Condensed tannins (CTs) have been studied extensively as potential defenses against pests and pathogens, and for their beneficial effects on human health. They are known to possess high in vitro ...antioxidant capacity, but whether they can function as in planta antioxidants for protection against oxidative stress has not been previously tested. Here, we show that stress induction of CTs in poplar (Populus) is matched closely by an increase in antioxidant activity under both high light and nitrogen deficiency. We also investigate the effects of CTs as in vivo antioxidants directly, using transgenic poplar plants which overexpress poplar MYB transcription factors that regulate the CT pathway. These transgenics have 50-fold higher CT concentrations than controls, and and also have dramatically higher antioxidant activity. High-CT and control poplar leaves were exposed to methyl viologen for 24 h. Chlorophyll fluorescence was used to measure maximum quantum efficiency of photosystem II photochemistry (Fv/Fm), and leaf discs were stained with 3,3'-diaminobenzidine (DAB) and nitroblue tetrazolium (NBT) to assess hydrogen peroxide and superoxide levels. After methyl viologen exposure, high-CT transgenics retained higher Fv/Fm ratios and accumulated less hydrogen peroxide and superoxide than the controls. Our findings indicate that high-CT concentrations protect poplar against methyl viologen-induced oxidative stress and suggest a broader function of CTs than previously supposed.
We report to use the main protease (M
) of SARS-Cov-2 to screen plant flavan-3-ols and proanthocyanidins. Twelve compounds, (-)-afzelechin (AF), (-)-epiafzelechin (EAF), (+)-catechin (CA), ...(-)-epicatechin (EC), (+)-gallocatechin (GC), (-)-epigallocatechin (EGC), (+)-catechin-3-O-gallate (CAG), (-)-epicatechin-3-O-gallate (ECG), (-)-gallocatechin-3-O-gallate (GCG), (-)-epigallocatechin-3-O-gallate (EGCG), procyanidin A2 (PA2), and procyanidin B2 (PB2), were selected for docking simulation. The resulting data predicted that all 12 metabolites could bind to M
. The affinity scores of PA2 and PB2 were predicted to be -9.2, followed by ECG, GCG, EGCG, and CAG, -8.3 to -8.7, and then six flavan-3-ol aglycones, -7.0 to -7.7. Docking characterization predicted that these compounds bound to three or four subsites (S1, S1', S2, and S4) in the binding pocket of M
via different spatial ways and various formation of one to four hydrogen bonds.
analysis with 10 available compounds showed that CAG, ECG, GCG, EGCG, and PB2 inhibited the M
activity with an IC
value, 2.98 ± 0.21, 5.21 ± 0.5, 6.38 ± 0.5, 7.51 ± 0.21, and 75.3 ± 1.29 μM, respectively, while CA, EC, EGC, GC, and PA2 did not have inhibitory activities. To further substantiate the inhibitory activities, extracts prepared from green tea (GT), two muscadine grapes (MG), cacao, and dark chocolate (DC), which are rich in CAG, ECG, GAG, EGCG, or/and PB2, were used for inhibitory assay. The resulting data showed that GT, two MG, cacao, and DC extracts inhibited the M
activity with an IC
value, 2.84 ± 0.25, 29.54 ± 0.41, 29.93 ± 0.83, 153.3 ± 47.3, and 256.39 ± 66.3 μg/ml, respectively. These findings indicate that on the one hand, the structural features of flavan-3-ols are closely associated with the affinity scores; on the other hand, the galloylation and oligomeric types of flavan-3-ols are critical in creating the inhibitory activity against the M
activity.
This paper reviews pioneering human studies, their limitations and recent investigations on the absorption, metabolism, distribution and excretion (aka bioavailability) of (–)-epicatechin. Progress ...has been made possible by improvements in mass spectrometric detection when coupled to high performance liquid chromatography and through the increasing availability of authentic reference compounds of in vivo metabolites of (–)-epicatechin. Studies have shown that 2-14C(–)-epicatechin is absorbed in the small intestine with the 12 structural-related (–)-epicatechin metabolites (SREMs), mainly in the form of (–)-epicatechin-3′-O-glucuronide, 3′-O-methyl-(–)-epicatechin-5-sulfate and (–)-epicatechin-3′-sulfate, attaining sub-μmol/L peak plasma concentrations (Cmax) ∼1 h after ingestion. SREMs were excreted in urine over a 24 h period in amounts corresponding to 20% of (–)-epicatechin intake. On reaching the colon the flavan-3-ol undergoes microbiota-mediated conversions yielding the 5C-ring fission metabolites (5C-RFMs) 5-(hydroxyphenyl)-γ-valerolactones and 5-(hydroxyphenyl)–γ-hydroxyvaleric acids which appear in plasma as phase II metabolites with a Cmax of 5.8 h after intake and are excreted in quantities equivalent to 42% of the ingested (–)-epicatechin. Other catabolites excreted in 0–24 h urine in amounts equivalent to 28% of intake included 3-(3′-hydroxyphenyl)hydracrylic acid, hippuric acid and 3′-hydroxyhippuric acid. Overall (–)-epicatechin is highly bioavailable with urinary excretion indicating that 95% is absorbed and passes through the circulatory systems as a diversity of phase II metabolites. Rats produce a very different profile of SREMs than that of humans. These findings demonstrate that ex vivo studies investigating the mechanisms underlying the protective effects of (–)-epicatechin on human health should make use of physiological concentrations human of SREMs and 5C-RFMs, and not the parent (–)-epicatechin, with model systems derived from human cells. In epidemiological studies 5-(4′-hydroxyphenyl)-γ-valerolactone-3′-sulfate and 5-(4′-hydroxyphenyl)-γ-valerolactone-3′-O-glucuronide, the principal 5C-RFMs in both plasma and urine, could serve as key biomarkers of (–)-epicatechin intake.
•MS analysis of fermented cocoa beans showed series of signals at m/z 605 and m/z 893.•Signals at m/z 605 were confirmed to be isomers of ethyl-bridged epicatechin dimers.•The first identification of ...epicatechin-ethyl-procyanidin B2 (m/z 893) was provided.•All were formed in cocoa by condensation of epicatechin, B2, and acetaldehyde.
Two series of compounds showing mass signals at m/z 605 and 893 (negative ionization mode) have been detected in fermented cocoa beans. This study objective is to identify these mass signals and characterize their structure in fermented cocoa samples. Our hypothesis is that these signals may correspond to ethyl-bridged flavan-3-ols resulting from flavan-3-ol condensation with acetaldehyde which is a microbial metabolite. Mass spectrometry was used to compare the retention times and mass fragmentation patterns between a model solution using epicatechin and procyanidin dimer B2, the major flavan-3-ols of cocoa, as precursors and extracts of fermented cocoa. Their identification was confirmed: four isomers of ethyl-linked epicatechin as well as several isomers of epicatechin-ethyl-procyanidin B2, in which B2 was mostly linked through its upper unit, were characterized in cocoa. This study demonstrates the presence of flavan-3-ol acetaldehyde condensation products in fermented cocoa beans and provides the first report of epicatechin-ethyl-procyanidin B2.
The aim of the present study was to establish the profiles of soluble free phenolics (SFPs) and bound phenolics (BPs) in high molecular weight (HMW) melanoidin fractions isolated from raw and roasted ...beans of two Theobroma cacao L. varieties. Samples were prepared using three methods (saline treatment and acidic and alkaline hydrolysis) to obtain different forms of phenolic compounds. A total of fifteen phenolics, including three flavan-3-ols, seven phenolic acids, one phenolic aldehyde, and four N-phenylpropenoyl-L-amino acids (NPAs), were identified using ultra-high-performance liquid chromatography coupled to diode array detection and electrospray ionization high-resolution mass spectrometry (UHPLC-DAD-ESI-HR-MSn). In HMW fractions from both studied cocoa types, the main SFPs were N-caffeoyl-L-Asp and procyanidin B2, whereas the main BPs were catechin, epicatechin, ellagic acid, protocatechualdehyde, and N-caffeoyl-L-Asp. The concentrations of individual BPs were much higher than the content of total SFPs. It was also found that, as compared to alkaline hydrolysis, acid hydrolysis released a significantly higher amount of BPs from HMW melanoidin fractions. A comprehensive quantitative analysis indicated significant variation in the investigated phenolic compounds depending on the cocoa type and roasting conditions. An increase in treatment temperature from 110 to 150 °C led to a decline in SFPs and an increment in BPs. The HMW fractions of unroasted Criollo beans exhibited the highest content of SFPs and the lowest content of BPs. The highest BP concentrations were obtained for both cocoa bean varieties roasted at 150 °C. The present study revealed that HMW melanoidin fractions from cocoa beans of different varieties roasted at higher temperatures are a good source of phenolic compounds that can be released under both acidic and alkaline conditions.
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•A total of 15 phenolics were identified by UHPLC-DAD-MSn in melanoidins of two cocoa types.•The bound phenolics level in the HMW cocoa melanoidins was higher than free forms•The soluble free phenolic of the HMW cocoa samples decreased after roasting.•Roasting causes increase in bound phenolics of all of the HMW cocoa melanoidins.•The changes of both phenolics forms depend on the cocoa type and roasting conditions.
Metabolic engineering and synthetic biology have enabled the use of microbial production platforms for the renewable production of many high-value natural products. Titers and yields, however, are ...often too low to result in commercially viable processes. Microbial co-cultures have the ability to distribute metabolic burden and allow for modular specific optimization in a way that is not possible through traditional monoculture fermentation methods. Here, we present an Escherichia coli co-culture for the efficient production of flavonoids in vivo, resulting in a 970-fold improvement in titer of flavan-3-ols over previously published monoculture production. To accomplish this improvement in titer, factors such as strain compatibility, carbon source, temperature, induction point, and inoculation ratio were initially optimized. The development of an empirical scaled-Gaussian model based on the initial optimization data was then implemented to predict the optimum point for the system. Experimental verification of the model predictions resulted in a 65% improvement in titer, to 40.7±0.1mg/L flavan-3-ols, over the previous optimum. Overall, this study demonstrates the first application of the co-culture production of flavonoids, the most in-depth co-culture optimization to date, and the first application of empirical systems modeling for improvement of titers from a co-culture system.
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•Afzelechin titer of 40.7±0.1mg/L from phenylpropanoic acids.•Empirical computational model guided optimization results in 65% increase in titer.•Demonstrate 970-fold improvement in titer over previous monoculture efforts.
Background: Prospective cohort studies have shown that the consumption of cocoa and tea is associated with lower risk of cardiovascular diseases (CVDs), and cocoa and tea have been shown to improve ...CVD risk factors in randomized controlled trials. Cocoa and tea are major dietary sources of the flavan-3-ol epicatechin.
Objective: We investigated the associations of dietary epicatechin intake with 25-y CVD mortality in elderly Dutch men.
Design: We used data from the Zutphen Elderly Study, which was a prospective cohort study of 774 men aged 65–84 y in 1985. Epicatechin intake was estimated 4 times in 15 y with the use of the crosscheck dietary history method. Time-dependent Cox proportional hazards models were used to investigate repeated measures of epicatechin intake in relation to 25-y CVD mortality.
Results: Mean intake of epicatechin was 15.2 ± 7.7 mg/d, and the major dietary sources were tea (51%), apples (28%), and cocoa (7%). During 25 y of follow-up, 329 men died from CVD, 148 died from coronary heart disease (CHD), and 72 men died from stroke. Risk of CHD mortality was 38% lower in men in the top tertile of epicatechin intake than in men in the bottom tertile of epicatechin intake (HR: 0.62; 95% CI: 0.39, 0.98). Epicatechin intake was also significantly associated with 46% lower risk of CVD mortality in men with prevalent CVD (HR: 0.54; 95% CI: 0.31, 0.96) but not in men who were free of CVD.
Conclusions: We show, for the first time to our knowledge, that epicatechin intake is inversely related to CHD mortality in elderly men and to CVD mortality in prevalent cases of CVD. More studies are needed before conclusions can be drawn.
•Post-fermentation highly decreased the flavonol O-glycosides’ contents.•Inhibitory effects on α-glucosidase and α-amylase were decreased after pile-fermentation.•Metabolomics revealed astringent ...compounds‘ contents were decreased.
Pile-fermentation is the most important process of producing ripened pu-erh tea. To study the chemical changes of tea leaves during pile-fermentation (PF), liquid chromatography coupled with tandem mass spectrometry (LC-MS) was used. Untargeted metabolomics analysis revealed that the first stage of PF is crucial in transforming the original secondary metabolites, whereas the contents of flavan-3-ols and gallic acid were decreased after long-term PF. Targeted metabolomics analysis indicated that the levels of puerins (N-ethyl-2-pyrrolidinone substituted gallocatechin and catechin) were significant increased after the first stage of PF, but after long-term PF the levels of flavonol glycosides, procyanidins and galloylated flavan-3-ols were significantly decreased. Accordingly, long-term PF also decreased the inhibition of α-amylase and α-glucosidase activities of the extracts. As a conclusion, pile-fermentation is an important step of changing the polyphenols and bioactivities of pu-erh tea.
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