Compound Class

Organic Acids

Small plant acids that shape flavor, pH, and metabolism — malic, formic, angelic, and related acids.

Overview

What Are Organic Acids?

Organic acids are the small, non-aromatic molecules carrying one or more carboxylic-acid (–COOH) groups — the sour, tart principles of fruits and saps.

Their acidity comes directly from those carboxyl groups, which readily give up a proton in solution. Most are ordinary intermediates of plant metabolism, which makes them close to ubiquitous.

Where Organic Acids Occur

The acids of the Krebs cycle turn up in virtually every living tissue, while others accumulate in specific organs to set fruit sourness and buffer cellular pH:

Apples

malic acid

Citrus fruit

citric acid

Grapes

tartaric acid

Valerian

valeric and isovaleric acid

Nettles and ants

formic acid

Their concentration is a large part of what gives a fruit or sap its characteristic sharpness.

Defining the Class

The boundary here is structural. The class gathers the simple aliphatic acids — malic, citric, tartaric, formic, valeric, angelic, gluconic, glycolic and their kin — while the ring-bearing phenolic acids and the long-chain fatty acids are classified separately.

In short: if an acid is neither aromatic nor a fatty acid, it belongs here.

Pharmacological Importance

The group contributes flavor, metal chelation and gentle exfoliation or astringency rather than strong pharmacology. Malic and citric acid are everyday food additives, and the alpha-hydroxy acids are used topically to loosen dead skin.

Some carry more specific associations — the valeric acids of valerian are part of that herb's sedative reputation, and citric acid's ability to bind minerals is used to improve the absorption of mineral supplements.

Toxicity & Safety

The group is overwhelmingly benign and largely food-grade.

The caveats are those of concentration and irritancy rather than systemic poisoning: formic acid delivers the sting of nettles and ant bites, and oxalic acid can irritate tissues and bind calcium, which is why high-oxalate plants such as rhubarb leaf are avoided.

Constituents

All Organic Acids

29 total Filter organic acids

Open in filterable index

Source Plants

Herbs Containing Organic Acids

25 herbs

Plants in the materia medica documented to carry organic acids, with the compounds each one is listed for. The bar counts how many DISTINCT organic 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.