Effect of in vitro gastrointestinal digestion on the composition and bioactivity of anthocyanins in the fruits of cultivated Lycium ruthenicum Murray

Abstract

The composition of anthocyanins in cultivated Lycium ruthenicum Murray (CLM) before and after in vitro gastrointestinal digestion was determined using an HPLC system coupled with an electrospray ionization-time of flight mass spectrometry. The antioxidant activity and α-glucosidase inhibition of the anthocyanins before and after digestion were also studied. The results showed that most of the anthocyanins in CLM were found in glycosylated form, containing glycoside ligands. After digestion, the glycosylated anthocyanins were transformed to anthocyanidins (without glycol-ligands) which exhibited higher antioxidant activity comparatively. Interestingly, although the inhibitory activity of anthocyanins against α-glucosidase was increased by in vitro gastrointestinal digestion, as suggested by IC50 value, the binding affinity of the anthocyanidins to α-glucosidase remained stable, as demonstrated by fluorescence quenching constant. This suggested that the anthocyanidins might have formed the anthocyanidin-α-glucosidase-substrate tertiary complex. Conclusively, in vitro gastrointestinal digestion may enhance the biological activities of CLM anthocyanins, regarding the antioxidant activity and α-glucosidase inhibition.