Açaí seed and grape rachis extracts are sources of procyanidins and flavan-3-ols.
Açaí seed and grape rachis could be explored as antioxidants for lipid-rich foods.
Extracts were antioxidant or prooxidant in soybean oil, depending on the concentration.
High hydrophilic/lipophilic antioxidant ratio resulted in synergistic effects.
Eighteen procyanidins and resveratrol were identified in açaí seed.