Biotransformation and metabolism of three mulberry anthocyanin monomers by rat gut microflora

•Metabolism of three mulberry anthocyanin monomers by gut microflora was investigated.•Characterization of metabolites was performed by HPLC-ESI-MS/MS.•In vitro faecal fermentation generated a wide range of phenolic acids.•A combination of conversion steps for metabolism of anthocyanins was presented.•The differential metabolism of the three ACNs in fresh rat feces was investigated.

Anthocyanins (ACNs) are naturally occurring components of human diet. Evidence has accumulated regarding the positive association of their intake with chronic disease. Because microbiota has been considered as a metabolic organ, the bacterial-dependent metabolisms of three types of ACNs from mulberry fruits (cyanidin-3-glucoside (C3G), cyanidin-3-rutinoside (C3R), delphinidin-3-rutinoside (D3R)) during a simulation of large intestine conditions were investigated. ACNs and metabolites were analysed and characterized by high performance liquid chromatography-electrospray ionization-mass spectrum (HPLC-ESI-MS/MS). C3G disappeared after 6 h of metabolism, while C3R and D3R were no longer detected after 8 h. The metabolism of C3G and C3R mainly resulted in the formation of protocatechuic, vanillic, and p-coumaric acids, as well as 2,4,6-trihydroxybenzaldehyde, while the main metabolites of D3R were gallic acid, syringic acid and 2,4,6-trihydroxybenzaldehyde. This research indicated that the intake of ACNs may result in the appearance of specific metabolites that exert a protective effect in the host physiology.