Metabolism Of Different DP Of Bayberry Leaves Proanthocyanidins And Their Impact On Microbiota

Proanthocyanidins as the condensed tennins formed by polymerization of catechin,gallocatechin or other monomers were reported to exhibit some bioactivities such as antioxidant,anti-cancer,anti-bacterial and cardioprotective activities.The complex structure and degree of polymerization(DP)leads to the low bioaccessibility of proanthocyanidin.The metabolism of proanthocyanidins monomer is relatively clear,but due to the lack of pure proanthocyanidins polymer,the metabolism of proanthocyanidins polymer has not been clear.Bayberry leaves proanthocyanidins(BLP)has a unique monomer structure of EGCG and also has antioxidant and anti obesity effects.Whether its digestion,absorption and metabolic pathway are the same as catechin structure proanthocyanidins needs further study.To further understand the metabolic pathway of proanthocyanidins during digestion tract,the Bayberry leaves proanthocyanidins produced by our lab were applied to cell model,in-vitro fermentation model and mice model to investigate the metabolic pathway of different DP of proanthocyanidins along with their impact on the microbiota.The main contents of the present research are summarized as follows:(1)Preparation of different DP of BLPThe dimer,trimer,tetramer and pentamer were isolated from BLP.9.85±0.32% of trimer was isolated from BLP which is highest of 4 samples.the purity of 4 samples were over 90%.The antioxidant activity of 4 samples were analized.The higher of DP,the lower of FRAP values.No significant difference was found in DPPH assay during4 samples.The CAA value of pentamer was lowest among 4 samples.It can be inferred that the higher of DP,the lower of antioxidant activity.(2)The change of different DP of BLP during in-vitro digestion and fermentationBLP were stable during in-vitro digestion.During in vitro fermentation,dimer and trimer slightly decreased while tetramer and polymer were stable.Mainly dimer and trimer were ultilized by microbiota probably.Only dimer were able to go through Caco-2 monolayer while others not.(3)The metabolic pathway of different DP of BLP in Caco-2 modelThe metabolites were found in dimer and trimer,while others not.A-ring cleavage product of dimer,4-2,4 butanediol-EGC and 4-1,3 butadiene-EGC,were founded in dimer and trimer metabolites.A-ring cleavage product of trimer,4-2,4 butanediol-EGCEGCG was founded in trimer.Dimer and trimer can be catalyzed by cells while tetramer and pentamer cannot.(4)The metabolic pathway of different DP of BLP in in-vitro fermentation model and their impact on human microbiotaThe products of dimer were similar with cell metabolites.The A-ring cleavage products of dimer were also founded in trimer metabolites.The A-ring cleavage products of trimer were not founded in all samples.microbiota was not able to cleavage the A-ring of terminal unit.Dimer and tetramer were able to significantly increase the relative aboundance of Bacteroides Dorei and dimer is higher than tetramer.Trimer,tetramer and pentamer decreased the relative aboundance of bifidobacterium pseudocatenulatum DSM 20438,which might relate to glycolipid metabolism and immune regulation.Pentamer significantly decreased the relative aboundance of Uncultured Bacterium Lachnospiraceae UCG-010,which is related to attenuate metabolic syndrome;also significantly increase the relative aboundance of Unclassified Streptococcus which is related to colone cancer.(5)The metabolic pathway of different DP of Bayberry leaves proanthocyanidins in mice model and their impact on mice microbiotaThe dimer and trimer A-ring cleavage product were identified in trimer and tetramer through mice model.Tetramer A-ring cleavage product was not found in tetramer samples.These indicate that trimer can be metabolized through A-ring cleanage or degraded into dimer.Tetramer were not metabolized through A-ring cleavage but can be degraded into trimer and dimer.The diversity of microbiota was not influenced by BLP while the relative aboundance did.Dimer significantly increased the relative aboundance of Uncultured Clostridiales Bacterium Lachnospiraceae NK4A136 Group,Uncultured Bacterium Dubosiella and Akkermansia Muciniphila,these are probiotics.Trimer was able to increase the relative aboundance of Uncultured Bacterium Dubosiella and Uncultured Clostridiales Bacterium Lachnospiraceae NK4A136 Group.Tetramer significantly increased the relative aboundance of Uncultured Organism Norank Muribaculaceae,which is related to hyperglycemia.