Extraction Methods, Properties, Functions, and Interactions with Other Nutrients of Lotus Procyanidins: A Review.

Lotus procyanidins, natural polyphenolic compounds isolated from the lotus plant family, are widely recognized as potent antioxidants that scavenge free radicals in the human body and exhibit various pharmacological effects, such as anti-inflammatory, anticancer, antiobesity, and hypoglycemic. With promising applications in food and healthcare, lotus procyanidins have attracted extensive attention in recent years. This review provides a comprehensive summary of current research on lotus procyanidins, including extraction methods, properties, functions, and interactions with other nutrient components. Furthermore, this review offers an outlook on future research directions, providing ideas and references for the exploitation and utilization of lotus.

Molecular Mechanism of Lotus Seedpod Oligomeric Procyanidins Inhibiting the Absorption of Oligopeptide-Advanced Glycation End Products.

Research on advanced glycation end product (AGEs) inhibition has generally focused on food processing, but many protein-AGEs will still be taken. Oligopeptide (OLP)-AGEs, as the main form after digestion, will damage human health once absorbed. Here, we investigated the ability of lotus seedpod oligomeric procyanidins (LSOPC) to inhibit the absorption of the OLP-AGEs and elucidated the underlying mechanism. Our results showed that the inhibition rate of LSOPC on the absorption of OLP-AGEs was about 50 ± 5.38%. 0.1, 0.2, and 0.3 mg/mL could upregulate the expression of ZO-1 and downregulate the expression of PepT1 and clathrin. Molecular docking showed that LSOPC could compete with the binding of OLP-AGEs to PepT1 and AP-2, thus inhibiting the absorption of OLP-AGEs. Furthermore, the interaction of LSOPC with the OLP-AGEs reduced the surface hydrophobicity of OLP-AGEs. It altered the secondary structure of the OLP-AGEs, thus weakening the affinity of the OLP-AGEs to the transporter protein to inhibit the absorption of OLP-AGEs. Together, our data revealed potential mechanisms by which LSOPC inhibit the absorption of OLP-AGEs and opened up new perspectives on the application of LSOPC in reducing the increasing health risks posed by OLP-AGEs.

Structure relationship of non-covalent interactions between lotus seedpod oligomeric procyanidins and glycated casein hydrolysate during digestion.

Procyanidin-amino acid interactions during transmembrane transport cause changes in the structural and physical properties of peptides, which limits further absorption of oligopeptide-advanced glycation end products (AGEs). In this study, glycated casein hydrolysates (GCSHs) were employed to investigate the structure and interaction mechanism of GCSH with lotus seedpod oligomeric procyanidin (LSOPC) complexes in an intestinal environment. LSOPC can interact with GCSH under certain conditions to form hydrogen bonds and hydrophobic interactions to form GCSH-LSOPC complexes. Results showed that procyanidin further leads to the transformation of a GCSH secondary structure and the increase of surface hydrophobicity (H0). The strongest non-covalent interaction between GCSH and (-)-epigallocatechin gallate (EGCG) was due to the polyhydroxy structure of EGCG. Binding site analysis showed that EGCG binds to the internal cavity of P1 to maintain the relative stability of the binding conformation. The antioxidant capacity of GCSH was remarkably elevated by GCSH-LSOPC. This study will provide a new reference for the accurate control of oligopeptide-AGEs absorption by LSOPC in vivo.

Protective mechanism of fruit vinegar polyphenols against AGEs-induced Caco-2 cell damage.

Accumulation of advanced glycation end products (AGEs) is linked with development or aggravation of many degenerative processes or disorders. Fruit vinegars are rich in polyphenols that can be a good dietary source of AGEs inhibitors. In this study, eight kinds of vinegars were prepared. Among them, the highest polyphenol and flavonoid content were orange vinegar and kiwi fruit vinegar, respectively. Ferulic acid, vanillic acid, chlorogenic acid, p-coumaric acid, caffeic acid, catechin, and epicatechin were main polyphenols in eight fruit vinegars. Then, we measured the inhibitory effect of eight fruit vinegars on fluorescent AGEs, and found that orange vinegar had the highest inhibitory rate. Data here suggested that orange vinegar and its main components catechin, epicatechin, and p-coumaric acid could effectively reduce the level of ROS, RAGE, NADPH and inflammatory factors in Caco-2 cells. Our research provided theoretical basis for the application of orange vinegar as AGEs inhibitor.

Role of glycated proteins in vivo: Enzymatic glycated proteins and non-enzymatic glycated proteins.

Glycated protein is a kind of substance that often exists in the human body through the combination of sugar and protein under enzyme or non-enzyme conditions. Enzyme-catalyzed glycated proteins are widely distributed in the human body and participate in life activities such as human growth and immune regulation. Non-enzymatic glycated protein is often related to cancer, aging, diabetes and other diseases, but in vitro non-enzymatic glycated protein has utility value after modification. This review not only discussed the effects of enzymatic glycated protein on human intestinal health, immune regulation and cancer prevention. The inhibition methods of non-enzymatic glycated protein in food processing, digestion, absorption and metabolism were also elucidated.

Comparative study of the inhibitory effects of lotus seedpod oligomeric procyanidins on dietary AGE released from glycated casein during digestion.

Glycation of protein results in the formation of advanced glycation end-products (AGEs), which are further absorbed by the body through digestion in the gastrointestinal tract. The inhibitory properties of procyanidin for the release of AGEs from glycated proteins are of great significance in promoting, accelerating or stabilizing gastrointestinal folding intermediates, although the mechanism of action remains unclear. With the background of dairy processing, the study investigated the inhibitory effect of lotus seedpod oligomeric procyanidins (LSOPC) and its three monomers on AGE release from glycated casein (G-CS) during gastrointestinal digestion. In gastrointestinal microenvironments, multispectral and microscopy analysis were used to investigate interaction mechanisms. Results showed that the binding force of the protein-procyanidin complexes were hydrogen bonding and hydrophobic interaction and LSOPC leaded the G-CS secondary structure transformations furtherly. In the gastric environment, all monomers displayed stronger binding to pepsin but in the intestinal environment, results were opposite. Molecular docking showed that procyanidins were bound in the internal cavity of G-CS, pepsin and pancreatin, thereby forming a relatively stable binding conformation. Moreover, procyanidins enhanced the antioxidant capacity of G-CS, which could attenuate postprandial oxidative stress in the gastrointestinal tract caused by the release of AGEs. Together, this study improves our understanding of dietary AGEs during gastrointestinal digestion.

Inhibition of advanced glycation endproducts formation by lotus seedpod oligomeric procyanidins through RAGE-MAPK signaling and NF-κB activation in high-AGEs-diet mice.

This study investigated the modulatory effects of lotus seedpod oligomeric procyanidins (LSOPC) on the advanced glycation endproducts (AGEs)-induced liver injury via advanced glycation end-product receptors (RAGE)-mitogen-activated protein kinases (MAPK)-nuclear factor-kappa B (NF-κB) signaling pathways in a mice model. To examine the antioxidation properties of LSOPC, a model of high-AGEs-diet were established using Sprague Dawley (SD) male mice fed with a normal AIN-93G diet, a high AGEs diet (H), or H plus 0.5 or 0.2% (w/w) LSOPC for 12 weeks. Our results showed that LSOPC inhibited the AGEs formation and alleviated AGEs-induced liver injury by suppressing the nuclear translocation of NF-κB and activation of the MAPK signaling pathway. Additionally, LSOPC inhibited the genes expression of tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6). Taken together, LSOPC treatment potentially inhibited the AGEs formation and modulated liver injury with long-term dietary AGEs by suppressing RAGE-MAPK-NF-κB pathways.