Anthocyanin (Flavonoid)

Anthocyanins are water-soluble polyphenolic flavonoid pigments, not macronutrients themselves, but bioactive micronutrients found in plant foods. Pure anthocyanin content varies by source: blueberries contain 25-495 mg/100g fresh weight, blackberries 83-326 mg/100g, black elderberries 450-1,800 mg/100g, black currants 130-400 mg/100g, and red/purple grapes 6-600 mg/100g. As isolated compounds or supplements, they are typically standardized to 25-50% anthocyanin content by weight. Chemically, they exist as glycosides (anthocyanins) with sugar moieties attached to anthocyanidin aglycones; the six most common aglycones are cyanidin, delphinidin, malvidin, pelargonidin, peonidin, and petunidin. Cyanidin-3-glucoside is among the most studied individual forms. Bioavailability is notably low and highly variable: oral bioavailability is estimated at 0.1-1.8% of ingested dose in most human studies, with peak plasma concentrations of 1-100 nmol/L reached within 0.5-2 hours post-ingestion. Bioavailability is influenced by food matrix (juice vs. whole fruit), gut microbiome composition (which extensively metabolizes anthocyanins into phenolic acid metabolites such as protocatechuic acid, vanillic acid, and hippuric acid), pH stability (rapidly degraded at neutral to alkaline pH), and co-ingestion with dietary fats or proteins. Colonic microbial metabolites may account for a significant portion of biological activity. Anthocyanins contain no protein, fat, or fiber as isolated compounds. They are calorie-negligible in supplemental form. No significant vitamin or mineral content is inherent to the anthocyanin molecule itself, though whole-food sources providing anthocyanins also supply vitamin C, manganese, and dietary fiber.