anthocyanidins

Anthocyanidins are a class of flavonoid compounds that represent the aglycone (non-sugary) forms of anthocyanins, the pigments responsible for red, purple, and blue colors in many fruits, vegetables, and flowers. Structurally, they are flavylium cations based on a 2-phenylchromenylium backbone and differ in hydroxyl and methoxy substitutions on the B ring. Common anthocyanidins include cyanidin, delphinidin, pelargonidin, petunidin, peonidin, and malvidin. In plants, anthocyanidins are typically glycosylated to form anthocyanins, which are more stable and water-soluble pigments stored in vacuoles.

Anthocyanidins occur widely in crops and ornamental plants, contributing colors ranging from red to blue. They are especially abundant in berries, grapes, cherries, red onions, and red cabbage. Their color expression is influenced by pH, metal ions, and co-pigments. Biosynthetically, they arise from the phenylpropanoid pathway through the flavonoid biosynthetic route, with glycosylation and acylation modifying stability, hue, and solubility.

Stability and metabolism: anthocyanidins are sensitive to pH and light, and they can degrade or change color under neutral or alkaline conditions. In humans, dietary anthocyanins are partially hydrolyzed to anthocyanidins in the gut, and both aglycones and glycosides undergo further metabolism, including glucuronidation and sulfation. Bioavailability is typically modest and highly variable, influencing physiological effects.

Health interpretation: research has explored antioxidant, anti-inflammatory, and cardiometabolic benefits, but clinical evidence is inconsistent and no formal health claims are established. Anthocyanidins are considered phytochemicals of interest with potential benefits, warranting further high-quality studies.