Ginkgo Biloba supplies a standardized extract of Ginkgo Biloba, along with antioxidant enzymes SOD and catalase. According to a review by Birks and Evans, Ginkgo's "mechanisms of action are thought to reflect the action of several components of the extract and include increasing blood supply by dilating blood vessels, reducing blood viscosity, modification of neurotransmitter systems, and reducing the density of oxygen free radicals." {Birks J, Grimley EJ. Ginkgo biloba for cognitive impairment and dementia. Cochrane Database of Systematic Reviews 2009, Issue 1. Art. No.:CD003120.}