Browsing by Author "Attanayake, A. P."

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Alpha-amylase and alpha-glucosidase inhibitory activities of a novel compound isolated from Murraya koenigii
(Faculty of Science, University of Kelaniya Sri Lanka, 2022) Sampath, S. N. T. I.; Jayasinghe, J. M. S.; Attanayake, A. P.; Karunaratne, V.
Herbal plants are composed of a vast amount of novel antidiabetic drugs for the management of diabetes mellitus. The leaves of Murraya koenigii L. Sprengel. which belongs to Family- Rutaceae (Common name- curry leaves) plant is known to be a promising source of natural bioactive compounds. In this research, we report the isolation and characterization of a new compound from hexane extract of leaves of M. koenigii and its in vitro antidiabetic activity. The new compound was identified as 3,3',5,5',8-pentamethyl-3,3'-bis (4-methylpent-3-en-1-yl)-3,3',11,11'-tetrahydro-10,10'-bipyrano [3,2-a] carbazole and the structure was elucidated based on extensive 13C and 1H NMR, high-resolution mass spectrometry (HRMS) and 2D NMR analysis. Investigated the in vitro antidiabetic activity of the new dimer using alpha-amylase and alpha-glucosidase enzyme inhibition activities. The compound exhibited significant alpha-amylase activity (IC50 = 30.32 ±0.34 ppm) and the alpha-glucosidase inhibition activity (IC50 = 30.91 ±0.36 ppm) when compared with the acarbose at 0.05 significant level. These results revealed that the new compound isolated from the hexane extract of leaves of M. koenigii could act as an antidiabetic agent.
Effect of a herbal capsule of Coccinia grandis (L.) Voigt (Cucurbitaceae) on lipid profile in patients with newly diagnosed type 2 diabetes mellitus
(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Wasana, K. G. P.; Attanayake, A. P.; Weerarathna, T. P.; Jayatilaka, K. A. P. W.
Herbal antidiabetic agents have been popular among general population due to their historical usage along with the exceptional therapeutic efficacy. The present study was aimed to determine the effect of a newly developed herbal capsule of C. grandis, which consists of freeze dried powder of the hot water extract of C. grandis leaves, on lipid profile in patients with newly diagnosed type 2 diabetes mellitus (T2DM). Three months long, placebo controlled, double blind, randomized clinical trial was conducted involving 147 individuals with newly diagnosed T2DM. Patients with known renal, liver, cardiac, respiratory, thyroid, psychiatric and any other chronic or acute diseases, and pregnant women were excluded. Individuals are using antilipidaemic drugs were also excluded. Selected individuals were randomly allocated into two groups of test and control. The test group received newly developed herbal capsule of C. grandis (500 mg) and the control group received placebo capsule (500 mg) once daily for three months. Serum lipid profile consisting of total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), triglyceride (TG) and very low density lipoprotein cholesterol (VLDL-C) was estimated at the base line (week=0) and at the end of intervention (week=12). Independent sample t-test was used to compare the two groups. A percentage reductions of TC, LDL-C, TG and VLDL-C were 2.12%, 3.51%, 27.36% and 27.36% respectively and increment of HDL-C (1.92%) was observed in herbal capsule treated group. The results of the t- test revealed that TG (p=0.003) and VLDL-C (p=0.003) are significantly decreased in the herbal capsule treated group. There were no statistically significant changes (p>0.05) in TC, HDL-C and LDL-C between two groups. In conclusion, 500 mg of herbal capsule of C. grandis is beneficial in reducing elevated TG and VLDL-C in lipid profile of patients with newly diagnosed T2DM.
Identification of plant based anti-diabetic drug leads: A computer-based drug discovery approach
(Department of Social Statistics, Faculty of Social Sciences, University of Kelaniya Sri Lanka, 2023) Katipearachchi, S. H.; Faizan, M.; Kalansuriya, P.; Attanayake, A. P.
Diabetes mellitus is known to be one of the fastest-rising chronic metabolic diseases with multiple etiologies. The disease is characterized by chronic hyperglycemia resulting from defects in insulin secretion, insulin action or both. Available therapeutic agents, come with their fair share of side effects. Plant-derived medications that have been used for centuries in the treatment of diabetes in ayurveda and folk medicine have gained a lot of attention in recent years. Studies have shown that plants consist of many bioactive compounds with anti-diabetic properties. Computer-aided drug discovery is slowly gaining popularity with molecular docking accelerating drug discovery by providing structure-based interactions between ligand and receptor proteins. This study was designed to use computational methods to identify the best anti-diabetic compounds devised from ten selected plants. A total of ten plants and three target receptor proteins were selected for in silico screening based on the literature. The selected plants were Nigella sativa L., Coccinia grandis (L.) Voigt, Cheilocostus speciosus (J.Koenig) C.D.Specht, Momordica charantia L., Strychnos potatorum L.f, Gymnema sylvestre (Retz.) R.Br., Aloe vera (L.) Burm.f., Scoparia dulcis L., Abutilon indicum (L.) Sweet, and Trigonella foenum-graceum L. A phytochemical compound library with a total of 952 ligands was prepared using IMPPAT database. The main target receptor proteins, include 􀁄-glucosidase, 􀁄-amylase and dipeptidyl peptidase-IV (DPP-IV), based on their key roles in the maintenance of glucose homeostasis. The 3D protein structures were downloaded from the RCSB Protein Data Bank. Miglitol, sitagliptin and acarbose were selected as reference drugs for each target protein to conduct a comparative study. Biovia Discovery Studio was used to visualize the target protein and prepare the protein for virtual screening. UCSF Chimera and PyRx Autodock were used for the energy minimization of the proteins and the virtual screening respectively. Schrodinger Maestro was used for the dynamic simulation studies with the OPLS- 2005 force field and TIP3P Solvent model. The compound library was screened by carrying out flexible docking against each target protein. The search space for virtual screening was defined to include all the critical inhibitor-binding sites based on the literature. All the compounds having binding affinity less than -6 kcal/mol were selected.. Only the compounds with promising binding energy values, depending on each target, were subjected to the target-ligand interaction analysis conducted using Biovia Discovery Studio. The binding affinity and interaction patterns of phytochemical ligands were evaluated against three receptor proteins. The best three molecules for each protein were selected based on the best hydrogen bond interactions since they determine the specific, energetically favorable ligand binding at the target sites. The selected 12 molecules were further analyzed for the best target-ligand binding conformation and subjected to molecular dynamics simulation. Compound 27 and compound 85 in T. foenum-graceum with RMSD less than 3Å and hydrogen bond retention above 75% in 100NS simulation were identified as promising therapeutic drug leads for the treatment of diabetes. In vitro screening for the antidiabetic activities would be conducted using 􀁄-glucosidase, 􀁄-amylase and DPP-IV assays to further assess their effectiveness as anti-diabetic drug leads.
In vitro antidiabetic activity of fractionated extracts of Coccinia grandis (L.) Voigt
(Faculty of Science, University of Kelaniya, Sri Lanka, 2021) Wasana, K. G. P.; Attanayake, A. P.; Jayasinghe, J. M. S.; Weeraratna, T. P.; Jayatilaka, K. A. P. W.
The Paspanguwa herbal formulation is commonly consumed as a traditional medicine in Sri Lanka. Paspanguwa consists of five ingredients, namely the rhizome of Zingiber officinale (Inguru), leaves and stem of Hedyotis corymbosa (Pathpadagam), dried berries of Solanum xanthocarpum (Katuwalbatu), dried stem of Coscinium fenestratum (Venivalgata), and dried seeds of Coriandrum sativum (Koththamalli). The importance and objective of this study was to prove the antioxidant and anti-inflammatory properties of traditionally used decotion, Paspanguwa claimed to have. In the present study, water extracts of the individual ingredient and the Paspanguwa decoction were screened for their total soluble phenolic content (TPC), total soluble flavonoid content (TFC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, and their ability to inhibit protein denaturation (anti-inflammatory activity). The highest and the lowest TPC was seen in Coriander and ginger as 12.76 ± 1.00 and 7.89 ± 0.86 mg Gallic acid equivalent/g dry weight, respectively. The highest and the lowest TFC was seen in Katuwalbatu and Pathpadagam as 778.19 ± 1.40 and 282.14 ± 1.49 µg Catechin equivalent/g of dry weight, respectively. The lowest and the highest IC50 values for the DPPH assay was seen in Paspanguwa decoction and Katuwalbatu as 253.4 ± 8.2 and 609.7 ± 5.6 µg/mL, respectively, while the standard ascorbic acid showed 111.0 ± 6.1 µg/mL. The highest and lowest reducing power percentages were seen in Paspanguwa decoction and coriander as 94.74 ± 1.31 and 22.95 ± 0.96 while the standard ascorbic acid showed 109.89 ± 0.96. The ability to inhibit protein denaturation varied in the order of: Acetylsalicylic acid (standard) > Paspanguwa decoction > ginger > coriander > Venivalgata > Katuwalbatu > Pathpadagam at all the three concentrations (625, 1250, and 2500 µg/mL). These results suggest that Paspanguwa water extract is a good source of antioxidants with TFC and TPC with a higher ability to inhibit protein denaturation. Our findings corroborate with the previous in vitro studies of the antioxidant activity of Paspanguwa. However, our study is the first to reveal the anti-inflammatory action, total flavonoid content, and reducing power of the Paspanguwa herbal formula. Further, this study validated the use of Paspanguwa as a good source of antioxidants together with anti-inflammatory activity in traditional Ayurvedic medicine.
In vitro antidiabetic activity of Spondias pinnata aqueous extract and encapsulated chitosan-TPP nanoparticles
(Faculty of Science, University of Kelaniya, Sri Lanka., 2021) Wadasinghe, R. R.; Attanayake, A. P.; Kalansuriya, P.
Spondias pinnata (L. f.) Kurz is a medicinal plant used in complementary medicine. Decoctions prepared using stem-bark of S. pinnata find applications in treating diabetes mellitus. However, low bioavailability of bioactive metabolites (polyphenols and flavonoids) and lack of appropriate release of metabolites delimit the antidiabetic activity of S. pinnata aqueous extract (SAE). Encapsulation of SAE with chitosan-tripolyphosphate (CS-TPP) could enhance its therapeutic potential and provide controlled release. The objective of this work to determine in vitro antidiabetic activity of S. pinnata stem-bark extracts and SAE-encapsulated CS-TPP nanoparticles using α-amylase inhibitory, α-glucosidase inhibitory, glucose uptake and glucose adsorption assay. The extracts were prepared by extracting dried and powdered stem-bark of S. pinnata into distilled water, acetone, ethyl acetate, dichloromethane under ultrasonication (40 kHz, 37 °C, 30 min) separately. The total phenol content (TPC) and flavonoid content (TFC) of the extracts were determined using Folin-Ciocalteu and aluminium chloride methods, respectively. Based on the results of α-amylase inhibitory assay, SAE was selected for the encapsulation with CS-TPP. The SAE had TPC of 4.18±0.02 mg gallic acid equivalents per gram of dry weight (GAE/g DW) and TFC of 0.37±0.01 mg quercetin equivalents per gram of dry weight (QE/g DW) and showed the highest α-amylase inhibitory activity (IC50 53.34±7.43 µg/mL). The acetone extract had TPC of 34.43±0.35 mg GAE/g DW and TFC of 4.06±0.05 mg QE/g DW and showed the highest α-glucosidase inhibitory activity (IC50 8.82±1.42 µg/mL). The highest glucose uptake and glucose adsorption were shown by acetone extract and aqueous extract, respectively. SAE-encapsulated nanoparticles were prepared from CS-TPP at varying concentrations (0.250, 0.375, 0.500 and 0.625% w/v) of SAE using ionic gelation method under magnetic stirring; the highest encapsulation efficiency (68.21% ± 0.66%) and loading capacity (0.79% ± 0.17%) were obtained at 0.625% w/v of SAE. Loaded nanoparticles were separated by centrifugation and free polyphenols were determined by Folin-Ciocalteu method. The Z-average particle diameter of SAE-encapsulated CS-TPP nanoformulations was 417±86 nm with polydispersity index of 0.574 and zeta potential of +20.63 mV. The IC50 values corresponding to α-amylase inhibitory activity and α-glucosidase inhibitory activity of SAE-encapsulated CS-TPP nanoparticles were 1.10±0.03 mg/mL and 3.16±0.15 mg/mL, respectively. Although the percentage of glucose uptake and adsorption in SAE encapsulated CS-TPP nanoparticles is lower than the crude extract, it had shown 11.59±1.03 % glucose uptake at 5 mM glucose concentration and 1.47 mmol/g glucose adsorption at 100 mM glucose concentration. The SAE, acetone extract and SAE-encapsulated CS-TPP nanoparticles showed higher antidiabetic activity than the positive control, acarbose. Further investigations on the releasing profiles of SAE-encapsulated CS-TPP nanoparticles would reveal the rates at which the active metabolites are released to the media during the timeframes of the conducted assays.
Nitric oxide radical scavenging potential of selected widely used spices and in a mixture of spices
(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Wickramaratna, H. D. P.; Amarasiri, A. M. S. S.; Attanayake, A. P.
A remarkable research interest has been shown on phytochemicals in spices and their bioactivities during the last decade. Nitric oxide (NO) radical scavenging potential is one of the assays used in the determination of in vitro antioxidant activity. The study aims to determine NO radical scavenging potential of the aqueous extracts of ten selected Sri Lankan spices and a mixture of spices made from five selected spices with high NO scavenging potential. The spices were randomly collected within the areas of Sabaragamuwa and Southern provinces from their natural habitats. L-ascorbic acid was used as the reference compound in the assay. The NO radical scavenging potential were estimated following the standard protocol using a spectrophotometric assay. The half maximal inhibitory concentration (IC50) was calculated using regression analysis and the values were expressed as mean ± standard deviation (SD) of the three analytical triplicates. IC50 values of the selected spices were 269.33 ± 2.21 μg/mL (Piper nigrum), 270.24 ± 4.23 μg/mL (Curcuma domestica), 279.85 ± 1.62 μg/ mL (Elettaria repens), 288.88 ± 0.87 μg/mL (Myristica fragrans), 292.59 ± 11.83 μg/mL (Zingiber officinale), 322.05 ± 2.13 μg/mL (Eugenia caryophyllata), 341.11 ± 1.39 μg/mL (Cinnamomum verum), 355.94 ± 2.98 μg/mL (Cymbopogon citratus), 356.32 ± 1.31 μg/mL (Brassica integrifolia) and 394.19 ± 3.87 μg/mL (Capsicum frutescens). There was a statistically significant difference in between ten spices (p<0.05). The spices which showed the highest NO radical scavenging potential (lowest IC50) were selected for the mixture. Accordingly, P. nigrum, C. domestica, E. repens, M. fragrans and Z. officinale were selected. The mixture showed the highest NO radical scavenging potential with the lowest value of IC50 (256.42 ± 0.22 μg/mL) compared to the individual spices. Based on the results, all selected extracts of spices possess NO scavenging potential and the mixture showed the highest activity.
Optimization of high-fat diet fed streptozotocin induced Wistar rat model for screening antidiabetic agents
(Faculty of Science, University of Kelaniya, Sri Lanka., 2021) Wickramasinghe, A. S. D.; Attanayake, A. P.; Kalansuriya, P.
High-fat diet (HFD) fed streptozotocin (STZ) induced Wistar rats are frequently used as animal models of type 2 diabetes mellitus for screening novel antidiabetic agents. As the composition of HFD, age and strain of rats, dose of STZ and the intended degree of pathophysiological changes vary among studies, the development of a model that best fits to a particular research setting is pivotal. Furthermore, ensuring the long-term stability and establishment of an adequate biochemical profile of the model are necessities which have been addressed by limited studies to date. This study attempted the development of a model which mimics type 2 diabetes mellitus for screening of novel antidiabetic drugs. Wistar rats were fed with a HFD (60% calories from fat) for four weeks, followed by STZ intraperitoneal injection (30, 40 and 50 mg/kg). Rats with fasting serum glucose >11.1 mmol/L were enrolled for the study. There were five groups (n=10/group); healthy rats, HFD fed rats, HFD+STZ (30 mg/kg) rats, HFD+STZ (40 mg/kg) rats, HFD+STZ (50 mg/kg) rats. The glycemic status of the rats was monitored weekly by the routine conduct of oral glucose tolerance tests. Experimental rats were euthanized after 28 days and blood samples were collected for biochemical investigations. Glycemic status of the model was assessed by determining fasting serum glucose, insulin, glycated hemoglobin (HbA1c) and homeostatic model assessment-insulin resistance (HOMA-IR). Lipid profiles were assessed by determining total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and very low-density lipoprotein cholesterol (VLDL-C) levels. STZ induced rats (30, 40 and 50 mg/kg) showed a significant dose dependent increase in fasting serum glucose (by 67, 61 and 136%) and insulin (by 19, 15 and 13%) concentrations (p<0.05). HOMA-IR was above 2.5 and increased in a dose dependent manner by 98, 108 and 176% in STZ induced rats (30, 40 and 50 mg/kg). However, only the STZ (50 mg/kg) induced group of rats showed fasting serum glucose concentration of 13.71 ± 1.01 (>11.1 mmol/L) and a significant increase in HbA1c by 66% compared to the healthy rats (p<0.05). Further, the STZ 50 mg/kg rats showed stable hyperglycemia throughout the study period. STZ induced rats (30, 40 and 50 mg/kg) also showed a significant dose dependent increase in TC (by 6, 7 and 9%), and TG (by 16, 15 and 23%) respectively (p<0.05). However, only the STZ induced (50 mg/kg) group of rats showed significant increase in serum concentrations of LDL-C (by 12%) and VLDL-C (by 16%) compared to the healthy rats (p<0.05). Only slight changes in HDL-C levels were observed in the STZ induced groups of rats however, the values were not significant (p>0.05). The results revealed that the Wistar rats fed with HFD rich in saturated fat for four weeks followed by a single intraperitoneal dose of STZ (50 mg/kg) would produce stable diabetic model which closely mimic pathophysiological features of type 2 DM characterized by insulin resistance and dyslipidemia.