Search Results (5)

Theaflavins, as key bioactive compounds of black tea, are garnering increasing attention. However, research predominantly focuses on theaflavin monomers derived from the enzymatic oxidation of cis-type catechins. In this study, we identify a unique stereoisomer of theaflavin-3-gallate (TF-3-G), named isoneoTF-3-G, in black tea from Camellia ptilophylla (C. ptilophylla), which is rich in trans-catechins. IsoneoTF-3-G, a characteristic theaflavin of C. ptilophylla black tea, is formed by the oxidation of gallocatechin gallate and catechin. It exhibits a bright orange–red color and shows an [M+H]⁺ ion at m/z 717.1449 in positive electron spray ionization-mass spectrometry. Furthermore, isoneoTF-3-G demonstrates potent inhibitory effects on the proliferation of human colorectal carcinoma HCT116 cells, with a half-inhibitory concentration of 56.32 ± 0.34 μM. This study reveals that the mitochondrial pathway is involved in the apoptosis induction of HCT116 cells by isoneoTF-3-G. Specifically, isoneoTF-3-G leads to increased reactive oxygen species in HCT116 cells, decreased mitochondrial membrane potential, and the consequent release of cytochrome c from the mitochondria to the cytosol, activating caspase-9 and caspase-3, which further promotes the cleavage of poly(ADPribose) polymerase. The results of this study enhance our understanding of the composition and synthesis mechanisms of theaflavins and provide foundational evidence for the further development of isoneoTF-3-G and C. ptilophylla. Full article

The goal of the work was to study changes in the activity of the angiotensin-converting enzyme (ACE) and production of reactive oxygen species (ROS) in the aorta of rats after the intraperitoneal injection of stereoisomers of catechin and gallate. The activity of ACE in the aorta sections was determined by measuring the hydrolysis of hippuryl-l-histidyl-l-leucine. The production of ROS in the aorta sections was estimated from the oxidation of dichlorodihydrofluorescein. The time and dose dependences of the effect of catechin stereoisomers and gallate on ACE activity and ROS production in the aorta were studied. It was shown that (+)-catechin and gallate increased the ACE activity and ROS production, and (−)-catechin and (−)-epicatechin did not influence these parameters. The doses of (+)-catechin and gallate that increased the ACE activity to a half-maximal value (AD₅₀) were 0.04 and 0.03 µg/kg, respectively. Fucoidin, a blocker of leukocyte adhesion to the endothelium, reduced the ACE activity to the control level in the aortas of (+)-catechin-treated rats. Full article

P-glycoprotein (Pgp, ABCB1) is a member of one of the largest families of active transporter proteins called ABC transporters. Thanks to its expression in tissues with barrier functions and its broad substrate spectrum, it is an important determinant of the absorption, metabolism and excretion of many drugs. Pgp and/or some other drug transporting ABC proteins (e.g., ABCG2, MRP1) are overexpressed in nearly all cancers and cancer stem cells by which cancer cells become resistant against many drugs. Thus, Pgp inhibition might be a strategy for fighting against drug-resistant cancer cells. Previous studies have shown that certain polyphenols interact with human Pgp. We tested the effect of 15 polyphenols of sour cherry origin on the basal and verapamil-stimulated ATPase activity of Pgp, calcein-AM and daunorubicin transport as well as on the conformation of Pgp using the conformation sensitive UIC2 mAb. We found that quercetin, quercetin-3-glucoside, narcissoside and ellagic acid inhibited the ATPase activity of Pgp and increased the accumulation of calcein and daunorubicin by Pgp-positive cells. Cyanidin-3O-sophoroside, catechin, naringenin, kuromanin and caffeic acid increased the ATPase activity of Pgp, while they had only a weaker effect on the intracellular accumulation of fluorescent Pgp substrates. Several tested polyphenols including epicatechin, trans-ferulic acid, oenin, malvin and chlorogenic acid were ineffective in all assays applied. Interestingly, catechin and epicatechin behave differently, although they are stereoisomers. We also investigated the effect of quercetin, naringenin and ellagic acid added in combination with verapamil on the transport activity of Pgp. In these experiments, we found that the transport inhibitory effect of the tested polyphenols and verapamil was additive or synergistic. Generally, our data demonstrate diverse interactions of the tested polyphenols with Pgp. Our results also call attention to the potential risks of drug–drug interactions (DDIs) associated with the consumption of dietary polyphenols concurrently with chemotherapy treatment involving Pgp substrate/inhibitor drugs. Full article

A “green” solvent-free industrial process (patent pending) is here described for a grape seed extract (GSE) preparation (Ecovitis™) obtained from selected seeds of Veneto region wineries, in the northeast of Italy, by water and selective tangential flow filtration at different porosity. Since a comprehensive, non-ambiguous characterization of GSE is still a difficult task, we resorted to using an integrated combination of gel permeation chromatography (GPC) and electrospray ionization high resolution mass spectrometry (ESI-HRMS). By calibration of retention time and spectroscopic quantification of catechin as chromophore, we succeeded in quantifying GPC polymers up to traces at n = 30. The MS analysis carried out by the ESI-HRMS method by direct-infusion allows the detection of more than 70 species, at different polymerization and galloylation, up to n = 13. This sensitivity took advantage of the nanoscale shotgun approach, although paying the limit of missed separation of stereoisomers. GPC and MS approaches were remarkably well cross-validated by overlapping results. This simple integrated analytical approach has been used for quality control of the production of Ecovitis™. The emerging feature of Ecovitis™ vs. a popular benchmark in the market, produced by a different technology, is the much lower content of species at low n and the corresponding increase of species at high n. Full article

Flavan-3-ols are claimed to be responsible for the cardioprotective effects of cocoa. Alkalized cocoa powder (ALC), commonly used for many non-confectionary products, including beverages, provides less (+)-catechin, (−)-epicatechin, and procyanidins and more (−)-catechin than nonalkalized cocoa powder (NALC). This may affect the plasma appearance of monomeric flavan-3-ol stereoisomers after consumption of NALC vs. ALC. Within a randomized, crossover trial, 12 healthy nonsmokers ingested a milk-based cocoa beverage providing either NALC or ALC. Blood was collected before and within 6 h postconsumption. (+)-Catechin, (−)-catechin, and epicatechin were analyzed in plasma by HPLC as sum of free and glucuronidated metabolites. Pharmacokinetic parameters were obtained by a one-compartment model with nonlinear regression methods. For epicatechin in plasma, total area under the curve within 6 h postconsumption (AUC_0–6h) and incremental AUC_0–6h were additionally calculated by using the linear trapezoidal method. After consumption of NALC and ALC, (+)-catechin and (−)-catechin were mostly not detectable in plasma, in contrast to epicatechin. For epicatechin, total AUC_0–6h was different between both treatments, but not incremental AUC_0–6h. Most kinetic parameters were similar for both treatments, but they varied strongly between individuals. Thus, epicatechin is the main monomeric flavan-3-ol in plasma after cocoa consumption. Whether NALC should be preferred against ALC due to its higher (−)-epicatechin content remains unclear with regard to the results on incremental AUC_0–6h. Future studies should investigate epicatechin metabolites in plasma for a period up to 24 h in a larger sample size, taking into account genetic polymorphisms in epicatechin metabolism and should consider all metabolites to understand inter-individual differences after cocoa intake. Full article