1、Introduction
— Proanthocyanidins (PA) is a kind of natural polyphenols ,which is
widespread in plant and rich in human diet, such as fruits, vegetables, beverages, beans et al. It's an important secondary metabolites of plant , having the efficacy of scavenging free radical , anti-oxidation, anticardiovascular disease,which has become a research hotspot in recent years.
Procyanidin B4
Procyanidin C1
Fig.4 Changes in monomeric, dimeric and trimeric procyanidins flavan-3-ols during faecal fermentation of the grape seed extract
propionic acid derivatives
lacetic acid derivatives
benzoic acid derivatives
Fig3 Metabolic pathway 0f phenolic acids
4.1 Precusor substance
(-)-Epicatechin-3-O-gallate
Changes in the flavan-3-ol profile originally present in the grape seed extract refer to flavan-3-ols:monomers:(+)-catechin, (-)-epicatechin and (-)-epigallocatechin gallate ;dimeric procyanidins :B1, B2, B3, B4,B2-3O-gallate and B2-3'-O-gallate ;trimeric procyanidins :C1and T2.
— General structure of procyanidins in natural substances is complex.
They are mostly in the form of a polymer and hard to be directly absorbed by the gut, which greatly reduces the biological activity of proanthocyanidins .Studying the metabolic processes of procyanidins in vivo , in particular microbial metabolic processes is of great meaning to understandits physiological function .
proanthocyanidin
Monomer
5-(3’,4’-dihydroxyphenyl) -γ-valerolactone
4-hydroxy-5-(3’,4’-dihydroxy phenyl)-valeric acid α，β-oxidation， dehydroxylation reaction
(a) incubations lacking the PAS extract (b) incubations of the PAS extract in medium without faecal microbiota
Methods:
Batch cultures were run under anaerobic conditions for a period of 48 h, collected at six time points (0, 5, 10, 24, 30, and 48 h) in sterile Eppendorf tubes (1.5 ml) and stored at -70℃ until required for the analysis of phenolic compounds by UPLCPAD-ESI-TQ MS.
3.2.4 Other factors
molecular weight, solubility, lipophilicity
4、Microbial catabolism
Living microflora
heat-inactivated microflora
varied substances detected during the microbile in vitro fermentation process. M2 , M3 : mHPP,mHPV; M4: nonhydroxylated aromatic acids
3.2.1 DP
Monomeric flavan-3-ols are readily absorbed in the small intestine; dimeric procyanidins present low absorption, whereas oligomeric and polymeric forms require activities by the colonic microbiota in order to be absorbed and further metabolised.
C4-C8 bond
monomeric units of PAs
3、Absorption
3.1 Routes for dietary polyphenols
Fig. 1 Routes for dietary polyphenols and their metabolites in humans.
3.2 Factors affecting absorption
Fig.2 Proanthocyanidin polymers incubated with human colonic microflora over varioustime periods.
In Vitro Fermentation experiment
Batch-culture fermentations:
B4 B2-3-O-gallate B2-3'-O-gallate
C1 T2
15.0 ± 0.13 1.80 ± 0.06 1.61 ± 0.01
7.07 ± 0.08 6.81 ± 0.06
2、Structure
Flavan-3-ols occur as monomeric, oligomeric, or polymeric forms, and the latter two are also known as proanthocyanidins or condensed tannins. Main flavanol monomeric units include catechin, epicatechin, and epicatechin-3-Ogallate. Proanthocyanidins are constituted of flavanol units linked by C4−C6 or C4−C8 bonds.
R5 R4 R3 R2 O R1
+
R5 7
A
R7 R3 R2
It is suggested that undergo a ring-fission and degraded ; hydroxylated aromatic compounds are formed from the A-ring and phenolic acids from the B-ring.
Absorption and gut microbial catabolism of PAs
小组成员：贤 欢 文 雅 尧 咏 叶蕾蕾 2013309110037 2013309110036 2013309110038 2013309110039
Content
1
2 3 4 5
Introduction Structure Absorption in vivo Microbial catabolism Summarize
3.2.3 Gut microbile
The number of bacterial cells and species present varies in the mammalian gut. A continuum goes from 101 to 103 bacteria/gram of contents in the stomach and duodenum, progressing to 104 to 107 bacteria/gram in the jejunum and ileum and culminating in 1011 to 1012 cells per gram inthe colon. Samples from the small intestine are rich in the Bacilli class of Firmicutes and Actinobacteria, whereas Bacteroidetes and the Lachnospiraceae family of the Firmicutes aremore prevalent in the colon.
Vessels were inoculated with 15 ml of faecal slurry (1:10,w/v) and then Vitaflavan grape seed extract was addedat a final concentration of 600 mg/l.