed a very low IC₅₀ with a closer value to the ascorbic acid (7.30 ± 0.75) mg L⁻¹, which is the standard. HX-F showed the lowest IC₅₀ value (28.08 ± 1.09) mg L⁻¹ in α- amylase inhibition assay indicating very high antihyperglycemic activity compared to the HX-L and HX-B. These empirical data showed that there is significant antioxidant activity and antihyperglycemic activity in G. zeylanica.
Comparative evaluation of phytochemical constituents in leaves of four selected medicinal plants
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Panambara, P.A.H.R.; Rajkumar, G.; Sanmugarajah, V.
Diabetes mellitus is a major epidemic worldwide. The anti-diabetic activity of medicinal plants is due to the presence of phytochemicals and other ingredients which demonstrate hypoglycemic activity. Some individuals prefer traditional medicines for diabetes as they believe these have fewer side effects. The present study analysed the phytochemical constituents in leaves of four selected medicinal plants: Murraya koenigii, (Curry leaf) Tinospora cordifolia (Moonseed), Enicostemma axillare (Indian whitehead) and Gymnema sylvestre (Cow plant), known for their anti-diabetic properties. The leaves of medicinal plants were collected, and their identification was authenticated at the National Herbarium, Royal Botanic Gardens Peradeniya. The shade dried leaves were powdered and extracted with ethanol using the cold extraction technique. The ethanolic extracts of each medicinal plant leaf powder were used to detect the presence of phytochemicals. The total phenolic, tannin and flavonoid contents were evaluated by the colourimetric method. Tannin, saponins, alkaloid, glycosides, steroids, phenols and coumarins were found in leaf extracts of all plants. Terpenoids, quinone and anthraquinones were only found in M. koenigii and E. axillare. Total phenoli contents (mg GAE/g) varied from 325.60 ± 23.84 (T. cordifolia) to 1960.70 ± 66.88 (M. koenigii), Flavonoid contents (mg GAE/g) ranged from 15.03 ± 1.42 (T. cordifolia) to 22.270.86 (E. axillare). The total tannin content (mg/ml) of all four varieties is almost similar (1.24 ± 0.01). Higher alkaloid content was found in M. koenigii (19.42 ± 0.26%). This study revealed that the ethanolic extract of leaves of all plant species contains basic phytochemicals, and M. koenigii is richer with important phytochemicals, followed by E. axillare. Therefore, Enicostemma and Murraya species can be used as nutraceuticals in traditional medicine.
Effect of microplastics on growth of solanum lycopersicum and soil arbuscular mycorrhizal fungi
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Weerasinghe, W.M.T.M.; Madawala, H.M.S.P.
Microplastic (MP) contamination of agricultural soils is a major concern today. Here we investigated the effects of MPs on the growth of Solanum lycopersicum and Arbuscular Mycorrhizal Fungi (AMF) abundance. A pot experiment was conducted in a glasshouse using garden soil mixed with two types of MPs, microfibers (MFB) and microfilms (MFL), to achieve MP concentrations, 0.0, 0.4, 2.4, 4.4, 6.4 and 8.4%. Ten seedlings of S. lycopersicum were raised per pot from seeds and left only two seedlings per pot. Six replicates were used for each treatment. Plant height was measured weekly for 13 weeks before harvesting destructively. Relative growth increment (as a percentage of the initial height), relative growth rate (RGR), root weight ratio (RWR) and root: shoot ratio (RSR) were calculated. Chlorophyll levels were quantified spectrophotometrically using randomly selected mature leaves. The AMF spores were quantified by extracting spores using the wet sieving and decanting method. Irrespective of the MP type, a concentration-dependent reduction in growth increments over time was detected compared to the control (with no MPs). After 13 weeks, the RGR also showed a similar reduction in the presence of MPs (F = 13.74; p ≤ 0.0001). The RSR gradually declined with the increasing levels of MPs. The decline in RSR was due to reduced biomass allocation to aboveground parts (55 and 40% decline with MFL and MFB, respectively) compared to a 6 and 22% decline in root allocations (compared to control plants). Plants grown with MFBs had significantly higher chlorophyll content than MFLs (F = 18.33; p ≤ 0.0001). Despite the type, MPs also significantly reduced the AMF spore density (F = 108.1; p ≤ 0.0001), confirming their negative role on soil microbes. The smallest and the largest spores (< 45 μm and > 500 μm) were notably more prevalent in soils without MPs than soils with MPs. Overall, results suggest that MPs negatively influence the vegetative growth of S. lycopersicum and the abundance of AMF spores. Understanding the impacts of MPs on the soil-plant system is imperative to minimise risks posed by soil MPs in agriculture.
Accumulation of essential and toxic elements in Sri Lankan rice (Oryza sativa l.)
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Manawasinghe, K.S.; Chandrajith, R.; Seneweera, S.
Rice is the staple food in many Asian countries, including Sri Lanka, and has a high demand because it provides essential carbohydrates, protein, and minerals. Among essential minerals, zinc (Zn) and iron (Fe) are globally deficient and are more common among rice-consuming populations. Rice plants also accumulate toxic elements, especially arsenic (As) and cadmium (Cd), which can cause serious health issues. Close attention is currently given towards cultivating high-quality rice that is less in toxic elements and high in nutrient values. However, there is a lack of information on trace element accumulation of Sri Lankan traditional rice genotypes. Therefore, a glasshouse experiment was conducted using genetically diverse ten rice cultivars with three replicas to assess toxic and essential elements in rice grains, and rice grains were analyzed using an ICP-MS. The varietal difference in Fe accumulation was significant, and the highest accumulation was observed in Beheth heenati, while At 362 and Bg 300 were identified as lower Fe accumulating varieties. The highest Zn accumulation was shown by Kahawanu, followed by Pachchaperumal and Beheth heenati. The native variety, Behethheenati, accumulated a higher amount of essential trace elements, including Zn, Fe, Mn, Ni, Co, V, Mo, and Cu. The highest Cd accumulation was observed in At 362 while Bg 300 showed the lowest, followed by Madathawalu and Kahawanu. Arsenic has shown a significant difference in their accumulation in different varieties. The highest As accumulation was observed in Kalu heenati, while the lowest was found in At 362, followed by Kahawanu and Bg 300. Among the cultivar tested, Kahawanu and Bg 300 were identified as relatively lower in both As and Cd concentrations in grains. As a result, these genotypes can be used in further studies on developing varieties with high nutrients and low toxic elements while achieving other desired characteristics.
Nutritive value of grass species palatable to sambar deer (Rusa unicolor) in Horton Plains National Park
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Weerasekera, D.S.; Mahipala, M.B.P.K.; Weerasinghe, W.M.P.B.; Weeratunga, M.W.D.C.; Udagama, U.W.G.D.N.; Perera, S.J.; Ranawana, K.B.
Sambar deer (Rusa unicolor) is classified as a browser since it secretes viscous saliva and consists of the relatively less stratified rumen. However, they often gathered in herds for communal grazing in Horton Plains National Park (HPNP) grasslands dominated by native Chrysopogon zeylanicus and introduced Pennisetum cladestinum and Pennisetum glabrum species. The present study investigated the nutritional value of more palatable grass species for sambar in HPNP grasslands. Grazing sambar was observed along a transect from Pattipola entrance to Ohiya in HPNP at three observation circles (100 m radius) from 6:00 to 8:00 hours and 15:00 to 18:00 hours on three consecutive days of every month during 2020. The grass patches where sambar grazed in higher numbers were assumed to contain more palatable grass species. In each observation circle, those grass patches were marked, and the species composition was recorded using a quadrat (n = 6). The most common grass species was P. cladestinum followed by P. glabrum, C. zeylanicus, Garnotia exaristata, and Andropogon lividus. Edible plant matter of the most common five grass species was collected (n = 6), and proximate composition, organic matter digestibility (OMD), and metabolizable energy content (ME) were estimated. The most palatable P. cladestinum had the highest (p < 0.05) crude protein (CP) percentage (10.46 ± 0.37), followed by P. glabrum (8.27 ± 0.57). The CP percentages of less palatable C. zeylanicus, G. exaristata, and A. lividus (7.46 ± 0.23, 6.60 ± 0.15, and 6.73 ± 0.14, respectively) were lower than P. cladestinum (p < 0.05). The native grass species in HPNP, C. zeylanicus had the lowest (p < 0.05) OMD (33.51 ± 1.43%) and ME (4.9 ± 0.21 MJ/kg). The results suggested that high CP percentage in P. cladestinum caused sambar in HPNP to shift from browsing to grazing, and further studies are needed for confirmation.
Increased intestinal absorption of chlorogenic acid promoted by coconut oil reduces macromolecular damage in humans
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Weerakoon, W.M.T.D.N.; Jayathilaka, N.; Seneviratne, K.N.
Antioxidants in the body can reduce oxidative stress. Reports indicate that medium-chain fatty acids (MCFAs) absorb small polar drug molecules. Coconut oil has a high percentage of MCFAs. Our previous studies indicate that coconut oil enhances the absorption of antioxidants such as caffeic acid in rats and chlorogenic acid in humans. The present study was conducted with human volunteers to study the effect of enhanced absorption of chlorogenic acid on the oxidation of macromolecules (lipids and proteins). Ethical clearance for the study was obtained from the Ethics Review Committee of the University of Kelaniya. The study involved three groups with 30 volunteers in each group. Group 1 received a gelatinous capsule with chlorogenic acid (450 mg) and coconut oil (1.00 mL), while Group 2 received a gelatinous capsule with chlorogenic acid (450 mg) and soybean oil. The control group received a gelatinous capsule containing only chlorogenic acid (450 mg). The control group reflects the baseline of the chlorogenic acid absorbed from food. Based on previous studies, blood samples were collected one hour after the oral administration of the capsule. Inhibition of lipid peroxidation in plasma was assessed by Thiobarbituric acid reactive substances (TBARS) assay. TBARS level of Group 1 (0.003 ± 0.001 μmol/mL) was significantly different (p ≤ 0.05) from that of Group 2 (0.007 ± 0.001 µmol/mL) and the control group (0.010 ± 0.001 µmol/mL). Inhibition of protein oxidation in plasma was assessed by protein carbonyl assay. Protein carbonyl level in Group 1 (0.98 ± 0.11 nmol/mL) was significantly different (p ≤ 0.05) from those of Group 2 (2.06 ± 0.13 nmol/mL) and control group (2.49 ± 0.29 nmol/mL). The results indicate that the intestinal absorption of chlorogenic acid improves the antioxidant status of blood, thus protecting lipids and proteins from oxidative damage.
Rice blast disease outbreak in 2020/2021: cross-sectional analysis
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Pabasara, M.D.; Rajakaruna, R.W.M.T.N.; Yapa, K.V.; Ekanayake, E.M.I.J.S.B.; Ariyarathna, H.A.C.K.
Annually, over 30% of rice harvest is lost due to blast disease caused by Magnaporthe oryzae worldwide. In 2020, the“Maha” season reported a blast outbreak in the country. This analysis aimed to assess the damage due to the blast outbreak in terms of disease incidence and severity. Infected fields were studied in six districts: Kilinochchi, Anuradhapura, Kandy, Ampara, Gampaha, and Monaragala. Two fields were studied from each district using three 1 m² randomly selected quadrats. Damage due to the disease was estimated based on standard protocols and farmers interviews. During the interviews, farmers claimed that the disease condition coincided with wet weather. They explained that from the first symptom, which was “sudu karal” or “whiteheads” that randomly cropped up among healthy bushes, the entire fields appeared “burnt” within 24 to 48 h. Due to fast disease development, the curative application of fungicides was neither practical nor successful. Cultivars grown in the sites: BG 367, BG 300, BG 359, and BG 1/94 were susceptible to panicle blast, and the yield loss can be up to 100%. Wherever the disease severity was low between zero to four scale, disease incidence was also low at 25%. However, the same cultivar in severely infected fields on a six to nine scale showed a high disease incidence of 40% to 80%. Furthermore, fields adjacent to severely infected fields, where the same cultivar was grown but with three to a seven-day difference in growth stage, did escape the disease. Therefore, other than the susceptibility of the cultivar, prevailing weather conditions and the crop growth stage or other factors can critically affect disease incidence and severity. Thus, while the results highlight the importance of crop calendar and good agricultural practices (GAPs), further studies on the climate factors and the development window that triggers the disease can help accurate disease forecasting.
Post-dispersal survival and germination of seeds of Pterocarpus marsupium and Elaeocarpus ganitrus
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Alahakoon, A.A.C.B.; Daulagala, P.W.H.K.P.
Pterocarpus marsupium (native) and Elaeocarpus ganitrus (exotic) are two tree species that produce a large number of fruits every season. However, the seed germination of these two species is poor or delayed. This study evaluated the survival and germination of seeds of the two species after dispersal. Fresh, healthy fruits filled with seeds at dispersal were collected. Seed germination (SG) of P. marsupium with and without mechanical scarification was tested under laboratory conditions (20 × 5 seeds per treatment). In E. ganitrus, germination of intact seeds and seeds exposed by breaking the endocarps was tested in distilled water and 500 ppm gibberellic acid (GA₃) (10 × 5 seeds per treatment). Data were recorded weekly for four weeks. Four replicates of 50 and 25 fruits of P. marsupium and E. ganitrus, respectively, were buried at two depths (0 and 3 cm) in plastic mesh containers filled with soil. Seedlings that emerged were recorded after three months, and surviving seeds were exhumed, and SG was tested. Initially, the seeds present per 100 fruits (SF₁₀₀) of P. marsupium and E. ganitrus were 73 and 100, respectively. Mechanical scarification increased SG of P. marsupium (93%) compared to non-scarified seeds (12%; p < 0.05), however, none of the E. ganitrus seeds were germinated. In the burial experiment, SF₁₀₀ of P. marsupium had declined to 24 (16 germinated after scarification) and six (five germinated after scarification; p < 0.05) at 0 and 3 cm depths, respectively producing < 20 seedlings per 100 fruits. In E. ganitrus, SF₁₀₀ was 88 at 0 cm, out of which 66 (75%) germinated in 500 ppm GA₃ after breaking the endocarp. At 3 cm depth, SF₁₀₀ was 86, of which 50 (58%) germinated in 500 ppm GA₃ after breaking the endocarp. The post dispersal survival of seeds was low in P. marsupium compared to E. ganitrus and was higher at the soil surface (0 cm depth).
Morphological diversity of external male genitalia of seven mosquito genera in Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Anuradha, G.N.P.V.; Weeraratne, T.C.; Chathuranga, W.G.D.; De Silva, W.A.P.P.
Structural variations of external male genitalia are promising identification features of mosquitoes. The present study was aimed to determine the generic and species-specific variations of male genital structures of common mosquito species in Sri Lanka. Larvae and adult mosquitoes were sampled from September to November 2020 from selected sites in the Kandy district. Larvae were reared to adult, and male mosquitoes were separated from the colony. Light trap samples were carefully observed to separate male mosquitoes. Standard taxonomic keys were used for identification. Genitalia of 52 male mosquitoes belonging to seven genera and 15 species were separated and slide-mounted using Canada Balsam. Detailed images of mounted genitalia were photographed using a micro-image system. Structural variations were reported from the basal lobe, basistyle, claspette, phallosome and dististyle of male genitalia. Aedes mosquitoes were characterized by the clump of setae present in the basal lobe. Filament and row of setae in the claspette were used to differentiate Aedes albopictus, Aedes aegypti and Aedes greenii. Globular structure in the dististyle was unique to Aedes vittatus. Genus Anopheles was characteristic of the spines present at the base of the basistyle. Globular structure in the claspette end was a distinctive feature of Anopheles maculatus. Armigeres mosquitoes were characterized by the presence of tooth-like structures along the dististyle. Dense setae on the basistyle was specific to Armigeres subalbatus. Outward curved dististyle was a prominent feature of Coquilletidia crassipes. A crown-like structure with a comb of teeth in the tenth sternite and appendages on the subapical lobe was characteristic of Culex. Orthopodomyia species were distinguished with the number of spines on the basal lobe. The structure of the phallosome was unique to Toxorynchites mosquitoes. Generic and speciesspecific features of male genitalia reported from this study are essential in identifying mosquito species complexes in Sri Lanka.
In vitro antimicrobial activity of Panchavalkala, an ayurvedic herbal formula: preliminary study
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Fernando, A.M.A.; Jayatilake, J.A.M.S.
Panchavalkala is a water extract of a combination of barks of five medicinal plants, widely used to treat wounds in Ayurvedic medicine. Three different combinations are commonly used as Panchavalkala in Sri Lanka. This study evaluated the in vitro antimicrobial activity (AMA) of three different combinations of Panchavalkala against common pathogens: Escherichia coli, Pseudomonas auregenosa, Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA) and Candida albicans. The combinations of Panchavalkala were prepared using pure raw materials according to the ayurvedic formulae. They were named A, B, and C and 60 g of total weight was used for water extraction and concentrated into 8:1 by boiling from each combination. Screening of AMA for each sample was carried out using the agar well diffusion assay in quadruplicate. Zones of inhibition of samples A, B, C against S. aureus and MRSA were 4.81 ± 0.26 mm, 4.69 ± 0.26 mm, 4.25 ± 0.27 mm, 3.88 ± 0.23 mm, 5.12 ± 0.23 mm, 4.50 ± 0.38 mm, respectively. Growth of S. aureus was significantly inhibited by sample C compared to amoxicillin used as a positive control (p = 0.01). Samples A and C showed a significant effect against MRSA compared to vancomycin (p = 0.01). None of the above combinations of Panchavalkala had an inhibitory effect on E. coli, P. auregenosa and C. albicans. All three combinations were effective against S. aureus, including MRSA in vitro. Further studies are recommended to explore the AMA of Panchavalkala used in Sri Lanka.
In vitro cytotoxicity of Carica papaya crude leaf extract
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Galappaththi, M.O.; Abeykoon, A.M.S.B.; Muthuwaththa, M.G.C.M.; Noordeen, F.
Plant-based compounds are an option for the development of new antiviral drugs. Asians commonly use papaya (Carica papaya) leaves to treat dengue without an understanding of its toxicity, if any. The objective of the study was to screen in vitro cytotoxicity of C. papaya leaf extract against normal African green monkey kidney epithelial cell line (Vero) cells. CytoTox 96® Non-Radioactive Cytotoxicity Assay (Promega, USA) is a colourimetric assay, which quantitatively measures lactate dehydrogenase (LDH) released upon cell lysis. Carica papaya leaf extract was prepared in a two-fold dilution series. Two, 96 well assay plates, were prepared with Vero cells and, the assay was set up with an analytical system based (i) Negative control - without Vero cells, (ii) Vehicle control - untreated cells, (iii) Positive control - lysis solution with four replicates. Carica papaya extract was added to the test wells at different concentrations and, one set of plates was incubated for 5 h at 37 °C and the other set for 24 h at 37 °C. The absorbance data were measured using a standard 96-well plate reader (Labtech LT4500, Singapore) and the percentage cytotoxicity was calculated for each concentration tested. Colour intensity and the absorbance values decreased with the decrease of concentration of leaf extract. The percentage cytotoxicity for dilutions, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, 1/256, 1/512, 1/1024 was 95.60, 71.53, 74.77, 82.16, 79.91, 40.25, 7.37, 0.16, -1.24, respectively, for the 5 h and 141.61, 133.24, 127.78, 121.88, 109.79, 106.67, 30.64, 22.67, 25.39, respectively for 24 h. Higher concentrations of the extract caused higher cell lysis showing cytotoxic effects Vero cells at dilutions < 1/256. The information about the cytotoxicity levels helps select the minimum toxic concentrations of C. papaya leaf extract against the antiviral activity of the dengue virus.

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