The sesquiterpene trilactone bilobalide is one of the active constituents of the 50:1 Ginkgo biloba leaf extract widely used to enhance memory and learning. Bilobalide was found to antagonise the direct action of gamma-aminobutyric acid (GABA) on recombinant alpha(1)beta(2)gamma(2L) GABA(A) receptors. Bilobalide showed anticonvulsant properties through the activation of glutamic acid decarboxylase (GAD) enzyme, which is a key enzyme in biosynthesis of GABA. Bilobalide has been proposed to exert protective and trophic effects on neurons. Bilobalide may be useful in developing therapy for diseases involving age-associated neurodegeneration. Bilobalide is an active component of EGb, a standardised extract of Ginkgo biloba leaves. Bilobalide accounts for about 3% of the total extract.