Measurement of plasma procyanidin B-2 and procyanidin B-3 levels after oral administration in rat

Relationship between hemodynamic alteration and sympathetic nerve activation following a single oral dose of cinnamtannin A2

We previously found that a single dose of B-type procyanidin mixture increase in skeletal muscle blood flow (BF). We compared BF changes following administration of (-)-epicatechin (EC, monomer) and the B-type procyanidins procyanidin B2 (B2, dimer), procyanidin C1 (C1, trimer), and cinnamtannin A2 (A2, tetramer). Each chemical was administered orally to rats, followed by BF measurement in cremaster arteriole for 60 min. About 10 and 100 µg/kg of B2 and C1 elicited BF increase, the effect was potent at 100 µg/kg. BF also increased significantly after administration of 10 µg/kg A2, but not with the administration at 100 µg/kg. EC yielded no BF changes. Co-treatment with the nonselective adrenaline blocker carvedilol attenuated the BF increase seen with 10 µg/kg A2 treatment. This outcome suggested the involvement of sympathetic nerve activation in the BF increase by this dose of A2. Co-treatment of 100 µg/kg A2 with the α2 blocker yohimbine exhibited an increase of BF significantly. The α2 adrenaline receptor in the vasomotor centre is an inhibitory receptor and it regulates hemodynamics. This result suggested that high doses of A2 did not alter BF because of activating the α2 adrenergic receptor. Phosphorylation of aortic endothelial nitric oxide synthase (eNOS) increased with 10 µg/kg A2 alone or co-treatment with 100 µg/kg A2 and yohimbine, but not with co-treatment of 10 µg/kg A2 and carvedilol or 100 µg/kg A2 alone. These results imply that A2 does not directly activate eNOS, but that shear stress from the increased BF might be associated with eNOS phosphorylation.

Onset of a hypotensive effect following ingestion of flavan 3-ols involved in the activation of adrenergic receptors

A lot of epidemiological and intervention studies support the hypotensive action resulting from ingestion of foods rich in flavan 3-ols. However, the mechanisms of this action remain unclear. We have reported previously on the alteration of the micro- and systemic circulations after administration of a flavan 3-ol fraction (FL) derived from cocoa in mammals. We also confirmed that blood catecholamine levels increase significantly after administration of FL. In the present study, we examined whether adrenaline receptors are involved in the hemodynamic changes using several adrenaline receptor (AR) blockers. First, we confirmed that mean blood pressure (MBP) decreased significantly and aortic endothelial nitric oxide synthase (eNOS) levels increased significantly following oral treatment of 10mg/kg FL for 2 weeks in normal rats compared with vehicle administration. However, these changes were not observed with treatment of 1mg/kg (-)-epicatechin (EC), which contains nearly equivalent amount of 10mg/kg FL. Secondly, we observed that a single dose of FL produced different hemodynamic changes, such as a transient elevation in heart rate (HR) after ingestion of 1-100mg/kg FL, but not with 1mg/kg EC. Furthermore, although MBP rose transiently after 1 and 10mg/kg FL, this effect was not observed with 100mg/kg or 1mg/kg EC. The increases in HR, MBP, and aortic phosphorylated eNOS (p-eNOS) induced by 10mg/kg FL were prevented completely by pretreatment with the AR blocker, carvedilol. Combination treatment with 100mg/kg FL and an α1AR blocker, prazosin, significantly reduced MBP, whereas the elevation in HR was enhanced. In addition, after pretreatment with the β2AR blocker, butoxamine, we observed no significant hemodynamic changes with or without 100mg/kg FL. Moreover, the combination of 100mg/kg FL and the α2AR blocker, yohimbine, markedly increased MBP, HR and aortic p-eNOS level. These results suggested that the postprandial hemodynamic changes after a single oral dose of FL were induced by an adrenergic effect. This adrenomimetic activity suggested the involvement of a hypotensive effect of FL.

Differential modulation of apoptotic processes by proanthocyanidins as a dietary strategy for delaying chronic pathologies

Apoptosis is a biological process necessary for maintaining cellular homeostasis. Several diseases can result if it is deregulated. For example, inhibition of apoptotic signaling pathways is linked to the survival of pathological cells, which contributes to cancer, whereas excessive apoptosis is linked to neurodegenerative diseases, partially via oxidative stress. The activation or restoration of apoptosis via extrinsic or intrinsic pathways combined with cell signaling pathways triggered by reactive oxygen specises (ROS) formation is considered a key strategy by which bioactive foods can exert their health effects. Proanthocyanidins, a class of flavonoids naturally found in fruits, vegetables, and beverages, have attracted a great deal of attention not only because they are strong antioxidants but also because they appear to exert a different modulation of apoptosis, stimulating apoptosis in damaged cells, thus preventing cancer or reducing apoptosis in healthy cells, and as a result, preserving the integrity of normal cells and protecting against neurodegenerative diseases. Therefore, proanthocyanidins could provide a defense against apoptosis induced by oxidative stress or directly inhibit apoptosis, and they could also provide a promising treatment for a variety of diseases. Emerging data suggest that proanthocyanidins, especially those that humans can be persuaded to consume, may be used to prevent and manage cancer and mental disorders.

Evaluation of the Quality of Chinese and Vietnamese Cassia Using LC-MS and Multivariate Analysis

In the present study, the chemical composition of water extracts of Chinese and Vietnamese cassia (Cinnamomum cassia) were compared using multivariate analysis of LC-MS data. By principal component analysis of the LC-MS data, 6 compounds, cinnzeylanine (1), cinnzeylanol (2), anhydrocinnzeylanol (3), cinncasinol A (4), epicatechin (5) and procyanidin B2 (6), were identified as the marker compounds to characterize Chinese and Vietnamese cassia. It was clarified that Chinese cassia contains relatively larger amounts of epicatechin and procyanidin B2. On the other hand, Vietnamese cassia is characterized by a relatively larger amount of diterpenes. As catechin derivatives and diterpenes have different types of activity, it is important to choose the cassia that best suits the product for which it is to be used, whether in food or in herbal medicine.

High molecular weight persimmon tannin ameliorates cognition deficits and attenuates oxidative damage in senescent mice induced by D-galactose

Mice were subcutaneously injected with d-galactose (D-gal, 150 mg/kg per day) for 6 weeks and were administered high molecular weight persimmon condensed tannin (HMWPT) simultaneously. After 6 weeks of treatment, the animal behavior was observed in the open field test and water maze test, and the morphology of hippocampus and skin were checked. Meanwhile, the activities of antioxidant enzymes, the levels of non-enzymatic antioxidants, as well as malondialdehyde (MDA) were evaluated. The results indicated that HMWPT markedly inhibited the d-gal induced learning and memory impairment in both open field test and Morris water maze. Biochemical examination revealed that HMWPT significantly increased the decreased activities of superoxide dismutase (SOD), catalase (CAT), elevated the lowered total anti-oxidation capability (T-AOC), glutathione (GSH) and hydroxyproline (Hyp) contents (p<0.01 or p<0.05), and decreased the raised monoamine oxidase (MAO), total cholinesterase (TChE) activities and MDA level (p<0.01) in serum, liver or brain of aging mice induced by d-gal in a dose-dependent fashion. Furthermore, HMWPT significantly and (p<0.01) attenuated the d-gal induced number decrease, neuronal degeneration and karyopycnosis in cells in the hippocampus and decrease of thickness of skin epidermis and dermis.

Proanthocyanidin metabolites associated with dietary fibre from in vitro colonic fermentation and proanthocyanidin metabolites in human plasma

Proanthocyanidins (PAs) or condensed tannins, a major group of dietary polyphenols, are oligomers and polymers of flavan-3-ol and flavan-3, 4-diols widely distributed in plant foods. Most literature data on PAs' metabolic fate deal with PAs that can be extracted from the food matrix by aqueous-organic solvents ( extractable proanthocyanidins). However, there are no data on colonic fermentation of non-extractable proanthocyanidins (NEPAs), which arrive almost intact to the colon, mostly associated to dietary fibre (DF). The aim of the present work was to examine colonic fermentation of NEPAs associated with DF, using a model of in vitro small intestine digestion and colonic fermentation. Two NEPA-rich materials obtained from carob pod (Ceratonia siliqua L. proanthocyanidin) and red grapes (grape antioxidant dietary fibre) were used as test samples. The colonic fermentation of these two products released hydroxyphenylacetic acid, hydroxyphenylvaleric acid and two isomers of hydroxyphenylpropionic acid, detected by HPLC-ESI-MS/MS. Differences between the two products indicate that DF may enhance the yield of metabolites. In addition, the main NEPA metabolite in human plasma was 3,4-dihydroxyphenyl acetic acid. The presence in human plasma of the same metabolites as were detected after in vitro colonic fermentation of NEPAs suggests that dietary NEPAs would undergo colonic fermentation releasing absorbable metabolites with potential healthy effects.

Hypolipidemic effects of proanthocyanidins and their underlying biochemical and molecular mechanisms

Proanthocyanidins are the most abundant polyphenols in human diets. Epidemiological studies strongly suggest that proanthocyanidins protect against cardiovascular diseases. Despite the antioxidant and anti-inflammatory properties of these flavonoids, one of the mechanisms by which proanthocyanidins exert their cardiovascular protection is improving lipid homeostasis. Animal studies demonstrate that proanthocyanidins reduce the plasma levels of atherogenic apolipoprotein B-triglyceride-rich lipoproteins and LDL-cholesterol but increase antiatherogenic HDL-cholesterol. The results in humans, however, are less clear. This review summarizes the results that have been published on plasma triglyceride, apolipoprotein B, HDL-cholesterol and LDL-cholesterol levels in humans and animal models in response to proanthocyanidin extracts and proanthocyanidin-rich foods. The physiological processes and biochemical pathways that are related to lipid homeostasis and affected by proanthocyanidin consumption are also discussed. Intestinal lipid absorption, chylomicron secretion by the intestine and VLDL secretion by the liver are the processes that are most repressed by proanthocyanidins, which, therefore, induce hypolipidemic effects.

Tannins: current knowledge of food sources, intake, bioavailability and biological effects

Tannins are a unique group of phenolic metabolites with molecular weights between 500 and 30 000 Da, which are widely distributed in almost all plant foods and beverages. Proanthocyanidins and hydrolysable tannins are the two major groups of these bioactive compounds, but complex tannins containing structural elements of both groups and specific tannins in marine brown algae have also been described. Most literature data on food tannins refer only to oligomeric compounds that are extracted with aqueous-organic solvents, but a significant number of non-extractable tannins are usually not mentioned in the literature. The biological effects of tannins usually depend on their grade of polymerisation and solubility. Highly polymerised tannins exhibit low bioaccessibility in the small intestine and low fermentability by colonic microflora. This review summarises a new approach to analysis of extractable and non-extractable tannins, major food sources, and effects of storage and processing on tannin content and bioavailability. Biological properties such as antioxidant, antimicrobial and antiviral effects are also described. In addition, the role of tannins in diabetes mellitus has been discussed.

Dose-dependent hypocholesterolemic actions of dietary apple polyphenol in rats fed cholesterol

The dose-dependent hypocholesterolemic and antiatherogenic effects of dietary apple polyphenol (AP) from unripe apple, which contains approximately 85% catechin oligomers (procyanidins), were examined in male Sprague-Dawley rats (4 wk of age) given a purified diet containing 0.5% cholesterol. Dietary AP at 0.5 and 1.0% levels significantly decreased the liver cholesterol level compared with that in the control (AP-free diet-fed) group. Dietary AP also significantly lowered the serum cholesterol level compared with that in the control group. However, the HDL cholesterol level was significantly higher in the 1.0% AP-fed group than in the control group. Accordingly, the ratio of HDL-cholesterol/total cholesterol was significantly higher in the 0.5% AP-fed group and 1.0% AP-fed group than in the control group. Moreover, the atherogenic indices in the 0.5 and 1.0% AP-fed groups were significantly lower than those in the control group. The activity of hepatic cholesterol 7alpha-hydroxylase tended to be increased by dietary AP in a dose-dependent manner. In accord with this observation, dietary AP increased the excretion of acidic steroids in feces. Dietary AP also significantly promoted the fecal excretion of neutral steroids in a dose-dependent manner. These observations suggest that dietary AP at a 0.5 or 1.0% level exerts hypocholesterolemic and antiatherogenic effects through the promotion of cholesterol catabolism and inhibition of intestinal absorption of cholesterol.

Occurrence and biological significance of proanthocyanidins in the American diet

Dietary intake of proanthocyanidins (PAs) has been largely unknown because of the lack of reliable values for their content in foods. Recent development of an analytical method for PAs has allowed the quantification of individual oligomers and polymers. This method has been employed to analyze food samples collected under the USDA National Food and Nutrition Analysis Program. A database of the PA content in common foods and also infant foods has been established. It has been shown that PAs account for a major fraction of flavonoids ingested in the US diet and infants and children appear to ingest more PAs than adults on the basis of body weight. These data will provide an opportunity to examine the association between PA intake and health and disease outcomes in epidemiological studies. PA analysis and the significance of PAs in nutrition and diet are reviewed.

Determination of proanthocyanidins in fresh grapes and grape products using liquid chromatography with mass spectrometric detection

Fresh grapes and grape products, such as grape wine and grape juice, were analyzed for proanthocyanidins (PACs) using liquid chromatography with electrospray ionization mass spectrometric (MS) detection. PACs were successfully separated and analyzed on the basis of their protonated molecules, allowing the identification of PACs in different degrees of polymerization from monomers to oligomers (up to 7 units), and in various isomeric forms. Using reversed-phase high-performance liquid chromatography (HPLC) combined with MS detection, the PAC monomers, (+)-catechin (C), (-)-epicatechin (EC), (-)-catechin gallate (CG), and (-)-epicatechin gallate (ECG), were successfully quantified using selected ion monitoring (SIM) mode. Standard curves were fitted for each PAC ranging from 43.8 to 5600 ng/mL for C, from 42.2 to 5400 ng/mL for EC, from 36.7 to 4700 ng/mL for CG, and from 39.8 to 5100 ng/mL for ECG. Good linearity (r2>0.999) was achieved for each analyte. The accuracy and precision (RSD) were within 10% (n=8) at the limit of detection. This method allows direct quantification of monomeric PACs in fresh grapes and grape-derived products. Additionally, flow injection analysis (FIA) was applied to estimate the concentration levels of PAC oligomers by comparing their FIA-MS peak areas, which were well correlated (r2=0.936) to the total concentrations of PAC monomers.