Subclass of Phenolics

Phenolic Acids

Simple phenol-ring acids and aldehydes — caffeic, rosmarinic, salicylic, and chlorogenic acid among them.

Overview

About Phenolic Acids

Phenolic acids are the simplest members of the phenolic family: a single aromatic ring carrying hydroxyl groups and a carboxylic acid. They divide into two series by the length of the side chain — the C6–C1 hydroxybenzoic acids and the C6–C3 hydroxycinnamic acids.

They are the most abundant polyphenols in the diet by mass, and they are also the metabolic crossroads of the whole phenolic world: larger polyphenols are broken down to phenolic acids in the gut, so these small molecules are often what actually circulates after a polyphenol-rich meal.

The Two Series

The distinction is worth holding, because the cinnamic series is by far the more abundant and more active:

Hydroxybenzoic acids (C6–C1): gallic, protocatechuic, vanillic, salicylic acid
Hydroxycinnamic acids (C6–C3): caffeic, ferulic, p-coumaric, sinapic acid

In plants these are rarely free. Caffeic acid bound to quinic acid gives chlorogenic acid; two caffeic acids give rosmarinic acid; ferulic acid cross-links cell-wall polysaccharides.

Where Phenolic Acids Occur

Near-universal, with some conspicuous concentrations:

Coffee

chlorogenic acid, the largest single dietary source

Rosemary, sage, lemon balm and the mint family

rosmarinic acid

Whole grains and cereal bran

ferulic acid

Berries and tea

gallic and ellagic acid

Willow and meadowsweet

salicylates

Pharmacological Importance

The best-known member barely reads as a plant compound any more: salicylic acid from willow bark is the direct structural ancestor of aspirin, and the whole non-steroidal anti-inflammatory class descends from it.

Rosmarinic acid carries much of the anti-inflammatory and anti-allergic activity of the Lamiaceae herbs. Chlorogenic acid slows intestinal glucose absorption and is the compound behind green-coffee-extract metabolic claims. Ferulic acid is a potent lipid-phase antioxidant and a mainstay of photoprotective skincare formulation.

Toxicity & Safety

As a class these are gentle, heavily consumed dietary compounds with no meaningful toxicity at food-level intake.

The salicylates are the exception to flag: they carry the aspirin cautions in miniature — gastric irritation, antiplatelet effect, salicylate sensitivity, and the Reye's-syndrome concern that keeps salicylate herbs away from febrile children.

Constituents

All Phenolic Acids

84 total Filter phenolic acids

3,5-Dicaffeoylquinic Acid 5 herbs 4-Hydroxybenzoic acid 1 herb 4-Hydroxybenzyl Alcohol 1 herb 4-Hydroxycinnamic acid 1 herb 4-Methoxyphenol 1 herb 4,5-Dicaffeoylquinic Acid 3 herbs

Anisic acid 2 herbs · 1 supp Anisic aldehyde 1 herb

Barbatic acid 1 herb Benzoic acid 1 herb

Caffeic acid 40 herbs Caffeotannic acid 1 herb Caffeoyl quinides 1 herb Caffeoyl-malic acid 1 herb Caftaric Acid 2 herbs Catechol 2 herbs Catechols 1 herb Chebulic acid 1 herb Chlorogenic acid 39 herbs Cichoric Acid 2 herbs Cinnamic acid 2 herbs Cohumulone 1 herb Colupulone 1 herb Coumaric acid 1 herb

Open in filterable index

Source Plants

Herbs Containing Phenolic Acids

106 herbs

Plants in the materia medica documented to carry phenolic acids, with the compounds each one is listed for. The bar counts how many DISTINCT phenolic acids are on record for a plant, relative to the best-documented — it measures breadth of record, not potency, so a plant with one well-studied compound can outrank a richer source that has simply been analysed less. Where a measured concentration is on record it is quoted inline; most entries have none yet.