Effects of In Vitro Digestion on the Content and Biological Activity of Polyphenols from Acacia mearnsii Bark

Metabolic Fate of Orally Ingested Proanthocyanidins through the Digestive Tract

Proanthocyanidins (PACs), which are oligomers or polymers of flavan-3ols with potent antioxidative activity, are well known to exert a variety of beneficial health effects. Nonetheless, their bioaccessibility and bioavailability have been poorly assessed. In this review, we focused on the metabolic fate of PACs through the digestive tract. When oligomeric and polymeric PACs are orally ingested, a large portion of the PACs reach the colon, where a small portion is subjected to microbial degradation to phenolic acids and valerolactones, despite the possibility that slight depolymerization of PACs occurs in the stomach and small intestine. Valerolactones, as microbiota-generated catabolites of PACs, may contribute to some of the health benefits of orally ingested PACs. The remaining portion interacts with gut microbiota, resulting in improved microbial diversity and, thereby, contributing to improved health. For instance, an increased amount of beneficial gut bacteria (e.g., Akkermansia muciniphila and butyrate-producing bacteria) could ameliorate host metabolic functions, and a lowered ratio of Firmicutes/Bacteroidetes at the phylum level could mitigate obesity-related metabolic disorders.

A Narrative Review of Human Clinical Trials on the Impact of Phenolic-Rich Plant Extracts on Prediabetes and Its Subgroups

Phenolic-rich plant extracts have been demonstrated to improve glycemic control in individuals with prediabetes. However, there is increasing evidence that people with prediabetes are not a homogeneous group but exhibit different glycemic profiles leading to the existence of prediabetes subgroups. Prediabetes subgroups have been identified as: isolated impaired fasting glucose (IFG), isolated impaired glucose tolerance (IGT), and combined impaired fasting glucose and glucose intolerance (IFG/IGT). The present review investigates human clinical trials examining the hypoglycemic potential of phenolic-rich plant extracts in prediabetes and prediabetes subgroups. Artemisia princeps Pampanini, soy (Glycine max (L.) Merrill) leaf and Citrus junos Tanaka peel have been demonstrated to improve fasting glycemia and thus may be more useful for individuals with IFG with increasing hepatic insulin resistance. In contrast, white mulberry (Morus alba Linn.) leaf, persimmon (Diospyros kaki) leaf and Acacia. Mearnsii bark were shown to improve postprandial glycemia and hence may be preferably beneficial for individuals with IGT with increasing muscle insulin resistance. Elaeis guineensis leaf was observed to improve both fasting and postprandial glycemic measures depending on the dose. Current evidence remains scarce regarding the impact of the plant extracts on glycemic control in prediabetes subgroups and therefore warrants further study.

Effect of drying methods on the gastrointestinal fate and bioactivity of phytochemicals from cocoa pod husk: In vitro and in silico approaches

Cocoa pod husk (CPH) contains many nutraceutical phytochemicals whose gastrointestinal fate and bioactivity can be affected by drying methods. Microwave (MW), forced-air drying (AF), and AF plus extrusion (AF-E) dried CPH samples were chemically characterized, and their phenolic and theobromine (THB) contents were evaluated under oral-gastric-intestinal (in vitro) and colonic fermentation (ex vivo). Absorption, distribution, metabolism, excretion, and toxicity (ADEMT) properties of CPH's small molecules were evaluated in silico. The chemical composition of CPH [mostly carbohydrates/insoluble dietary fiber], polyphenol [total polyphenols > condensed tannin (CT) > monomeric flavonoids] differed minimally among samples, except for THB content (AF/AF-E > MW) and antioxidant capacity (MW > AF/AF-E). Time- trend gastrointestinal (X³ behavior) and colonic bioaccessibility were AF/AF-E > MW, but phenolic acids, procyanidins, and THB fluctuated in a sample-specific fashion. In silico modeling showed that bioactives of CPH easily crossed the intestinal epithelium illustrating their bioaccessibility and, permeability. These bioactives can act as receptor ligands in a structure-dependent manner, suggesting their use as a functional ingredient.

Mainly Dimers and Trimers of Chinese Bayberry Leaves Proanthocyanidins (BLPs) are Utilized by Gut Microbiota: In Vitro Digestion and Fermentation Coupled with Caco-2 Transportation

Chinese bayberry leaf proanthocyanidins (BLPs) are Epigallocatechin gallate (EGCG) oligomers or polymers, which have a lot of health-promoting activity. The activity is closely related to their behavior during in vitro digestion, which remains unknown and hinders further investigations. To clarify the changes of BLPs during gastrointestinal digestion, further research is required. For in vitro digestion, including gastric-intestinal digestion, colon fermentation was applied. Caco-2 monolayer transportation was also applied to investigate the behavior of different BLPs with different degrees of polymerization. The trimers and the tetramers were significantly decreased during in vitro gastric-intestinal digestion resulting in a significant increase in the content of dimers. The dimers and trimers were the main compounds utilized by gut microbiota and they were assumed not to degrade through cleavage of the inflavan bond. The monomers and dimers were able to transport through the Caco-2 monolayer at a rate of 10.45% and 6.4%, respectively.

Characterization and Potential Antidiabetic Activity of Proanthocyanidins from the Barks of Acacia mangium and Larix gmelinii

Proanthocyanidins in ethanol extracts from the barks of Acacia mangium and Larix gmelinii were analyzed by gel permeation chromatography, MALDI-TOF/TOF MS, and HPLC/MS. The inhibitory effects of proanthocyanidins and acid-catalyzed hydrolysis of proanthocyanidins against carbolytic enzymes were also tested. A significant relationship between carbolytic enzymes inhibition and degree of polymerization was established, showing that the degree of polymerization is a major contributor to the biological activity of the proanthocyanidins from both types of woody plant bark. The results indicate that proanthocyanidins from the barks of A. mangium and L. gmelinii have potential antidiabetic properties.

Analytical Profiling of Proanthocyanidins from Acacia mearnsii Bark and In Vitro Assessment of Antioxidant and Antidiabetic Potential

The proanthocyanidins from ethanol extracts (80%, v/v) of Acacia mearnsii (A. mearnsii) bark on chemical-based and cellular antioxidant activity assays as well as carbolytic enzyme inhibitory activities were studied. About 77% of oligomeric proanthocyanidins in ethanol extracts of A. mearnsii bark were found by using normal-phase HPLC. In addition, HPLC-ESI-TOF/MS and MALDI-TOF/TOF MS analyses indicated that proanthocyanidins from A. mearnsii bark exhibited with a degree of polymerization ranging from 1 to 11. These results of combined antioxidant activity assays, as well as carbolytic enzyme inhibitory activities of proanthocyanidins from A. mearnsii bark, indicated an encouraging antioxidant capacity for the high polyphenol content and a potential for use as alternative drugs for lowering the glycemic response.