Phenolic acids

Phenolic phytochemicals can be categorized into three groups: phenolic acids, flavonoids, and stilbenes/lignans.

Phenolic acids refer to phenolic compounds that contain a single carboxylic acid group. They are a primary class of plant phenolic compounds and are found in various plant-based foods, including seeds, fruit skins, and vegetable leaves, with the highest concentrations. Plants produce these compounds to protect themselves from UV radiation, insects, viruses, and bacteria. Some plant species even produce phenolic compounds to hinder the growth of competing plants.

Strawberries primarily contain p-hydroxybenzoic acid and p-coumaric acid as their main phenolic acids, which are significant components of the berries. Chokeberries, on the other hand, are abundant in hydroxycinnamic acid derivatives, particularly chlorogenic acid and neochlorogenic acid.

Phenolic acids are also plentiful in cereals such as bread wheat, durum wheat, rye, hulless barley, and hull-less oat.

Based on their structure, phenolic acids can be classified into two distinct classes: derivatives of benzoic acid and derivatives of cinnamic acid. These compounds consist of a benzene ring bonded to either a carboxylic group (benzoic acids) or propenoic acid (cinnamic acids).

Examples of benzoic acid derivatives include p-hydroxybenzoic acid, salicylic acid, gallic acid, and ellagic acid. Common cinnamic acid derivatives include p-coumaric acid, caffeic acid, and ferulic acid.

Phenolic acids have been linked to the color, sensory qualities, and nutritional and antioxidant properties of foods. They are easily absorbed through the intestinal tract walls and offer health benefits to humans as antioxidants, aiding in the prevention of cell damage caused by free-radical oxidation reactions. Phenolic acids exhibit significantly higher in vitro antioxidant activity compared to well-known antioxidant vitamins. Although multiple mechanisms are involved, the primary mode of antioxidant activity is believed to be radical scavenging through hydrogen atom donation.
Phenolic acids