science

Homosalate

Homosalate is a science 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 Homosalate rather than just read about it. In short: Homosalate is an organic compound used in some sunscreens. It is made by the Fischer–Speier esterification of salicylic acid and 3,3,5-trimethylcyclohexanol, the latter being a hydrogenated derivative of isophorone.

Key takeaways

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

Reference excerpt

Homosalate is an organic compound used in some sunscreens. It is made by the Fischer–Speier esterification of salicylic acid and 3,3,5-trimethylcyclohexanol, the latter being a hydrogenated derivative of isophorone. Contained in 45% of U.S. sunscreens, it is used as a chemical UV filter. The salicylic acid portion of the molecule absorbs ultraviolet rays with a wavelength from 295 nm to 315 nm, protecting the skin from sun damage. The hydrophobic trimethyl cyclohexyl group provides greasiness that prevents it from dissolving in water.

Safety Homosalate was identified in a court case brought by German chemical company Symrise who claimed that the ingredient used in sunscreen did not require animal testing. Symrise lost the appeal against a European Chemicals Agency (ECHA) decision that requires the German manufacturer to test sunscreen ingredients on animals. The Court of Justice of the European Union (CJEU) decision applies to two formerly approved ingredients used exclusively in sunscreens — UV filter homosalate and 2-ethylhexyl salicylate. Similar to other UV filter compounds, more homosalate is absorbed into the uppermost stratum corneum (ie, the stratum disjunctum) of the face (25% of applied dose) versus back of volunteers. This amounted to approximately two to three times the amount of sunscreen that was present in the superficial stratum corneum layers of the face compared with the back. There was no homosalate detected in the urine samples or blood plasma samples of the volunteers in this study. Homosalate has been identified as an antiandrogen (testosterone blocker) in vitro, as well as having estrogenic activity toward estrogen receptors α, and general in vitro estrogenic activity. Homosalate has been shown to be an antagonist toward androgen and estrogen receptors in vitro. Some work has shown that organic UV filters in general can present concerns. There is no in vivo evidence of toxicity, endocrine dysfunction or adverse effects; and none of these adverse events have ever been reported to occur in humans. An in vivo study involving repeated subcutaneous injections of homosalate at dose levels up to 1000mg/kg of body weight to juvenile female Wistar rats over three consecutive days revealed no estrogenic potential in the uterotrophic assay. Another study on immature Long–Evans rats receiving up to 892 mg/kg of body weight of homosalate in their daily diet found no estrogenic effects in vivo. Research on zebra fish also found no estrogenic effects after being continuously exposed to homosalate for 96 hours straight. The SCCS has declared there is no sufficient evidence that identifies pure homosalate as an endocrine disruptor in humans and further declared that in vivo research has confirmed that homosalate has no genotoxic, phototoxic or photosensitive effects when applied topically.

References

Illustrations

Worked examples

Example 1 — a first encounter with Homosalate

Start with the simplest possible case. Write down what Homosalate claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Homosalate 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 Homosalate 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 Homosalate

In research: Homosalate appears in science 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 Homosalate 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: Homosalate is common in secondary-school and first-year university syllabi. It links to neighbouring topics 3,3,5-Trimethylcyclohexyl esters, 3-Hydroxypropenals, Salicylate esters, so understanding it makes those chapters shorter.
In everyday life: Look for Homosalate 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 Homosalate in 20 minutes

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

Frequently asked questions

What is Homosalate in simple terms?

Why does Homosalate matter?

Because it connects several science 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 Homosalate?

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 Homosalate.