Sesquiterpene isolated from the leaves of Ginko biloba L., Ginkgoaceae; closely related to the ginkgolides, q.v. Component of the Ginkgo biloba extract, EGb 761, q.v. Isoln: K. Weinges, W. B"ahr, Ann. 724, 214 (1969). NMR and MS analysis: eidem, ibid. 759, 158 (1972). Structure determn: K. Nakanishi et al., J. Am. Chem. Soc. 93, 3544 (1971). Total synthesis of (±)-form: E. J. Corey, W. Su, ibid. 109, 7534 (1987). Enantioselective synthesis of (-)-form: eidem, Tetrahedron Lett. 29, 3423 (1988). Separation from Ginkgo biloba extracts: S. Jaracz et al., Phytochemistry 65, 2897 (2004). Neuroprotective effects in animal models of brain ischemia: K. Chandrasekaran et al., Brain Res. 922, 282 (2001). GABAA antagonist activity: S. H. Huang et al., Eur. J. Pharmacol. 464, 1 (2003). Review of neuroprotective properties: F. V. Defeudis, Pharmacol. Res. 46, 565-568 (2002); of physical properties: T. A. van Beek, Bioorg. Med. Chem. 13, 5001-5012 (2005).