Phenolics from Whole Grain Oat Products as Modifiers of Starch Digestion and Intestinal Glucose Transport.

ABSTRACT

Four oat varieties and three product forms (porridge, cereal, and snack bar) were assessed to determine the impact of oat phenolics on starch digestibility and intestinal glucose transport. α-Amylase activity was enhanced by 20 GAE µM (gallic acid equivalent) of phenolics extracted from oat (96.7-118%, p < 0.05), while it was modestly inhibited at 500 GAE µM (83.0-95.4%). Maltose hydrolysis was reduced (49.6-82.4%, p < 0.05), albeit with high IC50 values (500-940 GAE µM). Free and bound oat phenolic extracts dose-dependently attenuated transport of d-glucose-1,2,3,4,5,6,6-d7 by Caco-2 monolayers over 60 min. Oat foods were then subjected to a coupled in vitro digestion/Caco-2 intestinal cell model to determine relevance to whole food systems. Digestive release of glucose was similar among products; however, glucose transport was significantly reduced from digesta of GMI 423 porridge and puffed cereal by 34% ± 12% and 20% ± 10% (p < 0.05) at 60 min. Results suggest phenolics might be a factor modulating glycemic response of oat products.