The researchers used the classic imiquimod model of psoriasis, in which daily application of an immune-stimulating cream to shaved mouse skin triggers scaly, red, thickened lesions that closely mirror human disease. Imiquimod works by activating toll-like receptors 7 and 8, unleashing a cascade of inflammatory cytokines, and it also acts directly on itch-sensing nerve channels. Fifty-six mice were divided into seven groups: a healthy control, an untreated disease model, a plain gel base, the corticosteroid clobetasol propionate as a benchmark, and three experimental groups receiving celecoxib emulgel, diallyl trisulfide emulgel, or a combination of both. Treatment began on day eight and continued for a week, with all assessments performed by blinded observers in line with ARRIVE guidelines.

The results were striking. Mice treated with imiquimod alone developed severe lesions, with cumulative Psoriasis Area and Severity Index scores climbing to 4.6 while controls stayed at zero. The plain gel base helped somewhat — an expected emollient effect — but the active treatments cut scores far more deeply: celecoxib brought the score down to 1.75, diallyl trisulfide to 1.4, and the combination to 1.9, all statistically indistinguishable from the gold-standard corticosteroid. Histological examination told the same story. Where imiquimod-treated skin showed thickened epidermis, parakeratosis, Munro microabscesses, and dense lymphocytic infiltration, treated skin retained near-normal architecture, with epidermal thickness reduced by more than half in all three active groups.

Perhaps the most patient-relevant finding concerned itch. Scratching is not merely a nuisance in psoriasis — it can trigger the Koebner phenomenon, in which new lesions appear at sites of skin trauma, creating a vicious cycle. Imiquimod-treated mice scratched nearly four times more often than controls over a thirty-minute observation window. Celecoxib cut scratch bouts by 66 percent, diallyl trisulfide by 77 percent, and the combination by 70 percent, matching the corticosteroid. Skin serotonin, a key itch mediator that also drives keratinocyte proliferation and lymphocyte activation, fell by up to 56 percent — and the combination actually outperformed the steroid on this measure, reducing serotonin 23 percent more than clobetasol did.

Underneath these visible improvements, the team mapped a coherent molecular mechanism. Imiquimod inflated the interleukin-23/interleukin-22/interleukin-19/interleukin-17 axis — the canonical psoriasis pathway — raising skin IL-23 nearly twofold, IL-22 more than threefold, and serum IL-17 almost fourfold. Both compounds, alone and together, suppressed every node of this axis, with the combination reducing IL-17 by 68 percent. A Bliss independence analysis revealed that the combination acted synergistically on IL-23, the master cytokine that sustains Th17 cells, the immune population widely blamed for driving psoriatic inflammation.

The drugs also converged on the interleukin-6/JAK2/STAT3 signaling cascade, a pathway targeted by several approved psoriasis drugs. Imiquimod raised serum IL-6 nearly fivefold and ear JAK2 and STAT3 protein levels five- to sevenfold. The combination therapy knocked these back by 68, 64, and 71 percent respectively — beating the corticosteroid by 26 to 40 percent on each measure. This matters because JAK/STAT signaling has been directly linked to cytokine-induced itch, and JAK inhibitors relieve pruritus in psoriasis patients. The authors note a limitation: they measured total protein rather than the phosphorylated, active forms of JAK2 and STAT3, so follow-up work with phospho-specific assays is planned.

Inflammation beyond the cytokine axis also subsided. Interferon-gamma and tumor necrosis factor-alpha, both elevated by imiquimod, fell by up to 51 and 64 percent respectively under combination treatment, and myeloperoxidase — an enzyme marker of neutrophil infiltration that correlates with disease severity — dropped by half. Immunohistochemistry confirmed that CD4-positive and CD8-positive T-cell infiltration into skin, which surged after imiquimod exposure, was significantly reduced by all three treatments. Pearson correlation analysis strengthened the biological story: every inflammatory marker measured correlated strongly and positively with both PASI scores and scratch counts, reinforcing their potential as biomarkers of disease activity.

One of the more intriguing findings concerned the spleen. Imiquimod increased absolute spleen weight by 88 percent, reflecting extramedullary hematopoiesis and systemic immune activation — evidence that even a skin-limited trigger reverberates through the whole body. Celecoxib, diallyl trisulfide, and their combination all reduced spleen weight by roughly a third, and histology showed the combination preserved near-normal splenic architecture, with only minimal expansion of lymphoid follicles. Notably, the corticosteroid group showed the least splenic recovery, alongside the well-documented skin-thinning and hair-follicle atrophy that steroids cause — adverse effects the experimental emulgels did not produce.

The rationale for pairing these two particular molecules is elegant. Celecoxib, a selective COX-2 inhibitor, suppresses prostaglandin E2, a mediator elevated in psoriatic blister fluid that fuels both inflammation and itch; it also independently dampens IL-6-driven STAT3 activation. Diallyl trisulfide is a slow-releasing hydrogen sulfide donor derived from garlic, and serum hydrogen sulfide is known to be depleted in psoriasis patients in proportion to disease severity. Slow-release donors mimic the body’s natural sustained hydrogen sulfide production better than inorganic salts, and related donors have already eased psoriasis-like disease in mice by curbing neutrophil recruitment and pruritus. Hydrogen sulfide–NSAID hybrid molecules are an active research frontier precisely because pairing the two mechanisms lowers toxicity while boosting anti-inflammatory effect.

The authors are careful about scope. This was a single-dose screening study in an animal model, with no pharmacokinetic, skin-deposition, or long-term safety data yet, and no solvent-matched vehicle control for the dimethylformamide carrier. Equivalence to corticosteroid therapy cannot be claimed from this design. But the convergence of evidence — PASI relief, itch suppression, histological normalization, spleen protection, and coordinated damping of the IL-23/IL-17 and IL-6/JAK2/STAT3 cascades, all achieved with topically applied, inexpensive, orally familiar compounds — makes a compelling case for the next step: head-to-head clinical comparison against clobetasol in patients with early psoriasis. If the mouse results translate, relief for the 60 to 90 percent of patients who itch might come not from a new biologic, but from a garlic extract and an old painkiller rubbed into the skin.

Subject of Research: Topical celecoxib and diallyl trisulfide emulgels against imiquimod-induced psoriasis in BALB/c mice

Article Title: Celecoxib or diallyl trisulfide topical emulgels, alone or in combination, reduce pruritus and inflammatory cascades in a BALB/c mouse model of imiquimod-induced psoriasis

Article References: Kamel, M. M., Zaki, H. F., Saleh, R. A., Henry, S. R., Ibrahim, M. K., Mofreh Bakr, M., Abouhussein, D. M. N., & Rabie, M. A. (2026). Celecoxib or diallyl trisulfide topical emulgels, alone or in combination, reduce pruritus and inflammatory cascades in a BALB/c mouse model of imiquimod-induced psoriasis. Pharmacia, 73, Article e205623. https://doi.org/10.3897/pharmacia.73.e205623

Image Credits: AI Generated

DOI: 10.3897/pharmacia.73.e205623

Keywords: psoriasis, celecoxib, diallyl trisulfide, imiquimod mouse model, IL-23/IL-17 axis, JAK2/STAT3, pruritus, hydrogen sulfide donor, emulgel, BALB/c mice, inflammation, clobetasol

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