Metabolism of anthocyanins and their phenolic degradation products by the intestinal microflora.

Anthocyanins are suggested to be responsible for protective effects against cardiovascular diseases and certain forms of cancer. Although previous studies have implicated that intact anthocyanidin glycosides were decreased extensively by interactions in the gastrointestinal tract, only few data are available concerning the metabolism by the intestinal microflora. Using a new in vitro model, we have investigated the microbial deglycosylation and degradation of six anthocyanins exhibiting three different aglycones with mono- or di-beta-D-glycosidic bonds using high-performance liquid chromatography-diode array (HPLC-DAD) and gas chromatography-mass spectrometry (GC-MS) detection. We have found that all anthocyanidin glycosides were hydrolysed by the microflora within 20 min and 2 h of incubation depending on the sugar moiety. Due to the high instability of the liberated aglycones at neutral pH, primary phenolic degradation products were already detected after 20 min of incubation. Further metabolism of the phenolic acids was accompanied by demethylation. Because of their higher chemical and microbial stability, phenolic acids and/or other, not yet identified, anthocyanin metabolites might be mainly responsible for the observed antioxidant activities and other physiological effects in vivo.