DPPH Assay

The DPPH assay provides a quantitative measure of a product’s or ingredient’s ability to scavenge free radicals. It is used during formulation development, ingredient evaluation, stability programmes, and to generate supporting data for antioxidant-related claims.

What the DPPH assay measures

DPPH (2,2-diphenyl-1-picrylhydrazyl) is a stable free radical that produces a deep violet colour in solution and absorbs strongly at approximately 517 nm. When an antioxidant donates a hydrogen atom or electron, the radical is reduced and the solution decolourises. The decrease in absorbance is proportional to the radical-scavenging activity present.

Results are typically expressed as percentage inhibition, IC₅₀, or Trolox equivalents, giving a clear numerical indication of antioxidant capacity.

Applications in product development

• Formulation optimisation — compare the contribution of different ingredient combinations or concentrations to overall antioxidant activity.
• Ingredient screening — assess the radical-scavenging potential of candidate actives before inclusion in a finished product.
• Stability monitoring — track changes in antioxidant capacity over time or under accelerated storage conditions.
• Claims support — generate quantitative data that can underpin statements relating to antioxidant protection or free-radical scavenging.
• Benchmarking — position a product relative to competitor formulations.

Relevance to regulatory files and claims

Quantitative antioxidant data can form part of the supporting evidence in the Product Information File. While not a mandatory requirement under Annex I of Regulation (EC) No 1223/2009 in the same way as microbiology or stability, analytical results of this type contribute to the overall dossier reviewed by the safety assessor and, where necessary, by competent authorities. They also assist in the substantiation of performance claims.

The process

1. Submit product or ingredient samples.
2. The assay is performed by our laboratory staff using validated spectrophotometric methods.
3. A report is issued detailing the measured antioxidant capacity. Interpretation is available on request.
4. Data can be used for formulation decisions or claim substantiation.

Why Oxford Biosciences

• Conducted entirely in-house under the Head of Laboratory Sciences; analytical work is never outsourced.
• Results integrate directly with CPSR preparation where required.
• Flexible scoping for single products, multiple formulations, comparative studies, or time-series stability work.
• Clear numerical reporting suitable for both technical files and marketing use.