Phenolic Compounds

Phenolic compounds are the reason peat bogs preserve everything — from fallen branches to 2,000-year-old human bodies. They’re also a major reason peat works on skin.

Phenolics are a broad class of organic molecules built around an aromatic ring with one or more hydroxyl (–OH) groups attached. In peat, they come from the lignin and tannins of the original plant material — primarily sphagnum moss — and are transformed during decomposition. They exist both as free molecules and woven into the structure of humic acids and fulvic acids.

What phenolics do

Neutralise free radicals. The hydroxyl groups on phenolic rings donate hydrogen atoms to unstable free radical molecules, neutralising them before they can damage cell membranes, collagen, or DNA. This is the same antioxidant mechanism behind vitamin C, green tea polyphenols, and resveratrol in wine — peat just delivers it through a different matrix. HPLC analysis has identified at least 8 distinct phenolic acids in peat extracts (Tarnawski 2006).

A rat study found that sphagnum-derived phenolics activate the Nrf2 pathway — the body’s master antioxidant defence switch — reducing oxidative stress markers in living tissue (Laorodphun 2024). This suggests the antioxidant effect is not just passive radical scavenging but an active upregulation of the body’s own protective systems.

Kill microbes. Phenolics contribute to peat’s antimicrobial environment. This is why peat bogs don’t rot — the phenolic compounds suppress bacterial and fungal growth in the surrounding water. On skin, this translates to activity against the bacteria and yeasts involved in acne, dandruff, and fungal infections (Painter 1991).

Tighten and tone. Phenolics precipitate proteins on the skin surface — a process called astringency. The result is temporary pore tightening and a firmer skin texture. This is most noticeable in face masks, where the immediate “tightening” sensation comes directly from phenolic-protein interaction (Scalbert 1991).

Types in peat

Peat contains a diverse range of phenolic subclasses: simple phenols, hydroxycinnamic acids, flavonoids, tannins (both condensed and hydrolysable), and lignin-derived phenolics. Sphagnum peat is particularly rich in sphagnum acid (p-hydroxyphenylacetic acid), a distinctive compound derived from the moss itself.

The phenolic profile of peat changes with depth and humification. In younger, less decomposed layers, free phenolics dominate. As peat ages, phenolics are progressively incorporated into the humic substance matrix — becoming part of the humic and fulvic acid molecules rather than existing independently.

Why this matters for skin

Phenolics are the structural backbone of peat’s three most cosmetically relevant mechanisms: antioxidant protection against skin aging, antimicrobial action for acne and scalp conditions, and astringent toning for visible pore refinement. Every peat product — from a bath to a serum — delivers phenolics as part of its chemical package.