Resveratrol

A polyphenol stilbenoid produced by grapes, knotweed (Polygonum cuspidatum, the primary commercial source), and a handful of other plants as a phytoalexin defence against fungal infection. Topically it operates across three layers: as a direct antioxidant (the phenolic structure quenches peroxyl and hydroxyl radicals), as a sirtuin-1 activator (the longevity-pathway hook — SIRT1 deacetylates and modulates p53, NF-κB, and FOXO signalling), and as a photoprotective UVB-absorbing chromophore that also reduces UVA-induced ROS in fibroblasts. The trans-isomer is the active form; cis-resveratrol and the oxidised product (resveratrol-glycol) are inactive and accumulate in poorly packaged formulations.

0.5–1% (trans-isomer; opaque packaging mandatory)

Effective at 0.5–1% in serums; trans-resveratrol is the active form. Light- and oxygen-sensitive — opaque packaging required. pH 5–6. Caudalie's airless pumps are a category-defining choice.

Cis-resveratrol (the inactive isomer) and degraded products are common formulation failures — supplier and packaging matter enormously.

The longevity-supplement origin story is a recurring overreach — most landmark resveratrol research (the Sinclair/Howitz SIRT1 papers) is oral and at concentrations that do not translate to topical pharmacology. Stability is the formulation honesty issue: trans-resveratrol oxidises rapidly in light and air, and a yellow-brown serum has lost much of its claimed activity. Caudalie's airless pump packaging is the category reference for a real reason.

Caudalie's prestige category-defining hero — and a recurring tentpole of the longevity-skincare conversation. The molecule earns a place in stacked antioxidant systems; the standalone 'reverses aging' framing inherits credibility from supplement-industry overclaim and should be read as topical antioxidant, not topical sirtuin therapy.