Where it appears
Common in onions, apples, berries, tea, and many other plants.
What is established
Pigmentation and antioxidant chemistry in plants is the appropriate plant-level description. Analytical identification and general flavonoid chemistry are more established than customer-facing outcome claims.
What remains uncertain
Well known nutritionally, but combustion or vapor exposure is not equivalent to eating a food source.
What shoppers should remember
Flavonoids are not cannabinoids or terpenes. Color alone cannot verify potency, effects, freshness, or quality. Product-specific composition requires reliable testing, and inhalation has route-specific risks.