Bidirectional regulation of heterocyclic amines by flavonoids: insights from flavonoid amination using dihydromyricetin and baicalein.

Heterocyclic amines (HCAs) are carcinogenic contaminants formed during meat thermal processing, and the traditionally recognized inhibitory effects of flavonoids on HCA formation remain controversial. Dihydromyricetin (DMY) and baicalein (BAI) both exhibited dose-dependent bidirectional effects on PhIP formation in a PhIP chemical model. At low concentrations (DMY 125-250 μM, BAI 125-1000 μM), PhIP levels gradually increased to nearly 210% and 300% of control, respectively, mainly driven by amination-related reactions of flavonoid thermal degradation products that promoted phenylacetaldehyde accumulation. At high concentrations (≥2000 μM), PhIP was suppressed to <50% (DMY) and <20% (BAI) of control via potent radical scavenging and phenylacetaldehyde trapping. The bidirectional regulation may be governed by a dynamic balance between amination-driven promotion and the dual inhibitory pathways for PhIP formation. This study explains how flavonoids lead to contradictory effects on HCA formation in cooked meat and provides a mechanistic foundation for their application.