Ginkgolide

Key takeaways

Ginkgolide belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Ginkgolide to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Ginkgolide from memory before moving on to harder problems.

Reference excerpt

Ginkgolides are biologically active terpenic lactones present in Ginkgo biloba. They are diterpenoids with 20-carbon skeletons, which are biosynthesized from geranylgeranyl pyrophosphate.

Examples

Ginkgolide A Ginkgolide A has a chemical formula of C20H24O9, its CAS No. is 15291-75-5. Aside from the G. Biloba tree, this ginkgolide has also been reported to be present in Machilus wangchiana. It is also biologically active. A study has concluded that Ginkgolide A can induce the CYP1A2 enzyme, but not as much as other chemicals present in Ginkgo. This means that Ginkgolide A can increase the action of CYP1A2. Ginkgolide A also acts as an antagonist of glycine receptors and α1β2γ2L GABAA receptors. Additionally, it acts as a powerful PAF antagonist.

Ginkgolide B Ginkgolide B, specifically, is a diterpenoid trilactone with six five-membered rings. It contains a spiro[4,4]-nonane carbocyclic ring, a tetrahydrofuran ring, and a very specific tert-butyl group at one of the rings (Figure 1). The class of ginkgolides was first isolated from the tree Ginkgo biloba in 1932. Structural elucidation was accomplished in 1967 by Maruyama et al.

Ginkgolide C Ginkgolide C is a ginkgolide with the chemical formula of C20H24O11 and the CAS number 15291-76-6. It is an inhibitor of PAFR with an IC50 value of 7.5μM. This ginkgolide also appears to possess anti-inflammatory properties and activity against oxidative stress. A total synthesis of Ginkgolide C has also been reported.

Background It is extracted from the root bark and leaves of the Ginkgo biloba (ginkyo meaning "silver apricot") tree found native in China. It is marketed to other countries that include Korea, France, the United States, etc. for the drug and clinical properties of the extracts. Present in the tree is less than 0.1 to 0.25% of ginkgolide B, the most abundant being ginkgolide A.

Potential applications This class of molecules has been studied for its potential to act as a platelet-activating factor receptor antagonist. Ginkgolide B has been investigated for its potential to reducing migraine frequency. Ginkgolide B is also used in treatment for cerebrovascular disease. Research has also proven that ginkgolide B can also treat migraines in young ages. The literature indicates that ginkgolide B functions as a selective antagonist of glycine receptors based on noncompetitive inhibition for the neurological system that this compound performs.

Spectroscopic studies for the elucidation of the individual structures for the ginkgolides Ginkolides A - C were isolated from a large scale methanolic extraction followed by liquid-liquid partitions, column chromatography and repeated crystallizations. The molecular formulas were determined by high resolution mass spectrometry, and the overall structures by IR and NMR spectroscopic analysis and extensive derivitization techniques.

Biosynthesis of ginkgolide B

While researchers have published chemical pathways to make this molecule, most of the designed syntheses were too complex and produced little of the actual material to run full analyses. Therefore, studying the biosynthesis of the molecule is preferable. Most of the natural product terpenoids start with isopentenyl diphosphate synthesized by the MEP pathway. This pathway also generates dimethylallyl diphosphate, from pyruvate and D-glyercaldehyde 3-phosphate (GAP). When coupled together, they form one molecule of geranylgeranyl diphosphate with geranylgeranyl diphosphate synthase. A molecule of GGPP generates (1) (+)-copalyl in the presence of levopimaradiene synthase. (a) Then (1) loses its OPP group catalyzed by this same synthase, performing an intramolecular allylic cyclization with the two alkenes, to form (2) the sandaracopimarenyl cation. (b) This cation then undergoes an internal cyclization to stabilize the carbocation in the ring by proton transfer to form (3) intermediate. (c) By doing this, the molecule sets itself up for a methyl migration to stabilize that secondary cation and generate that tertiary carbocation at (4). (d) This induces a loss of proton to get (5) levopimaradiene. (e) With oxidation, a loss of a proton to form an aromatic ring generates (6) abietatriene. (g) This newly formed abietatriene undergoes a 1,2-alkyl shift to break the 6-membered ring into (7) with a five-membered ring (more favorable). (h) Another 1,2-alkyl shift takes place at the same time a ring cleavage takes place to generate (8). (i) Oxidation at all the positions with alkenes generates (9) intermediate which then undergoes ring closures featuring one hemiacetal and all three lactones to get ginkgolide B at (10).

Illustrations

Ginkgolide: Chemical structure of ginkgolides — Chemical structure of ginkgolides

Worked examples

Example 1 — a first encounter with Ginkgolide

Start with the simplest possible case. Write down what Ginkgolide claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Ginkgolide before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Ginkgolide ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Ginkgolide

In research: Ginkgolide appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Ginkgolide in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Ginkgolide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cyclopentanes, Diterpenes, Gamma-lactones, so understanding it makes those chapters shorter.
In everyday life: Look for Ginkgolide outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Ginkgolide in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Ginkgolide means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Ginkgolide out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Ginkgolide in simple terms?

Ginkgolides are biologically active terpenic lactones present in Ginkgo biloba. They are diterpenoids with 20-carbon skeletons, which are biosynthesized from geranylgeranyl pyrophosphate.

Why does Ginkgolide matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Ginkgolide?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Ginkgolide.