pcoumaric

p-Coumaric acid, also known as 4-hydroxycinnamic acid, is a hydroxycinnamic acid with the formula C9H8O3. It features a phenyl ring bearing a para hydroxyl group and a trans-propenoic acid side chain. It is one of the most common hydroxycinnamic acids encountered in plants and plant-derived foods.

Occurrence and role: p-Coumaric acid occurs in free form and as esters in many plant tissues, including fruits, vegetables, grains, and wines. It is a key intermediate in the plant phenylpropanoid pathway, derived from phenylalanine by phenylalanine ammonia-lyase to cinnamic acid, then hydroxylated by cinnamate 4-hydroxylase to form p-coumaric acid. It is activated to p-coumaroyl-CoA by 4-coumarate-CoA ligase, linking it to the biosynthesis of lignin, suberin, and a range of phenolic polymers. It also serves as a substrate for chalcone synthase in flavonoid biosynthesis and for stilbene synthase in stilbenes such as resveratrol, with p-coumaroyl-CoA acting as the starter unit for these compound classes.

Properties and applications: p-Coumaric acid possesses antioxidant activity in vitro and is widely used as a reference compound in analytical chemistry and plant metabolomics. In foods and beverages, it contributes to the polyphenol profile that influences color, flavor, and potential health properties.

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