chemistry

Protocetraric acid

Protocetraric acid 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 Protocetraric acid rather than just read about it. In short: Protocetraric acid is a chemical compound with the molecular formula C18H14O9. It is a secondary metabolite produced by a variety of lichens and is classified as a depsidone.

Key takeaways

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

Reference excerpt

Protocetraric acid is a chemical compound with the molecular formula C18H14O9. It is a secondary metabolite produced by a variety of lichens and is classified as a depsidone.

History In 1845 Knop and Schnedermann isolated crystalline cetraric acid from the lichen Cetraria islandica. O. Hesse proposed that cetraric acid does not exist in the lichen, but is rather the decomposition product of another acid that he called protocetraric acid, which is split up into fumaric and cetraric acids. In reviewing Hesse's work. O. Simon confirmed the statements of Knop and Schnedermann, finding cetraric acid in the plant in a free state. O. Simon did not find the protocetraric acid proposed by Hesse, but instead used that name for another acid he isolated. Protocetraric acid was first described in the 1930s. Rao and colleagues published the ultraviolet and infrared spectra of some lichen depsidones, including protocetraric acid, in 1967.

Properties The molecular formula of protocetraric acid is C18H14O9; it has a molecular mass of 374.29 grams per mole. In its purified crystalline form, it exists as short needles with a melting point range of 245–250 °C (473–482 °F). Its ultraviolet spectrum has three peaks of maximum absorption (λmax) at 210, 238, and 312 nm. Its infrared spectrum has several peaks: 680, 745, 785, 814, 840, 990, 1020, 1080, 1115, 1150, 1190, 1270, 1380, 1440, 1562, 1642, 1738, 3000, and 3500 cm−1. A number of ester derivatives of protocetraric acid, such as succinprotocetraric acid and fumarprotocetraric acid, have also been identified in lichens. Preliminary research has been conducted into the potential pharmacology of protocetraric acid and related compounds. Protocetraric acid has broad spectrum antimicrobial properties against some pathogenic microbes such as Salmonella typhi. It also has weak activity against SARS-CoV-2 3C-like protease (Ki of 3.95 μM), as does the related depsidone salazinic acid, and therefore it is being studied as a scaffold for the potential discovery of more potent drugs for the treatment of COVID-19.

Biological activities Laboratory experiments indicate that protocetraric acid has broad spectrum antimicrobial activity against some pathogenic microbes, including antibacterial activity against Salmonella typhi, and antifungal activity against Trichophyton rubrum. It also has moderate antimycobacterial activity on the growth of Mycobacterium tuberculosis.

Eponyms Some authors have explicitly named protocetraric acid in the specific epithets of their published lichen species, thereby acknowledging the presence of this compound as an important taxonomic characteristic. These eponyms are listed here, followed by their author citation and year of publication.

Usnea hossei var. protocetrarica G.N.Stevens (1999) Hypotrachyna protocetrarica Elix, T.H.Nash & Sipman (2009) Karoowia protocetrarica Hale (1989) Myriotrema protocetraricum (Hale) Hale (1980) Ocellularia protocetrarica Hale (1978) Opegrapha protocetrarica Seavey & J.Seavey (2014) Oropogon protocetraricus S.D.Leav. & Essl. (2013) Xanthoparmelia protocetrarica (Hale) G.Amo, A.Crespo, Elix & Lumbsch (2010) Several derivatives of protocetraric acid were designed and synthesised using Diels-Alder reaction, esterification, and Friedel-Crafts alkylation of protocetraric acid with different reagents under Lewis acid. The products were tested for their α-Glucosidase inhibitory using molecular docking analysis.

Related compounds The related chemical 9'-(O-methyl)protocetraric acid was isolated from the lichen Cladonia convoluta. Conhypoprotocetraric acid, identified from lichens Relicina cf. incongrua and Lecanora myriocarpoides, was synthesized and characterized in 1995.

Confumarprotocetraric acid Conhyopoprotocetraric acid Conprotocetraric acid Consuccinprotocetraric acid Fumarprotocetraric acid Hypoprotocetraric acid Malonprotocetraric acid 4-0-Methylhypoprotocetraric acid Succinprotocetraric acid

References

Cited literature Huneck, Siegfried (1996). Identification of Lichen Substances. Berlin, Heidelberg: Springer Berlin Heidelberg. ISBN 978-3-642-85245-9. OCLC 851387266.

Illustrations

Worked examples

Example 1 — a first encounter with Protocetraric acid

Start with the simplest possible case. Write down what Protocetraric acid 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 Protocetraric acid 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 Protocetraric acid 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 Protocetraric acid

In research: Protocetraric acid 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 Protocetraric acid 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: Protocetraric acid is common in secondary-school and first-year university syllabi. It links to neighbouring topics Alpha hydroxycarboxylic acids, Aromatic aldehydes, Dibenzodioxepines, so understanding it makes those chapters shorter.
In everyday life: Look for Protocetraric acid 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 Protocetraric acid in 20 minutes

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Close the page and write down what Protocetraric acid means in your own words.
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Frequently asked questions

What is Protocetraric acid in simple terms?

Protocetraric acid is a chemical compound with the molecular formula C18H14O9. It is a secondary metabolite produced by a variety of lichens and is classified as a depsidone.

Why does Protocetraric acid 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 Protocetraric acid?

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 Protocetraric acid.