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

The study, led by Sarah Boukhalkhal of Amar Telidji University in Laghouat, Algeria, set out with three interlocking goals: to isolate and chemically characterize lycopene from tomato, to quantify its antioxidant and antimicrobial potency in vitro, and to embed the purified pigment into a stable emulgel formulation suitable for topical application. Each stage of the work built on the previous one, moving from bench chemistry to formulation science in a single pipeline, and the results collectively argue that lycopene deserves a place among the serious candidates for plant-based sun protection.

Purification and identification came first. The researchers used thin-layer chromatography to separate the pigment from the crude tomato extract, then confirmed its identity with Fourier-transform infrared spectroscopy and ultra-high-performance liquid chromatography coupled to electrospray ionization mass spectrometry. These techniques revealed the characteristic spectral fingerprint of polyene carotenoids, the long conjugated double-bond chains that give lycopene its deep red color and, crucially, its ability to absorb light and neutralize reactive molecules. The conjugated polyene system is the molecular secret behind everything that followed: it allows the molecule to quench singlet oxygen and free radicals with remarkable efficiency, a property that has long made lycopene one of the most studied carotenoids in biomedical literature.

The antioxidant performance of the purified compound was striking. In the DPPH free-radical scavenging assay, the purified lycopene achieved an IC50 value of 3.2 micrograms per milliliter, meaning that a very small concentration was enough to neutralize half of the free radicals in the test system. Lower IC50 values indicate stronger antioxidant activity, and this figure compared favorably with reference antioxidant compounds. The team also measured the pigment’s reducing power, which reflects its capacity to donate electrons and thereby terminate radical chain reactions, and found it superior to the reference compounds used for comparison. In a third test, the beta-carotene and linoleic acid bleaching system, which models the protection of lipids against peroxidation, the lycopene again demonstrated a strong protective effect. Together, these three complementary assays paint a consistent picture of a molecule that intercepts oxidative damage through multiple chemical mechanisms rather than a single pathway.

The antimicrobial results may prove equally consequential. Lycopene showed significant activity against a panel of skin-relevant pathogens, including Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, and Micrococcus luteus, as well as the yeast Candida albicans and several Gram-negative bacteria responsible for skin and soft-tissue infections. The activity against MRSA is particularly noteworthy given the global crisis of antibiotic resistance and the urgent need for topical agents that can help manage colonized or infected skin without contributing further to resistance. Previous studies have suggested that lycopene disrupts microbial cytoplasmic membranes and can trigger reactive oxygen species production and mitochondrial dysfunction in Candida albicans, and the new findings align with that mechanistic picture, although the authors of the current study did not set out to resolve the mechanism themselves.

With the purified pigment validated on two fronts, the team turned to formulation. An emulgel, a hybrid dosage form that combines the hydration and spreadability of an emulsion with the cooling, non-greasy feel of a gel, was chosen as the vehicle. The researchers prepared several formulations containing different amounts of lycopene and subjected each to physical stability testing, pH measurement, viscosity analysis, and homogeneity assessment. The standout was a formulation designated F1, containing 0.01 grams of lycopene, which remained physically stable and displayed an appropriate pH and viscosity for skin application, along with a homogeneous consistency. These parameters matter enormously in practice: a sunscreen that separates in the tube, irritates the skin because of an unbalanced pH, or feels unpleasant to apply will fail commercially no matter how active its ingredients are.

The photoprotection data were the headline result. Using an in vitro spectrophotometric method, the team calculated the sun protection factor of the F1 emulgel and obtained a value of 38.8, which the authors describe as comparable to commercial SPF 50+ sunscreens. The in vitro SPF determination works by measuring the absorbance of the formulation across the ultraviolet spectrum and applying a mathematical weighting that accounts for the solar irradiance spectrum and the erythemal action spectrum of human skin. While in vitro values do not automatically translate to in vivo performance on human volunteers, a result of this magnitude from a single natural pigment, without synthetic UV filters, is remarkable and points to the strong intrinsic UV-absorbing capacity of lycopene’s conjugated double-bond system.

The broader scientific context strengthens the case. Lycopene has long been recognized as one of the most efficient biological singlet oxygen quenchers known, a distinction established in landmark work from the late 1980s. Epidemiological and dietary studies have associated lycopene-rich tomato products with reduced sensitivity to ultraviolet-induced erythema, and cell culture experiments have shown that lycopene protects human skin fibroblasts from UVA damage. What the new study adds is the formulation step: converting a well-documented biological antioxidant into a physically stable, topically applicable product whose photoprotective performance can be quantified against commercial benchmarks. Earlier attempts at lycopene emulgels and microemulsions have explored similar territory, but the combination of purified compound, rigorous chemical characterization, antimicrobial screening against resistant strains, and high SPF measurement in a single study is unusual.

The implications reach beyond sunscreens. A single plant-derived ingredient that offers antioxidant defense, antimicrobial action against both resistant bacteria and fungi, and measurable UV protection addresses several cosmetic and dermatological needs at once. This multifunctionality could simplify product formulations, reduce reliance on synthetic preservatives and chemical UV filters, and appeal to the fast-growing market for natural and sustainable skincare. The researchers caution, appropriately, that further research and applications are needed before such a product reaches consumers. Clinical trials on human skin, long-term stability studies under real-world storage conditions, photostability testing to confirm that the lycopene itself does not degrade under sunlight, and safety and irritation assessments would all be required by regulators before any SPF claim could appear on a label.

Nevertheless, the study is a compelling proof of concept that the humble tomato contains a molecule capable of doing serious work on human skin. The research was conducted at the Laboratory of Fundamental Sciences of Amar Telidji University and in collaboration with the LAQV-REQUIMTE research unit at the University of Aveiro in Portugal, and it received no external funding. As the cosmetics industry searches for credible plant-based alternatives to synthetic UV filters, and as dermatologists look for new topical tools against resistant skin pathogens, lycopene has now demonstrated in a single, carefully controlled study that it can plausibly serve both masters. The next chapter, moving from the spectrophotometer to human skin, will determine whether the tomato’s red pigment can graduate from promising laboratory candidate to genuine ingredient on the sunscreen shelf.

Subject of Research: Lycopene-based emulgel formulation from tomato with antioxidant, antimicrobial and photoprotective properties

Article Title: Antioxidant, antimicrobial and photoprotective activities of a lycopene-based emulgel from Solanum lycopersicum

Article References: Boukhalkhal, S., Elhouiti, F., Zegrir, A., Saidat, B., Pinto, D. C. G. A., Silva, A. M. S., Válega, M. S. G. A., Dakmoussi, B. I., Derreche, Y., & Yousfi, M. (2026). Antioxidant, antimicrobial and photoprotective activities of a lycopene-based emulgel from Solanum lycopersicum. Plant Biosystems, 160(4), Article 222. https://doi.org/10.1007/s44473-026-00226-1

Image Credits: AI Generated

DOI: 10.1007/s44473-026-00226-1

Keywords: lycopene, tomato, Solanum lycopersicum, emulgel, sun protection factor, photoprotection, antioxidant activity, antimicrobial activity, MRSA, Candida albicans, carotenoids, natural skincare