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Comparative in vitro antidiabetic activity of two amides from black pepper seeds (Piper nigrum l.) against postprandial glucose regulatory enzymes
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10) Sampath, S. N. T. I.; Jayasinghe, J. M. S.; Attanayake, A. P.; Karunaratne, V.
Postprandial high blood sugar could be a risk factor for diabetes mellitus, and this condition is one of the critical points in diabetic treatments. Medication of postprandial hyperglycemia could be attained by mainly inhibiting key regulatory enzymes such as α-amylase and α-glucosidase, which are involved in carbohydrate digestion. Herbal plants are an excellent source to treat this disease and improve the ease of health. Piper nigrum L. (black pepper) is a well-known herbal plant belonging to the Family Piperaceae, and it contains a higher number of bioactive compounds. The present study reports the anti-postprandial hyperglycemic activity of an amide (pipnoohine) isolated from the hexane extract of P. nigrum seeds and compares it with that of isolated piperine (an antidiabetic compound from P. nigrum plant) and commercially available acarbose (a standard antidiabetic drug). The piperine and pipnoohine have been previously isolated from the genus Piper (P. nigrum, Piper longum, Piper chaba). However, the comparison of in vitro anti-postprandial hyperglycemic activity of these two compounds is untapped up to date. The two compounds were isolated from hexane extract of P. nigrum seeds using chromatographic techniques (vacuum liquid chromatography and flash column chromatography), and they were identified as piperine and pipnoohine, using ¹H and ¹³C NMR, liquid chromatography-mass spectrometry (LC-MS), UV, IR spectroscopy and melting point data. The in vitro anti-postprandial hyperglycemic activity of the isolated compounds was determined in terms of the 50% inhibitory potential of α-amylase and α- glucosidase enzymes. Both piperine and pipnoohine inhibited 50% of α-amylase enzyme activity at 37.04±0.94 and 62.22±2.06 mg l⁻¹ concentrations, respectively. In the α-glucosidase assay, the piperine and pipnoohine inhibited 50% of the enzyme activity at 51.12±0.09 and 82.42±2.25 mg l-1 concentrations, respectively. The pipnoohine showed no significant difference between the above activities with the piperine (p>0.05). The acarbose inhibited 50% of the α-amylase and α-glucosidase enzymes at concentrations of 5.72±0.33 and 17.72±0.48 mg l⁻¹, and the activities, however, showed significant differences with the inhibition activities of piperine and pipnoohine (p<0.05). This is the first report of α- amylase and α-glucosidase inhibitory activities of pipnoohine and the comparison of in vitro anti- postprandial hyperglycemic activity of piperine and pipnoohine. Results concluded that pipnoohine exerted considerable α-amylase as well as α-glucosidase inhibitory activities that indicate that it also can be considered a drug lead for the treatment of diabetes mellitus.
Shell morphometry and radulae analysis of freshwater gastropod genus paludomus
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Liyanagedara, P.H.; Wathuliyadde, N.; Kumburegama, S.
Paludomus is the most common genus represented among freshwater gastropods in Sri Lanka. Of the 12 recorded Paludomus species, 10 are endemic to the country. Shell morphology is the major taxonomic feature that has been used for their identification. However, the identification of Paludomus species using shell features is ambiguous due to shell plasticity and homoplasy. One characteristic that can be reliably used in the systematic identification of gastropods is the radula, unique molluscs feeding structure. Five species of Paludomus were identified (Paludomus chilinoides, P. bicinctus, P. decussatus, P. neritoides, P. sulcatus) using shell morphology from 47 sampling sites spanning the Kandy, Matale and Nuwara Eliya districts. Different shell morphometries, i.e. Shell Height (SH), Shell Width (SW), Aperture Height (AH) and Aperture Width (AW), were measured using a digital Vernier calliper, and shell indices were calculated. A Principal Component Analysis (PCA) was conducted to check whether the species/morphotypes can be distinguished using shell morphometry. Furthermore, the median, lateral and marginal teeth of the dissected radulae were examined using Scanning Electron Microscopy for species characterization. According to the PCA, several of the Paludomus species clustered together (P. chilinoides and P. sulcatus together and P. bicinctus and P. decussatus), indicating that shell morphometry is not a reliable characteristic for species separation and identification. However, especially the pattern and shape of the cusps of the median teeth in the radulae varied and was unique to each of the species. Hence, the radulae teeth pattern can be used as a reliable character for identifying closely related Paludomus species.
Effect of bisphenol a on growth-related outcomes and survival of early life stages of polypedates cruciger
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Rajapaksha, R.M.H.N.; Dissanayaka, P.; Rajapaksha, R.P.G.K.
Bisphenol A is a widely used chemical in the plastic industry worldwide. Urban water sources are frequently polluted by bisphenol A leaching from plastic waste and industrial effluents, hence threatening aquatic species. Bisphenol A is an endocrine disruptor that perturbs natural hormone signalling pathways affecting living organisms' growth, development, and physiology. This study assessed the impact of long- term exposure to Bisphenol A on the early life stages of Polypedates cruciger (Common hourglass tree frog). Twenty tadpoles of Gosner stage 26 – 27 were assigned to triplicate tanks treated with environmentally relevant concentrations of bisphenol A (1, 10, 100 μg/l) and treatment control (1% v/v ethanol) for 80 days. The total body length, tail length, and body weight of tadpoles were observed weekly. The survival rate, tail length ratio and increments in body weight and length were calculated at the end of the treatment. The total body length of tadpoles increased with increasing concentrations of bisphenol A. Total body lengths of tadpoles in all bisphenol A treatments were significantly higher than those in control (p<0.05). The mean tail length ratio gradually increased with increasing concentrations of bisphenol A. Tail length ratio of those in control and 1 μg/l bisphenol A was significantly lower than those exposed to higher exposures (p<0.05). Body weight increment was not significantly different between treatment and controls (p>0.05). About 90% of all tadpoles survived in treatments and control, with no significant differences in survival between treatments and control (p>0.05). Accordingly, it can be concluded that environmentally relevant concentrations of bisphenol A do not affect survival but has significant negative impacts on growth-related parameters in Polypedates cruciger.
Application of purified and modified - pyrolytic carbon char in rubber compounding
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) De Zoysa, D.M.D.A.; Sudusinghe, Y.C.Y.; Hewage, J.S.; Ranaweera, A.S.
The waste tire pyrolysis process has attracted considerable interest as a sustainable solution to manage the accumulation of waste tires worldwide. The process produces three main fractions: gas, liquid and solid. The gaseous and liquid fractions are useful in industry as fuels; however, the solid fraction rich in carbon black has no use in Sri Lanka due to the presence of many impurities. The present study describes an efficient and economical route to purify contaminated pyrolytic char to manufacture value-added products. The pyrolytic carbon char was first passed through a 200 μm mesh to separate small particles, followed by size reduction by ball milling. These particles were demineralized stepwise using dilute HCl acid and NaOH at 60 °C for 1.0 h. Treated and untreated samples were characterized by carbon, hydrogen and nitrogen analysis, X-Ray Diffraction analysis and iodine adsorption experiments. The purified carbon black samples were used as reinforcing fillers for preparing rubber compounds according to the American Chemical Society 1 (ACS 1) formula. The physicomechanical properties of rubber compounds of purified carbon black prepared were consistent with compounds prepared with commercial carbon black, N660 and N330. CHN analysis shows that crude pyrolytic char (C-PT) contains 69% carbon, which can be improved up to 90% after washing with 2 M HCl twice and 2 M NaOH once. The iodine number of the sample was improved after demineralization (C-PT 180 mg/g and demineralized sample have 215 mg/g and 188 mg/g, 240 mg/g N660 and N330). There is no significant difference between the abrasion, tensile, tear, and compression properties of controls and ball-milled-treated samples. The average of all compound hardness is similar to the controls. The efficiency and value of the purification protocol in the current study were confirmed by test results and showed high potential application in the industry.
Antibacterial activity of different plant extracts and their combinations with turmeric extract against staphylococcus aureus strains
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Silva, M.C.G.; Uduwela, D.R.; Jayasinghe, J.M.S.; Gunathilake, W.S.S.; Liyanapathirana, L.V.C.; Ekanayake, E.W.M.A.; Dissanayake, U.P.R.U.; Wickramasinghe, A.
Drug resistance in bacteria has become a major concern in pharmaceutical research. Natural products have high structural diversity and potent antibacterial activity (AA). Hence, they can be a good source for antibacterial drug development. This study aimed to investigate the AA of Coffea arabica (Coffee- CF) leaves, Murraya koenigii leaves (Curry leaves- CL), Tabernaemontana dichotoma (Poison nut- PN) leaves and Curcuma longa (Turmeric-TR) rhizomes and their combinations. The crude extracts were prepared using dried, powdered plant parts where the leaves were extracted into water-acetone (v/v 1:1), and TR rhizomes were extracted into methanol-acetone (v/v 1:1) using a bottle shaker. The individual extracts and the nine combinations of three plant extracts with TR extract in 1:3, 1:1 and 3:1 ratios were assessed for AA by broth microdilution assay against five Staphylococcus aureus bacterial strains as they are involved in wound infections. Among the four individual extracts, TR showed the lowest Minimum Inhibitory Concentration (MIC) of 98 mg/l, for all five bacterial strains and the lowest Minimum Bactericidal Concentration (MBC) values ranging from 195 - 390 mg/l resulting in the highest AA. CL, CF and PN showed MICs ranging from 780 - 1,560 mg/l, 1560 - 3,125 mg/l and 780 - 6,250 mg/l, respectively and MBCs ranging from 1,560 - 6,250 mg/l, 6,250 - 12,500 mg/l and 1,560 - 12,500 mg/l, respectively. From the nine combinations, CL/TR with 3:1 ratio showed the highest AA (MIC- 48 mg/l, MBC- 98 mg/l). However, in CF/TR and PN/TR, 1:3 ratio showed the majority of low MIC and MBC values against the five bacterial strains. An enhanced AA for the three leaf extracts was observed when combined with TR extract. Amongst the four individual extracts and the nine combinations, CL/TR 3:1 combination exhibited the highest antibacterial properties. Though TR shows the highest AA among individual extracts, it increased the overall AA when present in the mixture of CL/TR in 3:1 ratio. The results revealed that using these plant extracts in combination with TR enhances the AA more than using them as individual plant extracts.