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The present study compared and validated two analytical methods, HPLC-HRMS, and GC–MS using MSTFA as derivatization agent, for the analysis of microbiota-derived phenolic acids and aromatic compounds accumulating in urine, collected over a 24 h period after the consumption of 500 mL of orange juice. In addition, purification procedures using SDB-L and HLB solid phase cartridges were compared when HPLC-HRMS technique was used. Both HPLC-HRMS and GC–MS methodologies were successfully validated in terms of specificity, sensitivity, limit of detection and quantification, recovery and matrix effects. HPLC-HRMS, unlike GC–MS, does not require sample derivatization prior to analysis. GC–MS was not suitable for the analysis of phenolic sulfate and glucuronide metabolites because of their lack of volatility. These phase II metabolites could, however, be analysed by HPLC-HRMS which, as a consequence, provided more detailed and complete information on the phenolic compounds derived from microbiota-mediated degradation of orange juice (poly)phenols. Furthermore, the use of SDB-L and HLB cartridges for sample purification prior to HPLC-HRMS analysis is suitable for free phenolics and glucuronide metabolites but not sulfate derivatives. These findings highlight that the use of an inappropriate analytical protocol can adversely affect studies on the bioavailability of dietary (poly)phenols in which microbiota-derived phenolic catabolites play an important role.

In the present study, 27 barley genotypes (Hordeum vulgare L.) grown in two geographic origins (Czech Republic and Spain) were analysed for their contents of β-glucan, tocols and phenolic compounds (free and bound). The samples included hulled, hull-less and coloured genotypes. The results showed that concentrations of β-glucan range from 2.40 to 7.42 g/100 g. Total tocol content of the barley samples ranged between 39.9 and 81.6 μg/g. A total of 64 compounds were identified in the barley samples. These included 19 phenolic acids and aldehydes, 9 flavan 3-ols, 9 flavone glycosides, and 27 anthocyanins. The results showed a wide range of phenolic concentrations in the barley samples, highlighting the presence of considerable amounts of anthocyanins in purple barley genotypes. In synthesis, barley should be considered a good source of bioactive components, especially because of the broad spectrum of phytochemicals with potential health benefits besides the soluble fibre (β-glucan).

Artichokes are an important source of (poly)phenolic compounds, mainly caffeoylquinic acids, which consumption has been associated with health benefits. However, heat treatments have shown to affect the amounts of these bioactive food compounds. In the present study the influence of culinary techniques (boiling, griddling, and frying) on the total (poly)phenolic content of artichokes (Cynara Scolymus cv. Blanca de Tudela) was evaluated by LC-MS/MS. Additionally, the antioxidant capacity of cooked artichokes was evaluated by spectrophotometric methods. A total of 31 (poly)phenols were identified and quantified, being caffeoylquinic acids the most abundant compounds in raw artichokes accounting for more than 95% of total (poly)phenolic compounds. With the different culinary techniques, these compounds suffered degradation but also redistribution, probably due to isomerization and hydrolysis reactions. Frying and griddling showed the lowest content of (poly)phenolic compounds and antioxidant capacity suggesting thermal degradation. Boiling also provoked losses, which were mainly due to leaching of phenolic compounds into the water. However, it was the heat treatment that best preserved (poly)phenolic compounds in artichokes.

Red raspberries, containing ellagitannins and cyanidin-based anthocyanins, were fed to volunteers and metabolites appearing in plasma and urine were analysed by UHPLC-MS. Anthocyanins were not absorbed to any extent with sub nmol/L concentrations of cyanidin-3-O-glucoside and a cyanidin-O-glucuronide appearing transiently in plasma. Anthocyanins excreted in urine corresponded to 0.007% of intake. More substantial amounts of phase II metabolites of ferulic acid and isoferulic acid, along with 4′-hydroxyhippuric acid, potentially originating from pH-mediated degradation of cyanidin in the proximal gastrointestinal tract, appeared in urine and also plasma where peak concentrations were attained 1–1.5 h after raspberry intake. Excretion of 18 anthocyanin-derived metabolites corresponded to 15.0% of intake, a figure substantially higher than obtained in other anthocyanin feeding studies. Ellagitannins pass from the small to the large intestine where the colonic microbiota mediate their conversion to urolithins A and B which appeared in plasma and were excreted almost exclusively as sulfate and glucuronide metabolites. The urolithin metabolites persisted in the circulatory system and were excreted in urine for much longer periods of time than the anthocyanin metabolites although their overall urinary recovery was lower at 7.0% of intake. It is events originating in the proximal and distal gastrointestinal tract, and subsequent phase II metabolism, that play an important role in the bioavailability of both anthocyanins and ellagitannins and it is their metabolites which appear in the circulatory system, that are key to elucidating the mode of action(s) underlying the protective effects of these compounds on human health.

Heterocyclic volatile compounds present in coffee have been proposed as potent antioxidants, but their contribution to the antioxidant capacity of coffee is still unclear and controversial. The aim of this study was to assess the actual contribution of the main volatile compounds to the overall antioxidant capacity of coffee. A total of sixty-two and sixty-four volatile compounds were identified and quantified in Arabica and Robusta coffee, respectively, by static headspace-gas chromatography-mass spectrometry (SH-GC-MS). ABTS (2,2′-Azino-bi(3-ethylbenzo-thiazonile-6-sulfonic acid) diammonium salt) and DPPH (2,2-Diphenyl-1-picrylhydrazyl) antioxidant activity of the most abundant volatile heterocyclic compounds (7 furans (Fu), 3 pyrroles (Py) and 2 thiophenes (Th)), aldehydes (5) and diketones (2) was evaluated in model systems at different concentrations including those found in coffee. The model system with all the heterocyclic volatiles (Fu–Py–Th) was the most active followed by pyrroles and furans. Thiophenes were ineffective as radical scavengers at all concentrations including 100-fold, and aldehydes and ketones showed negligible activities in comparison to heterocyclic volatiles. In addition, only furans exhibited linear concentration dependent ABTS antioxidant activity and individual volatile model systems showed that only 2-methyl-tetrahydrofuran-3-one and pyrrole for ABTS, and also 1-methylpyrrole for DPPH, were the main volatile compounds responsible for the coffee antioxidant activity. However, the contribution of the heterocyclic volatile compounds to the overall antioxidant capacity of a filter coffee brew was almost insignificant, even at 100-fold concentrated Fu–Py–Th model system, accounting only for up to 3.3%.

The addition of sugar during roasting (torrefacto) has been proposed as a technique to increase the antioxidant capacity. However, other factors such as roasting degree and coffee origin also play a key role. Two batches of Colombian green coffee were roasted adding increased amounts of sucrose (0–15 g per 100 g of coffee) to reach the same roasting degree than a commercial Colombian coffee. Moreover, seven conventional roasted coffees from different origins (Colombia, Brazil, Kenya, Guatemala and Vietnam) and roasting degrees (Dark, Medium and Light), and one 100% Torrefacto roasted coffee were analyzed. Although the addition of sugar during roasting increased the DPPH quenching activity, phenolic compounds (5-caffeoylquinic, caffeic and ferulic acids, and 4-vinylguaiacol) were hardly affected by torrefacto roasting process, showing that Maillard and other roasting reactions products, such as browned-colored compounds including melanoidins (Abs 420 nm), have an important role as antioxidants. Principal Component Analysis (PCA) showed that roasting degree also plays a key role on overall antioxidant activity. Moreover, the Absorbance at 420 nm has been proposed as a good marker of torrefacto roasting process, whereas the roasting degree might be better characterized by L * values.

The aim of this work was to study the extraction behavior of the main coffee antioxidants (caffeoylquinic acids, melanoidins and caffeine) and the antioxidant capacity, during brewing time in the most widely consumed coffee brew methods (filter and espresso) in coffee. Antioxidant capacity by colorimetric assays (Folin–Ciocalteau, ABTS and DPPH) and electron spin resonance spectroscopy techniques (Fremy's salt and TEMPO) were analyzed. In espresso coffee, more than 70% of the antioxidants (except dicaffeoylquinic acids, diCQA) of a coffee brew were extracted during the first 8 s. In filter coffee, a U-shape antioxidants extraction profile was observed, starting later (after 75 s) in Vietnam coffee than in Guatemala one, probably due to different wettability. Other technological parameters, such as turbulences and a longer contact time between water and ground coffee in filter coffeemaker, increased extraction efficiency, mainly in less polar antioxidant compounds as diCQA. In conclusion, these technological factors should be considered to optimize coffee antioxidants extraction that can be used as ingredients for functional foods.