Diacetylated and acetone-conjugated flavan-3-ols as potent antioxidants with cell penetration ability

•Acetylated or acetone-conjugated flavan-3-ols were prepared.•The 3, 5 or 3, 7-O-diacetyl flavan-3-ols have high cell penetration ability.•The diacetyl flavan-3-ols released free flavan-3-ols in cells.•Acetone conjugates of flavan-3-ols entered into cells in intact form.•The derivatives protected oxidative hemolysis more effectively than flavan-3-ols.