Not all antioxidants work in the same way, and not every antioxidant claim is supported by the same level of evidence. A single test result can suggest strong antioxidant activity while revealing very little about how an ingredient works, whether it performs in a formulation, or whether it remains active inside living cells. For product developers, these differences can influence ingredient selection, formulation strategy and the strength of any supporting claims.
Our antioxidant testing portfolio is designed to answer these questions in a logical sequence. We begin with rapid chemical assays that establish antioxidant capacity and identify the underlying mechanism of action before progressing to cell-based testing that demonstrates activity in a biologically relevant environment. This staged approach provides a more complete understanding of antioxidant performance while helping R&D teams focus resources on the most promising candidate materials.
Two ingredients can return similar antioxidant scores and behave completely differently in a formulation. Most antioxidant assays measure a single mechanism, and molecules neutralise free radicals by more than one: principally single electron transfer (SET) and hydrogen atom transfer (HAT). A material that scores well on one pathway may be weak on the other, which is invisible if you only ran one test.
That distinction matters more than it used to. Antioxidant claims are now common enough across price tiers that the claim alone does little to differentiate, and market analysis suggests the value is shifting toward products with validated evidence behind them rather than the claim in isolation [1]. We run antioxidant testing in two stages, and the order they come in is doing real work.
Capacity and mechanism
Our screening tier runs ABTS, CUPRAC and ORAC concurrently. Each assay probes a different aspect of antioxidant behaviour, and running all three together produces a profile rather than a single number.
ABTS measures the ability to quench the ABTS radical cation, predominantly via single electron transfer with a minor HAT contribution. CUPRAC measures reducing capacity through the formation of a coloured copper-neocuproine complex. ORAC measures peroxyl radical scavenging, a hydrogen atom transfer assay considered more physiologically relevant than purely electron-transfer methods because peroxyl radicals are implicated in lipid oxidation and skin ageing.
Read together, the pattern indicates mechanism. Low CUPRAC with moderate ABTS and high ORAC points to a HAT-dominant antioxidant. High CUPRAC with moderate ABTS and low ORAC points to SET-dominant. Balanced values across all three indicate a mixed mechanism.
Results are expressed as Trolox Equivalent Antioxidant Capacity (TEAC) in µM, allowing direct comparison against the Trolox standard and against industry benchmark ingredients. Test items are evaluated at six concentrations, from neat through to formulation-relevant levels, alongside a Trolox standard curve and vehicle controls. Statistical significance is determined using a two-tailed Student’s t-test against vehicle controls.
What happens in cells
Chemical assays establish what a molecule can do. They can’t show whether it does the same thing once it has to get into a cell.
The OxiSelect™ method exposes human epidermal keratinocytes, cultured in animal-product-free conditions, to a range of concentrations of the active or product. Working in whole cells accounts for pH, cellular uptake and metabolism, and the method captures antioxidant contributions from all major reactive oxygen species: peroxides, superoxides, hydroxyl radicals and singlet oxygen. Quercetin serves as the positive control.
The test is based on intracellular conversion of DCFH to its fluorescent metabolite DCF. Antioxidants inhibit that reaction, reducing the fluorescence observed. Fluorescence is monitored over time and results are plotted to show any dose-dependent antioxidant potential.
Actives can be tested alone or in combination. Combination testing is where synergies show up, and where they don’t. Two ingredients that both perform individually may add nothing to each other, or one may reduce the effect of the other. Raw material data won’t tell you which.
The method suits ingredients and formulations with sufficient aqueous solubility in cell culture medium. Claims supported at this level include antioxidant, anti-pollution and anti-ageing.
Why the order matters
The screening tier is cell-free, quick and takes a smaller sample. That makes it the right place to start when you have several candidate materials and no strong reason to prefer one.
It narrows the field on two counts. It tells you which materials have meaningful capacity, and it tells you how they achieve it. Two ingredients with comparable TEAC values but opposite mechanisms are not interchangeable in a formulation, and that’s a useful thing to know before you commit to one.
The cell-based work is then concentrated on the materials that came through, and on the combinations you actually want to build. Rather than running every candidate through the more involved method, you’re running the shortlist. If a material doesn’t perform at the screening stage, you find that out early, on a small sample, with the option to go back to the drawing board while it’s still cheap to do so.
For an R&D team working through a set of candidate actives, that sequencing turns a broad question into a narrow one before the expensive part begins.
All testing is conducted in our GLP-accredited laboratory using animal-product-free methods. These are non-regulatory tests designed for ingredient screening, product development and claims support.
If you’re working on an antioxidant, anti-pollution or anti-ageing claim, we’re happy to talk through what would suit.
Email info@x-cellr8.com or call +44 (0)1925 607 134.
Reference
[1] Fact.MR (2026). Antioxidant-Rich Skincare Market Size, Share & Forecast to 2036, 4 March 2026.
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