title: Flavonoids in Helichrysum pamphylicum inhibit mammalian type I DNA topoisomerase.
abstract: DNA topoisomerases are important targets for cancer chemotherapy. We investigated the effects of a methanolic extract of Helichrysum pamphylicum on mammalian DNA topoisomerase I via in vitro plasmid supercoil relaxation assays. The extracts manifested a considerable inhibition of the enzyme's activity in a dose-dependent manner. We also performed a HPLC analysis to identify the flavonoid content of the H. pamphylicum extract and tested the identified flavonoids; luteolin, luteolin-4-glucoside, naringenin, helichrysinA and isoquercitrin, on DNA topoisomerase I activity. The measurement of the total antioxidant capacity of the flavonoid standards suggested that the topoisomerase inhibition might be correlated with the antioxidant capacity of the plant.
authors.affiliation: Department of Pharmaceutical Biotechnology, Faculty of Pharmacy, Ege University, 35100 Izmir, Turkey. zeki.topcu@ege.edu.tr
authors.forename: Zeki
authors.initials: Z
authors.lastname: Topcu
authors.forename: Bintug
authors.initials: B
authors.lastname: Ozturk
authors.forename: Ozlem
authors.initials: O
authors.lastname: Kucukoglu
authors.forename: Emrah
authors.initials: E
authors.lastname: Kilinc
mesh_terms: D000818:Animals; D002853:Chromatography, Liquid; D004278:DNA, Superhelical / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D005419:Flavonoids / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D036562:Helichrysum / Q000737:chemistry*; D007700:Kinetics; D008322:Mammals; D010936:Plant Extracts / Q000494:pharmacology; D010957:Plasmids / Q000187:drug effects; D059004:Topoisomerase I Inhibitors
chemical_list: D004278:DNA, Superhelical; D004791:Enzyme Inhibitors; D005419:Flavonoids; D010936:Plant Extracts; D059004:Topoisomerase I Inhibitors