Research activities of the Natural Product Project have been focused on the chemistry and bioactivity of secondary metabolites from plants, fungi (including endophytic fungi) and edible fruits of Sri Lanka. Another area of research has been the identification of polyphenols found in tea, fruits and edible spices using Liquid Chromatography – Mass Spectrometry (LC-MS). The overall objective of these projects is the identification bioactive extracts and compounds from natural sources, as potential resources for control of human and plant diseases.
The bioactivities of extracts and compounds are assessed using bioassays such as 2,2’-diphenyl-1picrylhydrazyl [DPPH] radical scavenging assay to detect the presence of natural antioxidants; the brine shrimp (Artemia salina) lethality assay to detect cytotoxicity lettuce (Lactuca sativa) seed germination assay to detect the presence of phytotoxic and allelopathic compounds and TLC bioautography method to detect the presence of antifungal compounds.
Naturally occurring enzyme inhibitors are important in the field of drug research and are biochemical tools that have potential utility in the treatment of diseases. These inhibitors interact with enzymes and block their activity towards their corresponding natural substrate. Inhibitors of -amylase, gluosidase, and lipase are drug targets for the treatments of diabetes, obesity and hyperlipidemia. Enzyme assays to detect the presence of naturally occurring -amylase, -glucosidase and lipase inhibitors respectively, are being used in the recognition of natural sources that may be of importance in the identification of extracts/compounds that can find application in the formulation of health and food related products. For example, -amylase, -glucosidase and lipase inhibitors are drug targets for the treatment of diabetes, obesity and hyperlipaemia, and may eventually be of use in drug research leading to the development of new therapeutic products. During 2014 the establishment of assays to detect the presence of inhibitors of urease and chymotrypsin enzymes is in progress.
The accidental discovery of the first antibiotic Penicillin from the mould Penicillium notatum led to the age of antibiotics and research on fungal metabolites. Some endophytic fungal strains produce natural products that are either identical or closely related to those produced by the host plant. Taxol, an anti-cancer drug obtained from the Pacific Yew tree Taxus brevifolia, was also produced by the endophytic fungus Taxomyces andreanae from the bark of T. brevifolia. Isolation of endophytic fungal strains from some Sri Lankan fruits (F. indica, Musa sp., seeds of Pouteria campechiana) and leaves of allelopathic plants has resulted in the isolation of some unusual bioactive metabolites. Compounds isolated from the leaves of Aspergillus niger included polyketide naphthopyrones rubrofurarin, foncesin, aurosperone, fonsecinone A and also ergosterol. Studies on metabolites produced by the Ambrosia fungus Monacrosporium ambrosium, ectosymbiotic fungus of the Shothole borer beetle (Xyleborus fornicatus) of tea, are in progress.
Tokyo Institute of Technology, Japan.
Mr. G.R.N. Rathnayaka
Ms. D. Thanabalasingham
Ms. D.M.D.M. Dissanayake
Mr. D.S. Jayaweera