Pomegranates are one of the main highly valuable sources of ellagitannins. Despite the potential health benefits of these compounds, reliable data on their content in pomegranates and derived ...extracts and food products is lacking, as it is usually underestimated due to their complexity, diversity, and lack of commercially available standards. This study describes a new method for the analysis of the extractable and nonextractable ellagitannins based on the quantification of the acid hydrolysis products that include ellagic acid, gallic acid, sanguisorbic acid dilactone, valoneic acid dilactone, and gallagic acid dilactone in pomegranate samples. The study also shows the occurrence of ellagitannin C-glycosides in pomegranates. The method was optimized using a pomegranate peel extract. To quantify nonextractable ellagitannins, freeze-dried pomegranate fruit samples were directly hydrolyzed with 4 M HCl in water at 90 °C for 24 h followed by extraction of the pellet with dimethyl sulfoxide/methanol (50:50, v/v). The method was validated and reproducibility was assessed by means of an interlaboratory trial, showing high reproducibility across six laboratories with relative standard deviations below 15%. Their applicability was demonstrated in several pomegranate extracts, different parts of pomegranate fruit (husk, peels, and mesocarp), and commercial juices. A large variability has been found in the ellagitannin content (150–750 mg of hydrolysis products/g) and type (gallagic acid/ellagic acid ratios between 4 and 0.15) of the 11 pomegranate extracts studied.
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The health effects of (poly)phenols (PPs) depend upon their bioavailability that, in general, is very low and shows a high interindividual variability. The low bioavailability of PPs is mainly ...attributed to their low absorption in the upper gastrointestinal tract as a result of their low water solubility, their presence in foods as polymers or in glycosylated forms, and their tight bond to food matrices. Although many studies have investigated how technological and biotechnological processes affect the phenolic composition of fruits and vegetables, limited information exists regarding their effects on PP bioavailability in humans. In the present review, the effect of food processing (mechanical, thermal, and non-thermal treatments), oral-delivery nanoformulations, enzymatic hydrolysis, fermentation, co-administration with probiotics, and generation of postbiotics in PP bioavailability have been overviewed, focusing in the evidence provided in humans.
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Proanthocyanidins (PAs) were characterized in husk, membranes, arils, and seeds of ‘Mollar de Elche’ pomegranate cultivar using liquid chromatography–electrospray ionization–ion-trap tandem mass ...spectrometry after acid catalysis in the presence of phloroglucinol (phloroglucinolysis). PAs were also evaluated in commercial juice and in the juice made in the laboratory by pressing fresh arils. Pomegranate PAs were composed of a very rich mixture of flavan-3-ols: catechin, epicatechin, gallocatechin, epigallocatechin, epigallocatechin gallate, and epicatechin gallate. Catechins and gallocatechins were the most abundant units, while galloylated flavanols were detected at lower concentrations. The highest PA content was found in husk (1840.5 μg/g), followed by seeds (316.2 μg/g) and membranes (51.4 μg/g). With regard to the pomegranate edible parts, arils showed concentrations of 34.4 μg/g and pressed aril juice of 21.3 mg/L, lower than those found in other traditional PA-containing food and beverages, such as apple, grapes, chocolate, red wine, or tea. Higher concentrations similar to those found in red wine were observed in commercial whole fruit pressed pomegranate juice (146.9 mg/L). These PA concentrations represented between 0.1 and 7% of the total polyphenol content in the different pomegranate samples, which were richer in ellagitannins and anthocyanins. The mean degree of polymerization (1.2–2.1) revealed that PAs in Mollar pomegranate samples are constituted mainly of monomers and dimers, which may influence in better absorption and bioavailability of these compounds.
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Urolithins are microbial metabolites produced from ellagic acid after the intake of dietary ellagitannins by different animals. Urolithin metabolites have distinct UV spectra that enable their ...detection and differentiation by HPLC coupled with UV photodiode array detectors. Correlations between structural characteristics, including conjugation, with the UV spectra and retention times are established. The production of urolithin derivatives in different animals feeding on ellagitannins, including rodents (rats and mice), humans, pigs, squirrels, beavers, sheep, bull calves, birds, and insects, was investigated. All mammals produced urolithins, and their glucuronyl and sulfate conjugates were the main metabolites detected in plasma and urine. Unconjugated urolithins were detected in feces, ruminal content, and beaver castoreum. Different urolithin hydroxylation patterns were observed for different animal species, suggesting that the microbiota responsible for the metabolism of ellagitannins in each animal species produces dehydroxylases for the removal of specific hydroxyls from the ellagic acid residue. Metabolites were characterized using HR HPLC-TOF-MS and ion trap MS/MS. Insects and birds feeding on ellagitannin-containing foods did not produce urolithins, although they released ellagic acid. Beavers and pigs were able to produce dehydroxyellagic acid derivatives (nasutin A), showing that in some cases the removal of hydroxyl groups from the ellagic acid nucleus can be carried out before the lactone ring is opened to produce urolithins.
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The phenolic compounds of 15 strawberry cultivars grown in Spain were analyzed and quantified: anthocyanins (20.2−47.4 mg/100 g of fw) (cyanidin 3-glucoside and pelargonidin 3-glucoside, ...3-rutinoside, and 3-malonyl glucoside), flavonols (1.5−3.4 mg/100 g of fw) (quercetin 3-glucuronide and kaempferol 3-glucoside and 3-p-coumaroyl-glucoside), proanthocyanidins (53.9−163.2 mg/100 g), p-coumaroyl-glucose (0.84−6.70 mg/100 g), ellagitannins (9.67−22.86 mg/100 g) (sanguiin H-6, lambertianin C, and galloyl bis-HHDP-glucose), and ellagic acid glycosides (0.88−2.06 mg/100 g of fw) (two ellagic acid deoxyhexosides). Proanthocyanidins, the main phenolic compounds, were characterized by phloroglucinol degradation. Their mean degree of polymerization ranged from 3.4 for cv. Chiflon to 5.8 for cv. Ventana, the average value being 4.3. The terminal unit of proanthocyanidin oligomers was always (epi)catechin (17.36−29.93%) and (epi)catechin (61.66−75.39%) or (epi)afzelechin (4.50−10.54%) as extension units. Different combinations of (epi)catechin and (epi)afzelechin were detected, and their sequence of linkage was characterized by HPLC-MS-MS. Relative percentages of dimers, trimers, tetramers, and pentamers were evaluated by the extracted ion chromatogram (EIC) analysis.
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Scope
Gut microbiota converts dietary phytochemicals into metabolites and modulates their health effects. The microbial metabolism of dietary terpenoids, as the sesquiterpene lactones of leafy ...vegetables, is unknown.
Methods and Results
In vitro fermentation of lactucopicrin, lactucin, and romaine lettuce with gut microbiota from independent donors, show their extensive metabolism through untargeted metabolomics of the fecal incubations. Dehydroxylations and double bond hydrogenations are the main catabolic reactions. Isomers of dihydrolactucopicrin, tetrahydrolactucopicrin, and deoxylactucin, are observed after lactucopicrin metabolism. Tetrahydrolactucin and hexahydrolactucin are also found after lactucin metabolism. Lettuce fermentation shows similar metabolic conversions. Phase II conjugates of most of these metabolites are detected in the urine of healthy volunteers after escarole salad intake. Glucuronides, and sulfates, of dihydrolactucopicrin, tetrahydrolactucopicrin, dihydrolactucin, and deoxylactucin, are detected in the urine although with large inter‐subject variability.
Conclusion
This is the first report on the gut microbiota metabolism of sesquiterpene lactones in humans, and one of the first reports to describe that dietary terpenoids of widely consumed leafy vegetables are extensively catabolized by human gut microbiota. A large inter‐subject variation in the metabolism of sesquiterpene lactones also reflects differences in gut microbiota composition. It suggests that inter‐individual differences in their health effects should be expected.
Although the transformation of dietary phenolic compounds by human gut microbiota has been studied, the metabolism of food terpenoids remains unknown. The present study shows that lettuce and escarole terpenoids are transformed by gut microbiota into a new family of derivatives with potential biological effects that should be studied in further work.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Flavanones, flavonoids abundant in Citrus, have been shown to interfere with quorum sensing (QS) and affect related physiological processes. We have investigated the QS-inhibitory effects of an ...orange extract enriched in O-glycosylated flavanones (mainly naringin, neohesperidin, and hesperidin). The QS-inhibitory capacity of this extract and its main flavanone components was first screened using the bacteriological monitoring system Chromobacterium violaceum. We next examined the ability of the orange extract and of some of the flavanones to (i) reduce the levels of the QS mediators produced by Y. enterocolitica using HPLC-MS/MS, (ii) inhibit biofilm formation, and (iii) inhibit swimming and swarming motility. Additionally, we evaluated changes in the expression of specific genes involved in the synthesis of the lactones (yenI, yenR) and in the flagellar regulon (flhDC, fleB, fliA) by RT-PCR. The results showed that the orange extract and its main flavanone components inhibited QS in C. violaceum, diminished the levels of lactones secreted by Y. enterocolitica to the media, and decreased QS-associated biofilm maturation without affecting bacterial growth. Among the tested compounds, naringin was found to inhibit swimming motility. Exposure to the orange extract and (or) to naringin was also found to be associated with induction of the transcription levels of yenR, flhDC, and fliA. This work shows the in vitro QS-inhibitory effects of an orange extract enriched in flavanones against a human enteropathogen at doses that can be achieved through the diet and suggests that consumption of these natural extracts may have a beneficial antipathogenic effect.
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Recent studies demonstrate that fruits are rich in non-extractable polyphenols, macro-antioxidants, which have been underestimated. These are not absorbed and reach the colon where are catabolized by ...human gut microbiota releasing low molecular weight phenolics that are then absorbed efficiently. These metabolites persist in human plasma for extended times up to 3–4 days after the intake with significant concentrations. Preclinical studies with these metabolites at the concentrations that can be reached in plasma have reported anti-inflammatory and anti-oxidant effects that could be related to health benefits observed in vivo after the intake of the non-extractable macro-antioxidants.
•Non-extractable polyphenols are not absorbed and reach the colon.•Gut microbiota coverts them in small size phenolics that are better absorbed.•These metabolites persist in circulation for more than 48 h.•They show anti-inflammatory and antioxidant effects in preclinical models.•Non-extractable phenolics lead to a sustained release of bioactive metabolites.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
This study assessed 16 different honey samples in order to select the best one for therapeutic purposes. First, a study of honey’s main bioactive compounds was carried out. Then phenolic profiles ...were determined and specific compounds quantified using a HPLC system coupled to a mass spectrometer. Then, antioxidant activity, by three in vitro methods, and antibacterial activity against reference strains and clinical isolates were evaluated. Great variability among samples was observed regarding ascorbic acid (between 0.34 ± 0.00 and 75.8 ± 0.41 mg/100 g honey; p < 0.001), total phenolic compounds (between 23.1 ± 0.83 and 158 ± 5.37 mg/100 g honey; p < 0.001), and total flavonoid contents (between 1.65 ± 0.11 and 5.93 ± 0.21 mg/100 g honey; p < 0.001). Forty-nine different phenolic compounds were detected, but only 46 of them were quantified by HPLC. The concentration of phenolic compounds and the phenolic profiles varied widely among samples (between 1.06 ± 0.04 and 18.6 ± 0.73 mg/100 g honey; p < 0.001). Antioxidant activity also varied significantly among the samples. All honey varieties exhibited antibacterial activity against both reference and clinical strains (effective concentrations ranged between 0.05 and 0.40 g/mL depending on the honey sample and bacteria tested). Overall, samples with better combinations of bioactive properties were avocado and chestnut honeys.
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Untargeted metabolomics identified urinary biomarkers able to discriminate between the intake of fresh hand-squeezed and industrially processed orange juices. Processing led to an upregulation in the ...excretion of hydroxy-polymethoxyflavone sulfates, abscisic acid, and sinapic acid 4′-glucuronide. The demethylated polymethoxyflavone metabolites were produced with a significant interindividual variability suggesting that they could originate from gut microbiota metabolism. No correlation between the excretion levels of flavanone and polymethoxyflavone metabolites was observed, showing that gut microbiota metabolism differences could be behind the interindividual variability. Subjects with a high excretion level of hesperetin conjugates could be low or high polymethoxyflavone excretors. Flavanone phase II metabolites were primarily glucuronides, while those of demethylated polymethoxyflavones were mainly sulfates. A comparative study with the available demethylated polymethoxyflavone standards suggested that the metabolites produced in humans could be tentatively 4′-hydroxy- and/or 3′-hydroxy-polymethoxyflavone sulfates. This study is the first to describe the bioavailability and metabolism of citrus juice polymethoxyflavones in humans.
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