Changes in phenolic composition of wines submitted to in vitro dissolution tests

Wine is an important source of dietary antioxidants, due to its content of phenolic compounds. These compounds may be degraded in the gastrointestinal tract before absorption. A hydroalcoholic standard solution containing 14 phenolic compounds and 25 wines (red, white and Sherry wines) were submitted to a dissolution test employing gastric and intestinal fluids according to The United States Pharmacopeia conditions. Concentration of each phenol was determined, before and after the treatments, by high-performance liquid chromatography with a photodiode array detector. In the standard solution, phenolic acids were rather stable in gastric and intestinal media. Flavonoids were affected most. When wines were submitted to this test, gallic acid, caffeic acid, catechin and quercetin increased in concentrations while resveratrol (trans-, cis- and their glucosides), caffeoyltartaric acid and ethyl gallate resisted gastric and intestinal media.