Browsing by Author "Wickramaarachchi, S."

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A new bioactive curvularin macrolide from an endolichenic fungus, Curvularia trifolii, isolated from Usnea sp., in Sri Lanka
(Book of Abstracts, Annual Research Symposium 2014, 2014) Samanthi, K.A.U.; Wickramaarachchi, S.; Wijeratne, E.M.; Paranagama, P.A.
The search for new bioactive natural products is still the main way of discovering new drug leads. Although fungi are well-known producers of secondary metabolites with new structurally diverse bioactive compounds, isolation of bioactive compounds from endolichenic fungi still remain underexplored as potential source of natural products. Endolichenic fungi are microorganisms living in the thalli of lichens that are analogous to the plant endophytic fungi inhabiting the intercellular spaces of the host. Curvularia trifolii was isolated from the lichen, Usnea sp., available in Hakgala botanical garden, Sri Lanka. Identification of the fungus was confirmed using morphological characters followed by the molecular identification (DNA sequencing). Invitro large scale cultures of C.trifolii were prepared in 60 large Petri dishes containing potato dextrose agar medium and after 10 days secondary metabolites were extracted into ethyl acetate. The crude extract was tested using two types of bio assays, for the investigation of antioxidant and anti-inflammatory activities. Antioxidant activity of the crude ethyl acetate extract was explored by carrying out DPPH free radical scavenging assay and Anti-inflammatory activity was evaluated using Human Red Blood Cell Membrane Stability (HRBC) assay. Since the crude extract showed high activity in both the assays, it was partitioned into hexane, chloroform (CHCl3) and 60% aq.MeOH and identified the bioactive fractions. The activity of CHCl3 fraction was confirmed and it was further fractionated using bioassay guided column chromatography (silica, sephadex) and preparative TLC to isolate pure compounds. One florescent active pure bioactive compound (C23H30O6) was isolated from the CHCl3 fraction and identified as using 1D, 2D NMR, MS, IR and UV spectral data. The structure of new compound was thus established as 5-methoxy-4,8,15-trimethyl-3,7-dioxo-1,3,7,8,9,10,11,12,13,14,15,15?-dodecahydrocyclododeca[de]isochromene-15-carboxylic acid and the bioassay results revealed that it is a new curvularin macrolide with IC50 values, 68.6�4.3 ?g/mL and 310�48.2 ?g/mL for DPPH antioxidant assay and anti-inflammatory assay respectively. Hence it is revealed that derivative isolated from C. trifolii can be developed as an important antioxidant and anti-inflammatory drug.
Bioactive properties of Rambutan (Nephelium lappaceum L.) and Durian (Durio zibethinus Murr.) peel extracts
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Silva, A.G.; Wickramaarachchi, S.; Attanayake, R. N.; Rajapakse, C. S. K.
Although these fruits are seasonal, a considerable amount of Rambutan (Nephelium lappaceum L.) and Durian (Durio zibethinus Murr.) fruit residues (mainly peels) are collected each year as waste materials, due to the significant volume of trade of these fruits. Therefore, present work was initiated with the aim of evaluating the impact of these residues lying as waste and possible re-use, by investigating the bioactive properties in peels of rambutan and durian. Methanol extracts of Rambutan and Durian peels were sequentially extracted with hexane, chloroform and methanol. First, methanol extracts of peels were subjected to phytochemical screening following standard procedures and results revealed that rambutan and durian peels were rich in polyphenols, flavonoids, steroids, coumarin, etc. Total phenolic content (TPC) and total flavonoid content (TFC) of methanol extracts of peels were determined using Folin-Ciocalteu and aluminium chloride method, respectively. Results showed that TPC and TFC in methanol extract of durian peels were (11.39 ± 0.49 mg GAE/g dry weight, 257.20 ± 5.14 mg Catechin /g dry weight) higher than those of Rambutan peels (2.73 ± 0.15 mg GAE/g dry weight, 198.00 ± 1.89 mg Catechin /g dry weight). Further, the antioxidant activity of methanol extracts of peels and its fractions were investigated using 1, 1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging assay and the correlation with their TPC and TFC were examined using Pearson’s correlation analysis. The strongest antioxidant activity was observed in hexane fraction of Rambutan peels with IC50 value of 13.49 ± 0.52 μg/mL, and which was lower than that of the control, butylated hydroxytoluene (43.70 ± 0.89 μg/mL). Significant positive correlations were observed between TPC and TFC in fractions of rambutan and durian peels with their DPPH radical scavenging activity indicating that phenolics and flavonoids in rambutan and durian peels may contribute to their strong antioxidant activities. The antimicrobial activity of the extracts of peels and its fractions were assessed by using disc diffusion method against a bacterial species of Staphylococcus aureus and fungal species, Fusarium oxyporum and Aspergillus flavus. The lowest concentration of methanolic extract of durian and rambutan peels that showed an inhibition against Staphylococcus aureus was 31.25 μg/mL. It was also found out that neither peels of rambutan nor durian had antifungal activity against the two selected fungal species. Results revealed that the peels of rambutan and durian are potential sources of antioxidants and antibacterial agents
Discovering new bioactive molecules from endolichenic fungi, Curvularia trifolii and Penicillium Citrinum
(2015) Paranagama, P.A.; Upamalika, S.; Wickramaarachchi, S.; Wijeratne, K.M.
Endolichenic fungi are microorganisms living in the thalli of lichens that are analogous to the plant endophytic species inhabiting the intercellular spaces of the hosts. The diversity and prevalence of endolichenic fungi have not been studied extensively and there are only a few recorded studies on isolations and identifications of endolichenic fungi. The endolichenic fungi available in Sri Lanka are still an untapped source of bioactive natural products since their identity and the chemistry of their secondary metabolites have not been explored thoroughly. In our ongoing research programme on searching for new bioactive compounds from endolichenic fungi, we have investigated an endolichenic fungi, Curvularia trifolii and Penicillium citrinum isolated from the lichens, Usnea sp. and Parmotreama sp. collected in the Hakgala Botanical Garden, Sri Lanka. Ethyl acetate extracts of two endolichenic fungi, C. trifolii and P. citrinum led to isolation of four new compounds, 1- 4. The structures of the new compounds were determined on the basis of their 1D NMR, 2D NMR and FABMS spectroscopic data. The new compounds, 1 - 4 showed radical scavenging activities with IC50 values of 4.0±2.6 mg/mL, 1.3±0.2 mg/mL, 159.7±22.3 μg/mL and 68.6±4.3 μg/mL respectively in DPPH antioxidant assay and antioxidant activity of the compound 2 was comparable to the standard antioxidant compound, BHT. Moreover, the new compound, 2 were evaluated for their antiinflammatory activity and exhibited significant activity comparable to the standard antiinflammatory drug, Aspirin. The Compound 1 was evaluated for inhibition of cell proliferation in a panel of five cancer cell lines NCI-H460, MCF-7, SF-268, PC-3M, and MIA Pa Ca-2 and exhibited >90% inhibitory activity at 5 μg/mL with all the above cell lines.
New Bioactive poliketide from endolichenic fungus, Curvularia trifolii, inhabiting the lichen, Usnea sp. collected from Haggala Botanical Garden
(Faculty of Graduate Studies, University of Kelaniya, 2015) Samanthi, K.A.U.; Wickramaarachchi, S.; Wijerathne, E.M.K.; Paranagama, P.A.
Endolichenic fungi (ELF), which live in healthy tissues of lichens, are one of the promising producers of structurally diverse novel bioactive secondary metabolites. It has been reported that endolichenic fungi are rich sources for the discovery of new compounds with significant medicinal values and this was demonstrated by isolation and identification of new anticancer, antifungal, antibacterial and antioxidant agents from endolichenic fungal extracts. In Sri Lanka, research group of University of Kelaniya initiated a research program on ELF and have isolated few interesting bioactive poliketides from ELF of three lichen species available in Sri Lanka. They have shown great potential to be a source for novel bioactive natural products. The objectives of this study were isolation and identification of bioactive compounds of the endolichenic fungus, Curvularia trifolii isolated from the lichen Usnea species. In a continuation of our chemical investigations in search of secondary metabolites of endolichenic fungi with medicinal value led to the isolation of few bioactive compounds. In this present study, C. trifolii was grown in large scale and incubated at room temperature for 10 days. The metabolites were extracted into ethyl acetate (EtOAc). Antibacterial, anticancer and insecticidal activities of the EtOAc extract were evaluated using in-vitro bioassays. The EtOAc extract was subjected to a silica gel column chromatography resulting, one major compound with high bioactivities. The isolated pure white crystalline compound was identified as 1,14-dihydroxy-6-methyl-6,7,8,9,10,10,14,14 -octahydro-1H-benzo[f][1] oxacyclododecin-4(13H)-one using 1H, 13C NMR, 2D NMR and MS data. The compound was found to possess antibacterial activity against three test pathogens, anticancer activity at (NCIH-460), (MCF-7), (SF-268), (PC3M), and (MDA-MB-231) cell lines and insecticidal activity.
Two new antioxidant active polyketides from Penicillium citrinum, an endolichenic fungus isolated from Parmotrema species in Sri Lanka
(National Science Foundation of Sri Lanka, 2015) Samanthi, K.A.U.; Wickramaarachchi, S.; Wijeratne, E.M.K.; Paranagama, P.A.
Bioassay guided fractionation of the ethyl acetate extract of a laboratory culture of Penicillium citrinum, an endolichenic fungal strain isolated from a Parmotrema species in Sri Lanka, led to the isolation of two new fungal polyketides (1 and 2). The structures of these compounds were determined on the basis of their 1D NMR, 2D NMR and FABMS spectroscopic data. The two compounds (1 and 2) showed radical scavenging activity with IC50 values of 159.7 ± 22.3 μg/mL and 68.6 ± 4.3 μg/mL, respectively in DPPH antioxidant assay. The antioxidant activity of compound 2 was comparable to the standard antioxidant compound butylated hydroxytoluene (BHT).