title: Use of COMPARE analysis to discover new natural product drugs: isolation of camptothecin and 9-methoxycamptothecin from a new source.
abstract: Analysis of cytotoxicity data of extracts from the National Cancer Institute's Active Repository by the COMPARE protocol was carried out using camptothecin as a reference point. Extracts identified by this process were further characterized by a selective yeast bioassay for inhibitors of topoisomerase I and by a biochemical assay for compounds that stabilize the topoisomerase I-DNA covalent binary complex. Five of the extracts were positive in the yeast bioassay, and eight extracts showed activity on the assay that monitors stabilization of the topoisomerase I-DNA complex. Four of the latter extracts were inactive in the yeast bioassay, and thus would not have been identified as hits without the COMPARE preselection process. One of the extracts, from Pyrenacantha klaineana, was selected for detailed investigation, and fractionation of this extract yielded camptothecin and 9-methoxycamptothecin as the bioactive constituents.
authors.affiliation: Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0212, USA.
authors.forename: B N
authors.initials: BN
authors.lastname: Zhou
authors.forename: J M
authors.initials: JM
authors.lastname: Hoch
authors.forename: R K
authors.initials: RK
authors.lastname: Johnson
authors.forename: M R
authors.initials: MR
authors.lastname: Mattern
authors.forename: W K
authors.initials: WK
authors.lastname: Eng
authors.forename: J
authors.initials: J
authors.lastname: Ma
authors.forename: S M
authors.initials: SM
authors.lastname: Hecht
authors.forename: D J
authors.initials: DJ
authors.lastname: Newman
authors.forename: D G
authors.initials: DG
authors.lastname: Kingston
mesh_terms: D000465:Algorithms; D000972:Antineoplastic Agents, Phytogenic / Q000302:isolation & purification* / Q000494:pharmacology; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000302:isolation & purification* / Q000494:pharmacology; D004354:Drug Screening Assays, Antitumor / Q000379:methods*; D004791:Enzyme Inhibitors / Q000302:isolation & purification / Q000494:pharmacology; D013057:Spectrum Analysis; D059004:Topoisomerase I Inhibitors
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D004791:Enzyme Inhibitors; D059004:Topoisomerase I Inhibitors; C025724:9-methoxycamptothecin; D002166:Camptothecin