Bilobalide

Bilobalide

Clinical data
Routes of administration	oral
Legal status
Legal status	legal
Identifiers
IUPAC name (5aR- (3aS*,5aα,8b,8aS*,9a,10aα))- 9-(1,1-dimethylethyl)- 10,10a-dihydro- 8,9-dihydroxy- 4H,5aH,9H-furo[2,3-b]furo[3',2':2,3]cyclopenta[1,2-c]furan- 2,4,7(3H,8H)-trione
CAS Number	33570-04-6
PubChem (CID)	73581
IUPHAR/BPS	2366
ChemSpider	21106418
ChEMBL	CHEMBL133266
Chemical and physical data
Formula	C15H18O8
Molar mass	326.299 g/mol
3D model (Jmol)	Interactive image
SMILES CC(C)(C)[C@@]1(C[C@H]2[C@@]3([C@]14[C@H](C(=O)O[C@H]4OC3=O)O)CC(=O)O2)O
InChI InChI=1S/C15H18O8/c1-12(2,3)14(20)4-6-13(5-7(16)21-6)10(19)23-11-15(13,14)8(17)9(18)22-11/h6,8,11,17,20H,4-5H2,1-3H3/t6-,8-,11-,13-,14+,15?/m0/s1 Key:MOLPUWBMSBJXER-ISSLQHLCSA-N
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Bilobalide is a biologically active terpenic trilactone present in Ginkgo biloba.^[1]

Chemistry

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 from farnesyl pyrophosphate is still unknown.

Biosynthesis

Bilobalide and ginkgolide both have very similar biosynthesis pathway. Bilobalide is formed by partially degraded from ginkgoglide. Bilibalide is derived from geranylgeranyl pyrophosphate (GGPP), which is formed by addition of farnesyl pyrophosphate (FPP) to isopentenyl pyrophosphate (IPP) unit, to form a C₁₅ sesquiterpene. Such formation went through the mevalonate pathway (MVA) and methylerythritol 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 enzyme abietadiene 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]

Pharmacology

Bilobalide is important for producing several of the effects of Gingko biloba extracts, and it has neuroprotective effects,^[3][4] as well as inducing the liver enzymes CYP3A1 and 1A2,^[5] which may be partially responsible for interactions between gingko and other herbal medicines or pharmaceutical drugs. Bilobalide has recently been found to be a negative allosteric modulator at the GABA_A and GABA_A-rho receptors.^[6] Of GABA_A, it may possibly be selective for the subunits predominantly implicated in cognitive and memory functioning such as α1.

See also

• Ginkgolide

References

1. van Beek TA, Montoro P (2009). "Chemical analysis and quality control of Ginkgo biloba leaves, extracts, and phytopharmaceuticals". Journal of Chromatography A. 1216 (11): 2002–32. doi:10.1016/j.chroma.2009.01.013. PMID 19195661.
2. Dewick, P. M. Medicinal Natural Products: Products:A Biosynthetic Approach. Third Edition ed.; Wiley&Sons: West Sussex, England, 2009; p 230-232.
3. Defeudis FV (2002). "Bilobalide and neuroprotection". Pharmacological Research. 46 (6): 565–8. doi:10.1016/S1043-6618(02)00233-5. PMID 12457632.
4. Kiewert C, Kumar V, Hildmann O, Hartmann J, Hillert M, Klein J (2008). "Role of glycine receptors and glycine release for the neuroprotective activity of bilobalide". Brain Research. 1201: 143–50. doi:10.1016/j.brainres.2008.01.052. PMID 18325484.
5. Deng Y, Bi HC, Zhao LZ, He F, Liu YQ, Yu JJ, Ou ZM, Ding L, Chen X, Huang ZY, Huang M, Zhou SF (2008). "Induction of cytochrome P450s by terpene trilactones and flavonoids of the Ginkgo biloba extract EGb 761 in rats". Xenobiotica. 38 (5): 465–81. doi:10.1080/00498250701883233. PMID 18421621.
6. http://sydney.edu.au/medicine/pharmacology/adrien-albert/images/pdfs/RefsPDFs/376.pdf