chemistry

Salazinic acid

Salazinic 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 Salazinic acid rather than just read about it. In short: Salazinic acid is a depsidone with a lactone ring. It is found in some lichens, and is especially prevalent in Parmotrema and Bulbothrix, where its presence or absence is often used to help classify species in those genera.

Key takeaways

Salazinic 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 Salazinic acid to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Salazinic acid from memory before moving on to harder problems.

Reference excerpt

Salazinic acid is a depsidone with a lactone ring. It is found in some lichens, and is especially prevalent in Parmotrema and Bulbothrix, where its presence or absence is often used to help classify species in those genera.

History In 1897, Friedrich Wilhelm Zopf named the chemical he originally isolated from the African species Stereocaulon salazinum as salazinic acid. Later studies showed that the compound he named was actually norstictic acid. In 1933, Yasuhiko Asahina and J. Asano studied salazinic acid they had isolated from Parmelia cetrata, and found a unique ring system with seven members containing two phenolic components. The fundamental structure was named depsidone, that is, a seven-membered ring with an oxygen bridge binding two aromatic rings. Japanese chemists demonstrated in the late 1960s that the isolated mycobiont of the lichen Ramalina crassa could produce salazinic acid when grown in laboratory culture. Subsequent studies tried to determine the influence of environmental factors on the production of salazinic acid in culture. For example, two studies in the late 1980s showed that only 4-O-demethylbarbatic acid (a precursor of salazinic acid) was produced by the isolated mycobiont of Ramalina siliquosa when grown in malt yeast extract medium supplemented with low amounts of sucrose. When extra sucrose was added to the growth medium, the production of salazinic acid was observed; the increased osmolality enhances the reaction from 4-O-demethylbarbatic acid to salazinic acid.

Properties Salazinic acid has a molecular formula of C18H12O10, and a molecular mass of 388.3 grams/mole. In its purified form, it exists as colourless needles with a melting point range between 260–268 °C (500–514 °F) that undergo a colour change to brown at about 240 °C (464 °F). Its solubility in water is about 27 milligrams per litre. The compound has been shown in in vitro studies to have antimicrobial properties, but it did not have any substantive antimycobacterial effects when tested against Mycobacterium aurum. Recent (2021) research indicates that salazinic acid is a potent modulator of Nrf2, NF-κB and STAT3 signaling pathways in colorectal cancer cells. The complete 1H and 13C NMR spectral assignments for salazinic acid were reported in 2000.

Occurrence

Salazinic acid is derived via the acetyl polymalonyl pathway, a metabolic pathway that uses acetyl-CoA and malonyl-CoA (derivatives of coenzyme A). The compound is common in the large lichen genus Parmotrema, and plays an important role in the chemotaxonomy and systematics of that genus. A 2020 revision included 66 salazinic acid-containing species. The presence or absence of the compound is also important in the classification of genus Bulbothrix. In nature, salazinic acid serves as an antioxidant as well as a photoprotectant, helping the lichen to survive in conditions of both abiotic and biotic stress. A study of three foliose lichen species showed higher quantities of salazinic acid correlating with increases in altitude. An earlier study demonstrated other possible effects of environmental conditions on salazinic acid content. It was shown that the salazinic acid content of Ramalina siliquosa is higher where the annual mean temperature is higher, and the content of the lichens growing on the dark-coloured rock or on the southern rock face is higher than that of the lichens growing on the light-coloured rock or on the northern rock face.

Related compounds The depsidones chalybaeizanic acid and quaesitic acid, isolated from the lichens Xanthoparmelia amphixanthoides and Hypotrachyna quaesita, respectively, are structurally similar to salazinic acid. In consalazinic acid, the aldehyde group of salazinic acid is replaced with a benzyl alcohol functional group. 8'-O-Methylsalazinic acid was isolated from Parmotrema dilatatum. Several new synthesised derivatives of salazinic acid were reported in 2021 using bromination, nucleophilic addition, Friedel-Crafts alkylation, and esterification.

Eponyms Several authors have explicitly named salazinic 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 taxonomic authority and year of publication:

Acanthothecis salazinica van den Boom & Sipman (2013) Bryoria salazinica Brodo & D.Hawksw. (1977) Graphina salazinica A.W.Archer (2001) Karoowia salazinica Hale (1989) Lepraria salazinica Tønsberg (2007) Myelochroa salazinica Sheng L.Wang, J.B.Chen & Elix (2001) Ocellularia salazinica Papong, Mangold & Lücking (2014) Pertusaria salazinica A.W.Archer & Elix (2017) Phaeographina salazinica A.W.Archer (2003) Psiloparmelia salazinica Elix & T.H.Nash (1992) Diorygma salazinicum Sutjar. & Kalb (2014) Oropogon salazinicus Essl. (1989)

References

Illustrations

Worked examples

Example 1 — a first encounter with Salazinic acid

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

In research: Salazinic 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 Salazinic 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: Salazinic acid is common in secondary-school and first-year university syllabi. It links to neighbouring topics Benzofurans, Dibenzodioxepines, Heterocyclic compounds with 4 rings, so understanding it makes those chapters shorter.
In everyday life: Look for Salazinic 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 Salazinic acid in 20 minutes

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

Frequently asked questions

What is Salazinic acid in simple terms?

Why does Salazinic 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 Salazinic 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 Salazinic acid.