This study investigated the protective role of lotus seedpod oligomeric procyanidins (LSOPC) and synbiotics (Bifidobacterium Bb-12 and xylo-oligosaccharide) against high fat and streptozotocin (STZ)-induced diabetes. Administration of LSOPC or synbiotics had no effect on blood glucose in normal mice. Treatments with LSOPC for 12 weeks markedly reduced blood glucose, FFA, endotoxin, and GHbA1c and improved glucose homeostasis, lipid metabolism, and insulin levels. In addition, administration of LSOPC significantly reversed the increase of mTOR and p66Shc in liver, skeletal muscle, and white adipose tissue (WAT). LSOPC significantly increased glucose uptake and glycolysis in liver, skeletal muscle, and WAT while improving heat generation in brown adipose tissue (BAT) and inhibiting gluconeogenesis and lipogenesis in liver. Furthermore, synbiotics strengthened the improving effect of LSOPC. These findings demonstrated that LSOPC and synbiotics may regulate glucose disposal in peripheral target tissues through the p66Shc-mTOR signaling pathway.Keywords: glucose homeostasis; lotus seed oligomeric procyanidins; mTOR; synbiotics; type 2 diabetes;

This study investigated the protective properties of lotus seedpod oligomeric procyanidins (LSOPC) against nonalcoholic fatty liver disease (NAFLD) and its underlying mechanism. Sprague–Dawley (SD) male rats were fed a basic diet, a high-fat diet (HFD), or HFD plus 0.2 or 0.5% (w/w) LSOPC for 12 weeks. Administration of LSOPC markedly reduced serum and hepatic biochemical parameters and protein expression of advanced glycation endproducts (AGEs). Additionally, 0.5% (w/w) LSOPC treatment remarkably reversed the increasing tendency of receptor of advanced glycation endproduct (RAGE) to normal level. Furthermore, dietary LSOPC significantly decreased the protein levels of mitogen-activated protein kinases (MAPK) and nuclear factor-kappa B (NF-κB) and down-regulated genes involved in pro-inflammatory cytokines and adhesion molecules. Taken together, these findings demonstrate that LSOPC may protect obese rats with long-term HFD-induced NAFLD against RAGE-MAPK-NF-κB signaling suppression.

It has been reported that oligomeric procyanidins of lotus seedpod (LSOPC) is effective in the alleviation of Alzheimer’s disease and diabetes through its antioxidant and insulin-potentiating activities. This study investigated the anti-glycative activity of LSOPC in a bovine serum albumin (BSA)-glucose model. The level of glycation and conformational alterations were assessed by specific fluorescence, Congo red binding assay and circular dichroism. The results show that LSOPC has a significant anti-glycative activity in vitro and it can also effectively protect the secondary structure of BSA during glycation. LSOPC or catechin (a major constituent unit of LSOPC), were used to react with methylglyoxal. The structures of their carbonyl adducts were tentatively identified using HPLC-MS2. Their capacity to scavenge methylglyoxal suggested carbonyl scavenging as a major mechanism of antiglycation. Therefore, LSOPC could be helpful to prevent AGEs-associated diseases, and with the potential to be used as functional food ingredients.Highlights► LSOPC inhibition rate is significantly higher than that of AG and can protect the structure of BSA effectively in the glycation process. ► The decreased amounts of MGO in LSOPC and catechin are higher than AG. ► The catechin-methylglyoxal adducts and LSOPC-methylglyoxal adducts were identified by LC-MS2.

Intervention studies with A-type oligomeric procyanidins from litchi (Litchi chinensis) pericarp (LPOPC) suggested its protective effect against cardiovascular diseases. However, there is no consensus on the absorption and metabolism of LPOPC. It was demonstrated that the main components in LPOPC were (−)-epicatechin, A-type procyanidin dimers, trimers and tetramers. Rats were orally administered different levels of LPOPC (150 and 300 mg/kg bw), the procyanidins and their microbial metabolites in urine were identified by HPLC–MS/MS analysis 18 h post-administration. Data indicated that seven aromatic acid metabolites excreted were significantly increased by 300 mg/kg bw of LPOPC (P < 0.01). However, only (−)-epicatechin and its methylated derivatives were detected in rat plasma 1 h after 300 mg/kg bw of LPOPC administration. The total EC content absorbed in plasma was only 2.54 ± 0.53 μmol/L, indicating that the biological properties of LPOPC should be probably explained by its microbial degraded phenolic acids.Highlights► The absorption and urinary excretion of A-type procyanidins from monomer to tetramer were investigated in rats. ► The dose–response relationship of the procyanidin intake and its metabolites excreted was discussed. ► The beneficial health effects of A-type procyanidin were in connection with its microbial metabolites.

Litchi chinensis pericarp from litchi processing waste is an important plant source of A-type procyanidins, which were considered a natural dietary supplement because of their high biological activity in vivo. Litchi pericarp oligomeric procyanidins (LPOPCs) did not selectively modify the growth of Streptococcus thermophilus and Lactobacillus casei-01 at concentrations of 0.25 and 0.5 mg/mL, and it was demonstrated that the two strains could transform procyanidins during their log period of growth by two different pathways. S. thermophilus was able to metabolize procyanidin A2 to its isomer, and L. casei could decompose flavan-3-ols into 3,4-hydroxyphenylacetic acid, 4-hydroxyphenylpropionic acid, m-coumaric acid, and p-coumaric acid. The total antioxidant capability (T-AOC) of LPOPCs before and after microbial incubation was estimated, and the results suggested that probiotic bacteria bioconversion is a feasible and efficient method to convert litchi pericarp procyanidins to a more effective antioxidant agent.

Procyanidin oligomers from litchi pericarp (Litchi chinensis) were isolated and identified by online analysis. Accurate molecular weight (MW) distribution and composition of the procyanidin extracts were recorded on an Apex-Qe–FT–ICR mass spectrometer. The MW range of litchi procyanidins was from 289.07151 to 1439.30529 m/z and composed of A- and B-series oligomeric procyanidins. The variety of the main procyanidins (DP < 5) was identified by HPLC and LC–ESI-MS analysis. There are more than 41.7% of A-series procyanidins in the oligomeric procyanidins, however, B-series procyanidins takes only 24.1% of the litchi pericarp extracts. In this study, we determined the effects of (−)-epicatechin, A-type procyanidin dimer (A2) and trimer, epicatechin-(4β→8, 2β→O→7)-epicatechin-(4β→8)-epicatechin from litchi pericarp on free radical scavenging. The results showed that A-type procyanidin dimer and trimer both had a strong scavenging ability on DPPH and OH, indicating that litchi is a new plant source of A-type procyanidins and natural antioxidant.Highlights► Procyanidin oligomers from litchi pericarp were recorded on ultra-high resolution mass spectrometry (Apex-Qe-FT–ICR–MS). ► The main oligomeric procyanidins (DP < 5) in litchi pericarp were identified by HPLC and LC–MS2 analysis. ► The effects of procyanidin oligomers from litchi pericarp on free radical scavenging were determined.