Gerard Bryan Gonzales

Angiotensin-Converting Enzyme Inhibitory Effects by Plant Phenolic Compounds: A Study of Structure Activity Relationships

In this study, 22 phenolic compounds were investigated to inhibit the angiotensin-converting enzyme (ACE). Tannic acid showed the highest activity (IC50 = 230 μM). The IC50 values obtained for phenolic acids and flavonoids ranged between 0.41 and 9.3 mM. QSAR analysis confirmed that the numbers of hydroxyl groups on the benzene ring play an important role for activity of phenolic compounds and that substitution of hydroxyl groups by methoxy groups decreased activity. Docking studies indicated that phenolic acids and flavonoids inhibit ACE via interaction with the zinc ion and this interaction is stabilized by other interactions with amino acids in the active site. Other compounds, such as resveratrol and pyrogallol, may inhibit ACE via interactions with amino acids at the active site, thereby blocking the catalytic activity of ACE. These structure-function relationships are useful for designing new ACE inhibitors and potential blood-pressure-lowering compounds based on phenolic compounds.

Ultra(high)-pressure liquid chromatography-electrospray ionization-time-of-flight-ion mobility-high definition mass spectrometry for the rapid identification and structural characterization of flavonoid glycosides from cauliflower waste.

In this paper, a strategy for the detection and structural elucidation of flavonoid glycosides from a complex matrix in a single chromatographic run using U(H)PLC-ESI-IMS-HDMS/MS(E) is presented. This system operates using alternative low and high energy voltages that is able to perform the task of conventional MS/MS in a data-independent way without re-injection of the sample, which saves analytical time. Also, ion mobility separation (IMS) was employed as an additional separation technique for compounds that are co-eluting after U(H)PLC separation. First, the fragmentation of flavonoid standards were analyzed and criteria was set for structural elucidation of flavonoids in a plant extract. Based on retention times, UV spectra, exact mass, and MS fragment characteristics, such as abundances of daughter ions and the presence of radical ions ([Y0-H](-)), a total 19 flavonoid glycosides, of which 8 non-acylated and 11 acylated, were detected and structurally characterized in a cauliflower waste extract. Kaempferol and quercetin were the main aglycones detected while sinapic and ferulic acid were the main phenolic acids. C-glycosides were also found although their structure could not be elucidated. The proposed method can be used as a rapid screening test for flavonoid identification and for routine analysis of plant extracts, such as these derived from cauliflower waste. The study also confirms that agroindustrial wastes, such as cauliflower leaves, could be seen as a valuable source of different bioactive phenolic compounds.

Flavonoid interactions during digestion, absorption, distribution and metabolism: a sequential structure–activity/property relationship-based approach in the study of bioavailability and bioactivity

Abstract Flavonoids are a group of polyphenols that provide health-promoting benefits upon consumption. However, poor bioavailability has been a major hurdle in their use as drugs or nutraceuticals. Low bioavailability has been associated with flavonoid interactions at various stages of the digestion, absorption and distribution process, which is strongly affected by their molecular structure. In this review, we use structure–activity/property relationship to discuss various flavonoid interactions with food matrices, digestive enzymes, intestinal transporters and blood proteins. This approach reveals specific bioactive properties of flavonoids in the gastrointestinal tract as well as various barriers for their bioavailability. In the last part of this review, we use these insights to determine the effect of different structural characteristics on the overall bioavailability of flavonoids. Such information is crucial when flavonoid or flavonoid derivatives are used as active ingredients in foods or drugs.

Combined Alkaline Hydrolysis and Ultrasound-Assisted Extraction for the Release of Nonextractable Phenolics from Cauliflower (Brassica oleracea var. botrytis) Waste

Cauliflower waste contains high amounts phenolic compounds, but conventional solvent extraction misses high amounts of nonextractable phenolics (NEP), which may contribute more to the valorization of these waste streams. In this study, the NEP content and composition of cauliflower waste were investigated. The ability of alkaline hydrolysis, sonication, and their combination to release NEP was assessed. Alkaline hydrolysis with sonication was found to extract the highest NEP content (7.3 ± 0.17 mg gallic acid equivalents (GAE)/g dry waste), which was higher than the extractable fraction. The highest yield was obtained after treatment of 2 M NaOH at 60 °C for 30 min of sonication. Quantification and identification were done using U(H)PLC-DAD and U(H)PLC-ESI-MS(E). Kaempferol and quercetin glucosides along with several phenolic acids were found. The results of the study show that there are higher amounts of valuable health-promoting compounds from cauliflower waste than what is currently described in the literature.

Bioaccessibility of Polyphenols from Plant-Processing Byproducts of Black Carrot (Daucus carota L.).

Plant-processing byproducts of black carrot represent an important disposal problem for the industry; however, they are also promising sources of polyphenols, especially anthocyanins. The present study focused on the changes in polyphenols from black carrot, peel, and pomace during in vitro gastrointestinal digestion. Total phenolic content (TPC), total monomeric anthocyanin content (TMAC), and total antioxidant capacity (TAC) were determined using spectrophotometric methods, whereas identification and quantification of polyphenols were carried out using UPLC-ESI-MS(E) and HPLC-DAD, respectively. TPC, TMAC, and TAC significantly decreased (23-82%) as a result of in vitro gastrointestinal digestion. Nevertheless, the amount of pomace anthocyanins released at all stages of in vitro gastrointestinal digestion was higher than black carrot anthocyanins, suggesting that pomace may be a better source of bioaccessible anthocyanins. Overall, the current study highlighted black carrot byproducts as substantial sources of polyphenols, which may be used to enrich food products.

Enzyme-Assisted Extraction Enhancing the Phenolic Release from Cauliflower (Brassica oleracea L. var. botrytis) Outer Leaves

Phenolic compounds are highly present in byproducts from the cauliflower (Brassica oleracea L. var. botrytis) harvest and are thus a valuable source for valorization toward phenolic-rich extracts. In this study, we aimed to optimize and characterize the release of individual phenolic compounds from outer leaves of cauliflower, using two commercially available polysaccharide-degrading enzymes, Viscozyme L and Rapidase. As major results, the optimal conditions for the enzyme treatment were: enzyme/substrate ratio of 0.2% for Viscozyme L and 0.5% for Rapidase, temperature 35 °C, and pH 4.0. Using a UPLC-HD-TOF-MS setup, the main phenolic compounds in the extracts were identified as kaempferol glycosides and their combinations with different hydroxycinnamic acids. The most abundant components were kaempferol-3-feruloyldiglucoside and kaempferol-3-glucoside (respectively, 37.8 and 58.4 mg rutin equiv/100 g dry weight). Incubation of the cauliflower outer leaves with the enzyme mixtures resulted in a significantly higher extraction yield of kaempferol-glucosides as compared to the control treatment.

Liquid chromatography–mass spectrometry coupled with multivariate analysis for the characterization and discrimination of extractable and nonextractable polyphenols and glucosinolates from red cabbage and Brussels sprout waste streams

Nonextractable polyphenol (NEP) fractions are usually ignored because conventional extraction methods do not release them from the plant matrix. In this study, we optimized the conditions for sonicated alkaline hydrolysis to the residues left after conventional polyphenol extraction of Brussels sprouts top (80°C, 4M NaOH, 30min) and stalks (60°C, 4M NaOH, 30min), and red cabbage waste streams (80°C, 4M NaOH, 45min) to release and characterize the NEP fraction. The NEP fractions of Brussels sprouts top (4.8±1.2mg gallic acid equivalents [GAE]/g dry waste) and stalks (3.3±0.2mg GAE/g dry waste), and red cabbage (11.5mg GAE/g dry waste) waste have significantly higher total polyphenol contents compared to their respective extractable polyphenol (EP) fractions (1.5±0.0, 2.0±0.0 and 3.7±0.0mg GAE/g dry waste, respectively). An LC-MS method combined with principal components analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) was used to tentatively identify and discriminate the polyphenol and glucosinolate composition of the EP and NEP fractions. Results revealed that phenolic profiles of the EP and NEP fractions are different and some compounds are only found in either fraction in all of the plant matrices. This suggests the need to account both fractions when analyzing the polyphenol and glucosinolate profiles of plant matrices to attain a global view of their composition. This is the first report on the discrimination of the phenolic and glucosinolate profiles of the EP and NEP fractions using metabolomics techniques.

Review on the Use of Cell Cultures to Study Metabolism, Transport, and Accumulation of Flavonoids: From Mono‐Cultures to Co‐Culture Systems

The aim of this review is to provide a comprehensive discussion on the various human/animal cell-based models used to study the absorption, transport, and metabolism of flavonoids. Flavonoids are plant-based bioactive compounds that have been extensively investigated for their active role in health alleviation and disease prevention. For this purpose, cell lines isolated from various human and animal tissues have been routinely used as an in vitro model to assess the bioavailability and bioactivity of these compounds. This paper reviews for the first time various transporters (SLCT, SGLT, bilitranslocase, and ABC transporters), metabolic routes (deglycosylation, glucuronidation, sulfation, and deconjugation), and accumulation of flavonoids in different cell lines commonly used in flavonoid research. Also, the use of co-culture systems to study flavonoid bioactivity will be discussed. To date, no definite mono-culture or co-culture formulation has been generally accepted to be the most accurate representation of the in vivo situation. Therefore, further investigation and improvement of cell-based in vitro models for flavonoid research merit further investigation.

Resveratrol improves TNF-α-induced endothelial dysfunction in a coculture model of a Caco-2 with an endothelial cell line

The bioactivity of trans-resveratrol (RSV), an important wine polyphenol, and of its metabolites was investigated in a more relevant setup comprising an in vitro coculture cell model that combines intestinal absorption and conjugation with changes in endothelial function, which is primarily affected in cardiovascular diseases. Caco-2 and endothelial EA.hy926 cells were grown in a coculture, and Caco-2 cells were treated with RSV in the coculture and in two different sequential setups for 4 h and 24 h. Transported metabolites were investigated by UPLC-MS/MSE, and the effects on NO production, ROS inhibition and secretion of vascular endothelial growth factor (VEGF), interleukin-8 (IL-8) and intercellular adhesion molecule-1 (ICAM-1) were evaluated in TNF-α-activated and nonactivated endothelial cells. RSV and four conjugated metabolites, two sulfates and two glucuronides, were identified after intestinal transport. In both coculture and sequential systems, RSV at 20 μM strongly induced NO production. Changes in ROS and NO levels demonstrated a clear effect of crosstalk between cells in the coculture. The secretion of proinflammatory cytokines and VEGF was largely increased by treatment with TNF-α (inflammatory condition). The polyphenol intervention significantly reduced the levels of VEGF, ROS, IL-8 and ICAM-1, with a more pronounced effect in TNF-α-activated endothelial cells. In conclusion, RSV and its metabolites showed accentuated bioactivity on TNF-α-induced inflammation, and the metabolism of endothelial cells as a biological target was not only influenced by these phenolics but also by the communication between distinct cell lines, showing a new perspective for investigations on polyphenol intervention and its biological outcomes.

Elastic net regularized regression for time-series analysis of plasma metabolome stability under sub-optimal freezing condition

In this paper, the stability of the plasma metabolome at −20 °C for up to 30 days was evaluated using liquid chromatography-high resolution mass spectrometric metabolomics analysis. To follow the time-series deterioration of the plasma metabolome, the use of an elastic net regularized regression model for the prediction of storage time at −20 °C based on the plasma metabolomic profile, and the selection and ranking of metabolites with high temporal changes was demonstrated using the glmnet package in R. Out of 1229 (positive mode) and 1483 (negative mode) metabolite features, the elastic net model extracted 32 metabolites of interest in both positive and negative modes. L-gamma-glutamyl-L-(iso)leucine (tentative identification) was found to have the highest time-dependent change and significantly increased proportionally to the storage time of plasma at −20 °C (R2 = 0.6378 [positive mode], R2 = 0.7893 [negative mode], p-value < 0.00001). Based on the temporal profiles of the extracted metabolites by the model, results show only minimal deterioration of the plasma metabolome at −20 °C up to 1 month. However, majority of the changes appeared at around 12–15 days of storage. This allows scientists to better plan logistics and storage strategies for samples obtained from low-resource settings, where −80 °C storage is not guaranteed.