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| Routes of administration | By mouth |
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| ECHA InfoCard | 100.125.716 |
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| Formula | C15H18O8 |
| Molar mass | 326.301 g·mol−1 |
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Bilobalide is a biologically activeterpenic trilactone present inGinkgo biloba.[1]
Bilobalide is a main constituent of the terpenoids found in Ginkgo leaves. It also exists in minor amounts in the roots. It is a sesquiterpenoid, i.e. it has a 15-carbon skeleton. Its exact synthesis pathway fromfarnesyl pyrophosphate is still unknown.
Bilobalide and ginkgolide have similar biosynthetic pathways. Bilobalide is formed by partially degraded ginkgolide. Bilobalide is derived fromgeranylgeranyl pyrophosphate (GGPP), which is formed by addition offarnesyl pyrophosphate (FPP) to anisopentenyl pyrophosphate (IPP) unit to form a C15sesquiterpene. Such formation went through themevalonate pathway (MVA) andmethylerythritol phosphate MEP pathway. In order to generate bilobalide, C20 ginkgolide 13 must form first. To transform from GGPP to abietenyl cation 5, a single bifunctional enzymeabietadiene synthase E1 is required. However, due to the complexity of ginkgolide structures for rearrangement, ring cleavage, and formation of lactone rings, diterpene 8 is used to explain instead. Levopimaradiene 6 and abietatriene 7 are precursors for ginkgolide and bilobalide formation. The unusual tert-butyl substituent is formed from A ring cleavage in 9. Bilobalide 13 then formed in loss of carbons through degradation from ginkgolide 12, and lactones are formed from residual carboxyl and alcohol functions. The end product of bilobalide contains sesquiterpenes and three lactones units.[2]
Bilobalide is important for producing several of the effects ofGinkgo biloba extracts, and it has neuroprotective effects,[3][4] as well as inducing the liver enzymes CYP3A1 andCYP1A2,[5] which may be partially responsible for interactions between ginkgo and other herbal medicines or pharmaceutical drugs. Bilobalide has recently been found to be anegative allosteric modulator at theGABAA andGABAA-rho receptors.[6] Of GABAA, it may possibly be selective for the subunits predominantly implicated in cognitive and memory functioning such asα1[citation needed].
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