Browsing by Author "Karunaratne, V."

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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.
Determination of antibacterial activity of 6β-hydroxybetunolic acid and interaction with oxacillin
(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Wickramasingha, W. G. D.; Jayasinghe, S.; Karunaratne, D. N.; Liyanapathirana, V.; Ekanayake, A.; Karunaratne, V.
Various strides have been undertaken with successful results in the treatment and cure of significant number of bacterial infections. However, many bacteria are becoming resistant to some of the prevailing drugs due to either the misuse or the prolonged use of the available antibiotics increasing the necessity for discovering new antibiotics to combat resistant microorganisms. Plants and their secondary metabolites can be considered as good sources of scaffolds to provide structurally diverse bioactive compounds as potential therapeutic agents and combination of them with standard antibiotic to obtain synergistic effect. The objective of this study was to determine the antibacterial activity of one of a lupeol type triterpenoid (6β-hydroxybetunolic acid) isolated from the bark of Schumacheria castaneifolia Vahl. which is an endemic plant to Sri Lanka and to determine the synergistic effect with Oxacillin. Antimicrobial activity of 6β-hydroxybetunolic acid was evaluated utilizing micro broth dilution assay in 96 well plates against two standard strains of Staphylococcus aureus, 4 strains of clinically isolated Methicillin resistant S. aureus, standard strains of Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, carbepenemas producing Kebsiella pneumonia and carbepenemas non-producing Kebsiella pneumonia and four strains of clinically isolated Acinetobacter sp. Synergistic effect of the combination of 6β-hydroxybetunolic acid and Oxacillin was tested against Standard strain of S. aureus and MRSA using checker board method. Results revealed that 6β-hydroxybetunolic acid shows significant antibacterial activity only against the Gram positive strains; MIC values of S. aureus (ATCC 29213), S. aureus (ATCC 29213), E. faecalis (ATCC 29212) and four MRSA strains were 32, 16, 32, 32, 32, 32, 16 ppm respectively. However MIC value of Oxacilin against S. aureus (ATCC 29213) was 0.25 ppm. 6β-hydroxybetunolic acid has synergistic effect with Oxacillin against S. aureus and additive effect against all the tested MRSA. These results concluded that the antibacterial activity of 6β-hydroxybetunolic acid is predominantly depending on the cell wall difference of the bacteria.
Encapsulation of essential oil blend in β-CD nanoparticles as a repellent for slow release
(Moleclar Medicine Unit, Faculty of Medicine, University of Kelaniya, Sri Lanka, 2015) Jayaweera, V.; Eliyapura, A.; Gunasekara, D.; Weerasinghe, L.; Gunathilaka, P.A.D.H.N.; Abeyewickreme, W.; Karunaratne, V.
BACKGROUND: Malaria, dengue, and other tropical diseases carried by arthropods such as mosquitoes, ticks and fleas have greatly affected life expectancy, infant mortality, quality of life and work productivity. Essential oils such as citronella, lemon eucalyptus, peppermint, lemon, eucalyptus, lemongrass, geranium, and lavender are known for their mosquito repellency. Due to high volatility of essential oils, these are needed to be reapplied to the skin every 30–60 minutes. Therefore, development of a long lasting mosquito repellent is needed for effective repellent activity. The aim of this experiment is to develop a new blend which encompasses citronella, lemon eucalyptus, lemon and lavender. This oil blend is encapsulated using β-Cyclodextrin (β-CD) to decrease the volatility of the oil blend and increases the long-lasting repellency. METHODS: Citronella, lemon eucalyptus, lemon and lavender were obtained in 15% v/v, 15% v/v, 1% v/v and 1% v/v respectively for a total volume of 100 ml. These oils were mixed with 0.2% w/v of β-Cyclodextrin for encapsulation. The blend was sonicated for 20 min and dissolved in ethanol. This final encapsulated mixture was subjected to bioassays using 110 adult Aedes albopictus mosquitoes against the control. Sitting and biting mosquito behavior patterns were studied against the releasing time. RESULTS: The bioassay results indicated that the encapsulated repellent product is effective against the mosquitos up to 6 hours with zero sitting and biting comparatively to the control. In the 7th hour showed single mosquito sitting with zero biting. CONCLUSION: The encapsulated repellent is effective against the Ae, albopictus mosquitoes for 6 hour time period. Therefore, it is a long-lasting repellent that protect against dengue fever caused by mosquitoes.
Investigation of antihyperglycaemic activity of hexane extract of polyherbal mixture in streptozotocin induced diabetic rats
(Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Sampath, S.N.T.I.; Jayasinghe, J.M.S.; Attanayake, A.P.; Karunaratne, V.
A homemade Ayurvedic remedy made of cloves of Allium sativum, leaves of Murraya koenigii, seeds of Piper nigrum and dried fruit rinds of Garcinia quaesita is considered as an antidiabetic polyherbal mixture. This polyherbal mixture has been used for the treatment of diabetes mellitus and dyslipidaemia in Sri Lankan traditional medicine. The in-vitro antioxidant and in-vivo acute antihyperglycaemic screening of hexane, ethyl acetate and methanol extracts of the above polyherbal mixture were studied and the hexane extract showed a significant antioxidant and dose dependent antihyperglycaemic activity when compared with the two extracts. Hence, the present study was aimed to further investigate the effect of administration of the hexane extract of polyherbal mixture at the optimum effective therapeutic dose for 30 days on serum glycaemic parameters in streptozotocin induced diabetic rats. Diabetes was induced in male Wistar rats by injecting with streptozotocin at the single dose of 65 mgkg-1 . Group one and two considered as the healthy untreated control, diabetic untreated control rats and received standard animal food and distilled water daily for 30 days (n = 6 /group). Group three and four were diabetic rats and were treated with the hexane extract (25 mgkg-1 ) and glibenclamide (positive control - 0.5 mgkg1 ) daily for 30 days respectively (n = 6 /group). Body weight of treated and control group rats were measured on 1 st, 7th, 14th, 21st and 28th day of the experiment. On the 30th day, all experimental rats were euthanized and blood was collected by cardiac puncture. The antihyperglycaemic activity was evaluated by determining the changes of fasting serum glucose concentration in each group using oral glucose tolerance test on 1 st , 7 th, 14th, 21st and 28th day and analyzed through total oral glucose tolerance curve (TAUC) values. Further, the percentage of glycated haemoglobin (HbA1C) and fasting serum glucose concentration were determined as glycaemic parameters in each group. The body weight was increased in healthy untreated control group and treated groups while the diabetic untreated control group showed a 10% reduction of body weight during the intervention period, indicating the treatment led to control loss of body weight. The oral administration of hexane extract and glibenclamde, lowered the TAUC values by 21% and 35% respectively and these values were statistically significant compared with TAUC value of diabetic untreated group (p < 0.05) on the 28th day of experiment. There was a statistically significant reduction in the HbA1C (27%, 33%) and the fasting serum glucose concentration (23%, 33%) in hexane extract and glibenclamide treated diabetic rats when compared to streptozotocin induced untreated diabetic rats (p < 0.05). The findings of the current study revealed that the hexane extract of the polyherbal mixture is a potential source to develop antidiabetic agent/s and further investigations are warranted to study the cellular antidiabetic mechanisms.