New Coumarin Compounds Show Powerful Multitarget Potential Against Skin Aging

Scientists have designed a family of synthetic molecules that simultaneously block several of the key enzymes driving skin aging and hyperpigmentation, and one of them outperforms the gold-standard skin-lightening agent by roughly twenty-fold. The study, published in the open-access journal Results in Chemistry, describes the design, synthesis, and biological evaluation of eighteen coumarin-based compounds, and identifies a single lead molecule that combines tyrosinase inhibition, antioxidant activity, sun protection, and safety in human skin cells. The work, led by Sonia Floris, Benedetta Era, Francesca Pintus, Antonella Fais, Manuel Novás, and Maria J. Matos, offers a striking example of how rational, structure-guided chemistry can compress an entire anti-aging strategy into one small molecule.

The biological logic behind the research begins with tyrosinase, a copper-containing oxidase that catalyzes the first steps of melanin biosynthesis. When tyrosinase runs unchecked, melanin is overproduced, producing the dark patches characteristic of melasma, age spots, and post-inflammatory hyperpigmentation, conditions whose prevalence is growing as climate change intensifies ultraviolet exposure worldwide. Existing inhibitors such as kojic acid, arbutin, and hydroquinone are widely used but suffer from low stability, poor selectivity, and adverse effects with prolonged use, leaving dermatologists and cosmetic chemists searching for better scaffolds. Excessive tyrosinase activity has also been linked to oxidative stress and cellular damage, which means that an ideal inhibitor would ideally mop up reactive oxygen species at the same time.

But tyrosinase is only one actor in the aging drama. Three additional enzymes—elastase, collagenase, and hyaluronidase—systematically dismantle the extracellular matrix that keeps skin firm, elastic, and hydrated. Elastase degrades elastin, collagenase breaks down collagen, and hyaluronidase chops up hyaluronic acid, the molecule responsible for the skin’s moisture retention and plumpness. Their activation, triggered largely by reactive oxygen species, produces the wrinkles, dryness, and loss of firmness we recognize as skin aging. Because these processes run in parallel, the research team argued that a truly effective anti-aging compound should hit multiple targets at once rather than attacking a single pathway, and they turned to the coumarin scaffold as the foundation for such a multitarget agent.

Coumarins, an aromatic class of plant-derived compounds with a long history in dermatology, are structurally versatile: adding different substituents changes the electronic properties of the core and, with them, both antioxidant capacity and the ability to grip enzyme active sites. Building on years of prior work in which the group screened its in-house chemical library and identified 3-arylcoumarins with micromolar tyrosinase activity, the researchers used structure–activity relationships and molecular docking to design a new series. They strategically installed hydroxyl groups on the coumarin nucleus—because hydrogen-bond donors and acceptors strengthen binding to the tyrosinase catalytic site—and nitro groups on the 3-phenyl ring, exploiting the nitro group’s strong electron-withdrawing character to tune the molecule’s electronics and orientation within the enzyme pocket.

The synthesis relied on the Perkin-Oglialoro reaction, a two-step condensation the group has refined over several years. In the first step, a hydroxy-substituted phenylacetic acid and a hydroxylated salicylaldehyde are refluxed in acetic anhydride with potassium acetate, closing the coumarin ring while simultaneously acetylating the free hydroxyl groups. Ring closure is confirmed by the characteristic H-4 proton in the proton NMR spectrum. The second step hydrolyzes these acetyl groups in aqueous hydrochloric acid and methanol, releasing the free hydroxyl derivatives, whose low-field hydroxyl protons verify the final products. All eighteen compounds were fully characterized by proton and carbon NMR and mass spectrometry, providing the chemical foundation for the biological campaign that followed.

The biological results were dramatic. Of the eighteen compounds tested, six inhibited tyrosinase, and three did so far more potently than kojic acid, the standard inhibitor with an IC50 of 17.9 micromolar. The standout was compound 12, 6,7-dihydroxy-3-(4-nitrophenyl)coumarin, which inhibited the enzyme at an IC50 of just 0.9 micromolar—roughly twenty times more potent than kojic acid. Compounds 17 and 18, both 5,7-dihydroxy-3-(nitrophenyl)coumarins, followed at 2.6 and 5.7 micromolar, about seven-fold and three-fold better than the standard. The structure–activity relationship is telling: the 6,7-dihydroxy catechol arrangement paired with a para-nitrophenyl group proved optimal, and comparing compounds 17 and 18 showed that even the position of a single nitro group—meta versus para—shifts the biological response, likely by altering electron distribution and the orientation of the aryl ring in the binding site.

The three lead compounds were then tested against the extracellular-matrix-degrading enzymes, and here the multitarget promise truly materialized. All three inhibited elastase, with compound 18 matching the reference inhibitor oleanolic acid at 20.5 micromolar. Against collagenase, all three derivatives recorded IC50 values statistically lower than the epigallocatechin gallate reference, with compound 18 reaching 124.6 micromolar. The most striking results came from hyaluronidase: compounds 12, 17, and 18 were 7.6-, 4.4-, and 4.4-fold more potent than oleanolic acid, respectively, with compound 12 active at 27.8 micromolar. Together, these data show that a single 3-arylcoumarin framework can suppress the entire enzymatic cascade that degrades collagen, elastin, and hyaluronic acid.

Antioxidant and photoprotective assays rounded out the profile. In ABTS and DPPH radical-scavenging assays, four compounds were active in both tests, and in the DPPH assay their EC50 values were significantly lower than that of Trolox, the vitamin E derivative used as the antioxidant benchmark. Compound 12 again distinguished itself, combining strong radical scavenging with the highest sun protection factor of the series, measured by UV spectrophotometry across the 290 to 320 nanometer range using the Mansur equation. Crucially, when the compound was applied to HaCaT human keratinocytes—a well-established in vitro model of the human epidermis—at concentrations from 1 to 25 micromolar for 24 hours, an MTT viability assay showed no cytotoxicity, an essential early safety signal for any topical candidate.

Molecular docking explained why compound 12 works so well. Using the crystal structure of tyrosinase from Agaricus bisporus, the team validated their protocol by re-docking the co-crystallized inhibitor tropolone, achieving a root-mean-square deviation of 1.373 angstroms, well within the reliability threshold. The predicted pose of compound 12 places its 7-hydroxyl oxygen within coordinating distance of one of the two catalytic copper ions, forming a coordination bond that would block natural substrates from entering the catalytic site and halt the monophenolase and diphenolase reactions that ultimately polymerize into melanin. The predicted binding energy of −7.9 kilocalories per mole for compound 12, and −8.7 and −8.6 for compounds 17 and 18, compares favorably with tropolone’s −6.0, and ligand efficiencies above 0.3 kilocalories per mole per heavy atom mark all three as fragment-like hits ripe for optimization. Docking also revealed that a meta-nitro group, as in compound 17, enables a hydrogen bond with the conserved residue ASN260 near the binuclear copper center, an interaction absent in the para-nitro analogues.

The authors are careful to frame their structure–activity analysis as a working hypothesis rather than proof of mechanism; enzyme kinetics and biophysical structural studies will be needed to confirm the precise interactions. Even so, the convergence of evidence is compelling: compound 12 inhibits tyrosinase at nanomolar-to-low-micromolar levels, suppresses elastase, collagenase, and hyaluronidase, scavenges free radicals, absorbs ultraviolet radiation, and spares human keratinocytes. As hyperpigmentation disorders spread with a warming climate and consumers demand safer alternatives to hydroquinone, this catechol-nitrophenyl coumarin offers a rare combination of potency, breadth, and preliminary safety. The next step—optimizing the lead into a candidate suitable for formulation and preclinical testing—will determine whether a single synthetic molecule can genuinely hold back the multiple clocks of skin aging at once.

Subject of Research: Design and biological evaluation of multitarget 3-arylcoumarin compounds inhibiting skin aging-related enzymes

Article Title: Multifunctional compounds for the treatment of skin diseases: synthesis, inhibition of skin aging-related enzymes, docking studies, and antioxidant activity

Article References: Floris, S., Era, B., Pintus, F., Fais, A., Novás, M., & Matos, M. J. (2026). Multifunctional compounds for the treatment of skin diseases: synthesis, inhibition of skin aging-related enzymes, docking studies, and antioxidant activity. Results in Chemistry, 31, Article 103941. https://doi.org/10.1016/j.rechem.2026.103941

Image Credits: AI Generated

DOI: 10.1016/j.rechem.2026.103941

Keywords: coumarin, tyrosinase, skin aging, hyperpigmentation, elastase, collagenase, hyaluronidase, antioxidant, molecular docking, sun protection factor, medicinal chemistry, keratinocytes