Ginkgo contains many different substances.Most of them fall into two categories Flavnoids and Terpenoids or Terpene lactoids.
Flavnoids are naturally occurring substances that function as anti-oxidants (scavenge free radicals-damaging compounds in the body that alter cell membranes, tamper with DNA, and even cause cell death) also found in fruits and vegetables.They enhance the immune system in the body and interfere with tumor formation.The type of flavonoid in Ginkgo is called Ginkgolide. Ginkgolides are very unique compounds exclusive to Ginkgo and are broken down into separate ginkgolides A, B, C, J, and M.Each Ginkgolide has a different degree of potency.Ginkgolide B is considered the most active.Other flavnoids present are quercitin (which is one of the most studied flavnoids and is a stronger antioxidant than vitamin E), and kaempferol.
Terpene lactones are the active constituents that give ginkgo a bitter strong flavor and helps increase blood circulation.
Other components present are Amino Acid-6hydrozykynurenic acid, Dimeric flavones (bilobetin, ginkgetin, isoginkgetin, scieadopitysin), Proanthocyanidins, ginkgolic acid, ascorbic acid, carotenoids, and Bilobalide.
The nuts contain essential oil, fatty acid, tannin, and resin.
 Tredici, Peter Del, Ginkgo biloba (ebooks: Hardwood Publishers imprint, part of the Gordon & Breach Publishing Group, c2000) p. 274