Stability of anthocyanins in bokbunja (Rubus occidentalis L.) under in vitro gastrointestinal digestion

The stability of anthocyanins in bokbunja (Rubus occidentalis L.) extract was investigated using an in vitro simulated gastrointestinal digestion. Ethanolic extract from bokbunja was digested with pepsin/HCl for 2 h at 37 degrees C, followed by pancreatin/bile salts for 2 h at 37 degrees C. Four anthocyanins including cyanidin-3-glucoside, cyanidin-3-sambubioside, cyanidin-3-xylosylrutinoside and cyanidin-rutinoside were identified in the bokbunja extract. The total anthocyanin content of bokbunja was 3.76 mg cyanidin-3-glucoside equivalents/g fresh weight (FW). Gastric digestion had no significant effect on anthocyanins. However, intestinal digestion substantially decreased anthocyanins up to 1.70 mg/g FW, corresponding to 45% of that in the bokbunja extract. This indicates that about half of anthocyanins can reach an intestinal tract. In addition, a new compound comprised of cyanidin-3-glucosdie, catechin and acetaldehyde in a separated study was observed after in vitro gastrointestinal digestion. This shows that anthocyanins could be transformed into other compounds with different biochemical properties.