title: Flavonoid constituents of Chorizanthe diffusa with potential cancer chemopreventive activity.
abstract: An ethyl acetate-soluble extract of Chorizanthe diffusa was found to exhibit significant antioxidant activity, as judged by scavenging stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals and inhibition of 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced free radical formation with cultured HL-60 cells. Bioassay-directed fractionation of this extract using the DPPH antioxidant assay as a monitor led to the isolation of five structurally related flavonoids (1-5), including the novel compound 5,8,3',4',5'-pentahydroxy-3, 7-dimethoxyflavone (1). Isolates 1-5 demonstrated varying degrees of antioxidant or antimutagenic activity. Two of the compounds, 5,7,3', 4'-tetrahydroxy-3-methoxyflavone (2) and quercetin (4), were subsequently found to inhibit carcinogen-induced preneoplastic lesions in a mouse mammary organ culture model. Inhibitory activity of this type is known to correlate with cancer chemopreventive effects in full-term models of tumorigenesis.
authors.affiliation: Program for Collaborative Research in the Pharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA.
authors.forename: H S
authors.initials: HS
authors.lastname: Chung
authors.forename: L C
authors.initials: LC
authors.lastname: Chang
authors.forename: S K
authors.initials: SK
authors.lastname: Lee
authors.forename: L A
authors.initials: LA
authors.lastname: Shamon
authors.forename: R B
authors.initials: RB
authors.lastname: van Breemen
authors.forename: R G
authors.initials: RG
authors.lastname: Mehta
authors.forename: N R
authors.initials: NR
authors.lastname: Farnsworth
authors.forename: J M
authors.initials: JM
authors.lastname: Pezzuto
authors.forename: A D
authors.initials: AD
authors.lastname: Kinghorn
mesh_terms: D000818:Animals; D016588:Anticarcinogenic Agents / Q000032:analysis* / Q000494:pharmacology*; D005419:Flavonoids / Q000032:analysis* / Q000494:pharmacology*; D018922:HL-60 Cells; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D051379:Mice; D008807:Mice, Inbred BALB C; D010944:Plants / Q000737:chemistry*
chemical_list: D016588:Anticarcinogenic Agents; D005419:Flavonoids