chemistry

Procyanidin

Procyanidin is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Procyanidin rather than just read about it. In short: Procyanidins are members of the proanthocyanidin (or condensed tannins) class of flavonoids. They are oligomeric compounds, formed from catechin and epicatechin molecules.

Key takeaways

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

Reference excerpt

Procyanidins are members of the proanthocyanidin (or condensed tannins) class of flavonoids. They are oligomeric compounds, formed from catechin and epicatechin molecules. They yield cyanidin when depolymerized under oxidative conditions. See the box below entitled "Types of procyanidins" for links to articles on the various types.

Distribution in plants Procyanidins, including the lesser bioactive / bioavailable polymers (4 or more catechines), represent a group of condensed flavan-3-ols that can be found in many plants, most notably apples, maritime pine bark, cinnamon, aronia fruit, cocoa beans, grape seed, grape skin, and red wines of Vitis vinifera (the common grape). However, bilberry, cranberry, black currant, green tea, black tea, and other plants also contain these flavonoids. Procyanidins can also be isolated from Quercus petraea and Q. robur heartwood (wine barrel oaks). Açaí oil, obtained from the fruit of the açaí palm (Euterpe oleracea), is rich in numerous procyanidin oligomers. Apples contain on average per serving about eight times the amount of procyanidin found in wine, with some of the highest amounts found in the Red Delicious and Granny Smith varieties. The seed testas of field beans (Vicia faba) contain procyanidins that affect the digestibility in piglets and could have an inhibitory activity on enzymes. Cistus salviifolius also contains oligomeric procyanidins.

Analysis Condensed tannins can be characterised by a number of techniques including depolymerisation, asymmetric flow field flow fractionation or small-angle X-ray scattering. DMACA is a dye used for localization of procyanidin compounds in plant histology. The use of the reagent results in blue staining. It can also be used to titrate procyanidins. Total phenols (or antioxidant effect) can be measured using the Folin-Ciocalteu reaction. Results are typically expressed as gallic acid equivalents (GAE). Procyanidins from field beans (Vicia faba) or barley have been estimated using the vanillin-HCl method, resulting in a red color of the test in the presence of catechin or proanthocyanidins. Procyanidins can be titrated using the Procyanidolic Index (also called the Bates-Smith Assay). It is a testing method that measures the change in color when the product is mixed with certain chemicals. The greater the color changes, the higher the PCOs content is. However, the Procyanidolic Index is a relative value that can measure well over 100. Unfortunately, a Procyanidolic Index of 95 was erroneously taken to mean 95% PCO by some and began appearing on the labels of finished products. All current methods of analysis suggest that the actual PCO content of these products is much lower than 95%. An improved colorimetric test, called the Porter Assay or butanol-HCl-iron method, is the most common PCO assay currently in use. The unit of measurement of the Porter Assay is the PVU (Porter Value Unit). The Porter Assay is a chemical test to help determine the potency of procyanidin containing compounds, such as grape seed extract. It is an acid hydrolysis, which splits larger chain units (dimers and trimers) into single unit monomers and oxidizes them. This leads to a colour change, which can be measured using a spectrophotometer. The greater the absorbance at a certain wavelength of light, the greater the potency. Ranges for grape seed extract are from 25 PVU for low grade material to over 300 for premium grape seed extracts. Gel permeation chromatography (GPC) analysis allows to separate monomers from larger PCO molecules. Monomers of procyanidins can be characterized by HPLC analysis. Condensed tannins can undergo acid-catalyzed cleavage in the presence of a nucleophile like phloroglucinol (reaction called phloroglucinolysis), thioglycolic acid (thioglycolysis), benzyl mercaptan or cysteamine (processes called thiolysis) leading to the formation of oligomers that can be further analyzed. Phloroglucinolysis can be used for instance for procyanidins characterisation in wine or in the grape seed and skin tissues. Thioglycolysis can be used to study procyanidins or the oxidation of condensed tannins. It is also used for lignin quantitation. Reaction on condensed tannins from Douglas fir bark produces epicatechin and catechin thioglycolates. Condensed tannins from Lithocarpus glaber leaves have been analysed through acid-catalyzed degradation in the presence of cysteamine.

Research Procyanidin content in dietary supplements has not been well documented. Pycnogenol is a dietary supplement derived from extracts from maritime pine bark that contains 70% procyanidins, and is marketed with claims it can treat many conditions. The medical evidence is insufficient to support its use for the treatment of seven different chronic disorders.

See also A type proanthocyanidin B type proanthocyanidin Procyanidin C1 Procyanidin C2 Tannin Polyphenol Phenolic compounds in wine

References

External links

"Pycnogenol: MedlinePlus Supplements"

Illustrations

Worked examples

Example 1 — a first encounter with Procyanidin

Start with the simplest possible case. Write down what Procyanidin 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 Procyanidin 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 Procyanidin 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 Procyanidin

In research: Procyanidin 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 Procyanidin 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: Procyanidin is common in secondary-school and first-year university syllabi. It links to neighbouring topics Flavonoid antioxidants, Food chemistry, Procyanidins, so understanding it makes those chapters shorter.
In everyday life: Look for Procyanidin 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.

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How to study Procyanidin in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Procyanidin 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 Procyanidin out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Procyanidin in simple terms?

Procyanidins are members of the proanthocyanidin (or condensed tannins) class of flavonoids. They are oligomeric compounds, formed from catechin and epicatechin molecules.

Why does Procyanidin 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 Procyanidin?

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 Procyanidin.