title: Mechanistic evaluation of Ginkgo biloba leaf extract-induced genotoxicity in L5178Y cells.
abstract: Ginkgo biloba has been used for many thousand years as a traditional herbal remedy and its extract has been consumed for many decades as a dietary supplement. Ginkgo biloba leaf extract is a complex mixture with many constituents, including flavonol glycosides and terpene lactones. The National Toxicology Program 2-year cancer bioassay found that G. biloba leaf extract targets the liver, thyroid gland, and nose of rodents; however, the mechanism of G. biloba leaf extract-associated carcinogenicity remains unclear. In the current study, the in vitro genotoxicity of G. biloba leaf extract and its eight constituents was evaluated using the mouse lymphoma assay (MLA) and Comet assay. The underlying mechanisms of G. biloba leaf extract-associated genotoxicity were explored. Ginkgo biloba leaf extract, quercetin, and kaempferol resulted in a dose-dependent increase in the mutant frequency and DNA double-strand breaks (DSBs). Western blot analysis confirmed that G. biloba leaf extract, quercetin, and kaempferol activated the DNA damage signaling pathway with increased expression of γ-H2AX and phosphorylated Chk2 and Chk1. In addition, G. biloba leaf extract produced reactive oxygen species and decreased glutathione levels in L5178Y cells. Loss of heterozygosity analysis of mutants indicated that G. biloba leaf extract, quercetin, and kaempferol treatments resulted in extensive chromosomal damage. These results indicate that G. biloba leaf extract and its two constituents, quercetin and kaempferol, are mutagenic to the mouse L5178Y cells and induce DSBs. Quercetin and kaempferol likely are major contributors to G. biloba leaf extract-induced genotoxicity.
authors.affiliation: Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, Arkansas 72079.
authors.forename: Haixia
authors.initials: H
authors.lastname: Lin
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Guo
authors.forename: Suhui
authors.initials: S
authors.lastname: Zhang
authors.forename: Stacey L
authors.initials: SL
authors.lastname: Dial
authors.forename: Lei
authors.initials: L
authors.lastname: Guo
authors.forename: Mugimane G
authors.initials: MG
authors.lastname: Manjanatha
authors.forename: Martha M
authors.initials: MM
authors.lastname: Moore
authors.forename: Nan
authors.initials: N
authors.lastname: Mei
mesh_terms: D000818:Animals; D018929:Cell Culture Techniques; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D020552:Comet Assay; D004249:DNA Damage; D004305:Dose-Response Relationship, Drug; D020441:Ginkgo biloba / Q000737:chemistry*; D005978:Glutathione / Q000378:metabolism; D044949:Kaempferols / Q000633:toxicity; D051379:Mice; D009153:Mutagens / Q000633:toxicity*; D010936:Plant Extracts / Q000633:toxicity*; D018515:Plant Leaves / Q000737:chemistry; D011794:Quercetin / Q000633:toxicity; D017382:Reactive Oxygen Species / Q000378:metabolism; D000096983:Ginkgo Extract
chemical_list: D005978:Glutathione; D044949:Kaempferols; D009153:Mutagens; D010936:Plant Extracts; D011794:Quercetin; D017382:Reactive Oxygen Species; C583942:Ginkgo biloba extract 50; D000096983:Ginkgo Extract; C006552:kaempferol
keywords: DNA damage; Ginkgo biloba leaf extract; genotoxicity; kaempferol; oxidative stress; quercetin; quercetin 3-β-d-glucoside