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2.
Larsson, Josefin, et al.
(författare)
Expanding the ChemGPS chemical space with natural products
2005
Ingår i: Journal of natural products (Print). - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 68:7, s. 985-991
Tidskriftsartikel (refereegranskat) abstract
Recently various attempts have been made to increase the efficacy and precision of chemical libraries used in high-throughput screening (HTS) drug discovery approaches. One such approach is ChemGPS, which provides a defined chemical space for prescreening evaluation of chemical compound properties or virtual dereplication. In the present study, ChemGPS has been applied to a set of natural products shown to exhibit cyclooxygenase-1 and/or -2 (COX-1/2) inhibition. With the purpose of defining chemical properties and linking these to the observed mode of enzyme inhibition, this resulted in two lines of reasoning. On one hand several specific features of these compounds have been identified and discussed. Overall COX inhibition was frequently correlated with the presence of at least one ring in the structure, fragments exhibiting structural rigidity, and a relatively large molecular size. The concept "size" includes several parameters, e.g., molecular volume, weight, and number of bonds. On the other hand, and possibly even more important, was the unexpected finding that the natural products studied to a large extent fell outside the defined ChemGPS chemical space. Therefore, we also propose an expanded space for natural products: ChemGPS-NP.
3.
Lindholm, Petra, 1973-
(författare)
Cytotoxic Compounds of Plant Origin – Biological and Chemical Diversity
2005
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
The development of resistance by tumour cells to chemotherapeutic agents is a major problem in cancer treatments. One way to counter this is to find compounds with cytotoxic mechanisms other than those of drugs in clinical use today. The biological and chemical diversity encountered in Nature provide opportunities to discover completely new chemical classes of compounds. Some of these may represent previously unknown anticancer agents, and in some cases, novel, potentially relevant cytotoxic mechanisms. The selection of plants for the cytotoxic investigation in this project was designed to cover large parts of the angiosperm system, providing a broad representation of species. Extracts of the plants were subjected to a polypeptide fractionation protocol, followed by bioassay-guided isolation, yielding series of fractions with increasing purity and cytotoxicity. The cytotoxicity assay included tumour cells from patients and a cell-line panel including ten different cell lines representing several types of resistant and non-resistant tumours. This screening strategy allowed fractions and compounds acting with novel mechanisms to be detected at an early stage. The compounds isolated represent substantial chemical diversity and originate from diverse parts of the phylogenetic spectrum examined. They include the highly potent cytotoxic alkaloid, thiobinupharidine, the structure of which was determined by NMR techniques. Furthermore, two types of compound were shown to have previously unreported cytoxic activity: cyclotides (small macrocyclic polypeptides, in this case from violets) and polypeptides, possibly of thionine type, of loranthaceaeous mistletoes (collected in Panama). The well known cardiac glycosides from the foxglove, Digitalis, were identified as being responsible for the anti-tumour activity of this species.In conclusion, the results obtained in this project show that selection based on phylogenetic information, together with a robust and reliable method to detect cytotoxicity, can be a useful approach for exploring the plant kingdom for cytotoxic substances.
