Polyhydroxyphenols

Polyhydroxyphenols are a subset of phenolic compounds defined by the presence of two or more hydroxyl groups attached to an aromatic ring. Common members include the dihydroxybenzenes catechol (1,2-dihydroxybenzene), resorcinol (1,3-dihydroxybenzene), and hydroquinone (1,4-dihydroxybenzene), as well as trihydroxybenzenes such as pyrogallol (1,2,3-trihydroxybenzene). Benzoic acids with multiple hydroxy substituents, such as gallic acid (3,4,5-trihydroxybenzoic acid), are also encountered in discussions of polyhydroxyphenols.

These compounds occur widely in plants and plant-derived foods, where their multiple hydroxyl groups confer high reactivity and strong hydrogen-bonding capabilities. They are often responsible for color, flavor, and astringency in foods and beverages and contribute to the antioxidant capacity of plant extracts. Chemically, their multiple hydroxyl groups enable easy oxidation to quinones and allow metal chelation and the formation of polymeric networks upon oxidative coupling.

Applications and relevance: In industry and research, polyhydroxyphenols are used as antioxidants in foods and cosmetics and as reagents in analytical chemistry. They are also studied for biological activity, including radical scavenging and potential effects on signaling pathways. The diversity of structures—from simple dihydroxybenzenes to more complex polyhydroxy-substituted phenolics—gives rise to a range of physical and biological properties.

Safety and regulation: Some polyhydroxyphenols are hazardous in pure form, causing irritation, and their oxidation products can be reactive. In consumer products, their use is governed by safety standards and regulatory limits for specific compounds.