Antioxidant capacities and total polyphenol content of nine commercially available tea juices measured by an in vitro digestion model

Potential Antidiabetic Activity of Apis mellifera Propolis Extraction Obtained with Ultrasound

Recent studies have linked phenolic compounds to the inhibition of digestive enzymes. Propolis extract is consumed or applied as a traditional treatment for some diseases. More than 500 chemical compounds have been identified in propolis composition worldwide. This research aimed to determine Mexican propolis extracts' total phenolic content, total flavonoid content, antioxidant activity, and digestive enzyme inhibitory activity (ɑ-amylase and ɑ-glucosidase). In vitro assays measured the possible effect on bioactive compounds after digestion. Four samples of propolis from different regions of the state of Oaxaca (Mexico) were tested (Eloxochitlán (PE), Teotitlán (PT), San Pedro (PSP), and San Jerónimo (PSJ)). Ethanol extractions were performed using ultrasound. The extract with the highest phenolic content was PE with 15,362.4 ± 225 mg GAE/100 g. Regarding the flavonoid content, the highest amount was found in PT with 8084.6 ± 19 mg QE/100 g. ABTS•+ and DPPH• radicals were evaluated. The extract with the best inhibition concentration was PE with 33,307.1 ± 567 mg ET/100 g. After simulated digestion, phenolics, flavonoids, and antioxidant activity decreased by 96%. In contrast, antidiabetic activity, quantified as inhibition of ɑ-amylase and ɑ-glucosidase, showed a mean decrease in enzyme activity of approximately 50% after the intestinal phase. Therefore, it is concluded that propolis extracts could be a natural alternative for treating diabetes, and it would be necessary to develop a protective mechanism to incorporate them into foods.

Influence of geographic origin and tissue type on the medicinal chemical compounds of Semiliquidambar cathayensis

Semiliquidambar cathayensis is widely used in traditional Chinese medicine owing its high concentrations of polyphenol, triterpenoidic acid, and flavonoids. This study aimed to explore the impact of geographical origin and tissue type on the contents of chemical compounds of S. cathayensis, as determined by colorimetric and chromatographic methods. Therefore, we quantitively evaluated chemical compounds found in the tissues of various organs of plants collected in six different regions. Overall, we found that geographical origin affected the content of medicinal compounds in S. cathayensis leaves, with plants from Jingzhou county showing the best therapeutic potential. However, no specific correlation was observed with latitude. It is noteworthy that the amount of paeoniflorin and other compounds can be used as biomarkers of geographical origin and tissue type. Most medicinal compounds accumulated mainly in the leaves, whereas ursolic and oleanolic acids accumulated in the roots. These results show that the comprehensive medicinal value of the leaves of S. cathayensis in Jingzhou county is the highest, but the root should be selected first to collect oleanolic acid and ursolic acid.

Assessment of the Bioaccessibility of Elaeagnus angustifolia L. Flour and Its Use in Cracker Formulation

In this study, in vitro digestion of polyphenols of oleaster (Elaeagnus angustifolia L.) flour (OF) and the potential use of OF in cracker production were studied. The results showed that 21.90 mg gallic acid equivalent (GAE)/g dry matter (DM) of total polyphenol (TP), 28.15 mg rutin equivalent (RE)/g DM of total flavonoid (TF) and 7709.13 mmol ascorbic acid equivalent (AAE)/100 g DM of antioxidant capacity (AC) were found in OF. The bioaccessibility and content of the OF polyphenols and their AC during in vitro digestion varied depending on the digestion stage. The stability of the OF polyphenols was higher in gastric stage (41.92%) than intestinal one (34.01%). OF was used to replace flour in the cracker formulation at the levels of 5, 10 and 15% (w/w) and increased the TP contents and AC of the crackers compared to the sample without OF (control). The addition of OF to the cracker dough increased the bioaccessibility of the cracker polyphenols. After digestion, bioaccessibilities of enriched crackers (107.90-126.81%) were found higher than that of control sample (93.73%). However, as the level of OF in cracker increased, bioaccessibility of polyphenols decreased. The results generally indicated that oleaster has a good potential for the enrichment of foods.

Bioaccessibility and Antioxidant Capacity of Bioactive Compounds From Various Typologies of Canned Tomatoes

Tomato (Solanum lycopersicum L.) is one of the most consumed vegetables in the world; it contains high amounts of antioxidant phytochemicals and essential nutrients. Although it is commonly consumed fresh, more than 80% of its consumption derives from processed products. Since limited information on changes in the bioaccessibility of bioactive compounds during gastrointestinal digestion was reported, this current study aimed to monitor the antioxidant activity, total polyphenolic and carotenoid content, and bioaccessibility during in vitro gastrointestinal digestion of different typologies (n = 7) of canned tomatoes. A comprehensive evaluation of the polyphenolic profile of digested and not digested samples was ascertained by ultra-high-performance liquid chromatography combined with high-resolution Orbitrap mass spectrometry. The results highlighted a considerable content of rutin (1.191-9.516 mg/100 g), naringenin (0.359-1.452 mg/100 g), chlorogenic acid (1.857-11.236 mg/100 g), and lycopene (50.894-222.061 mg/kg) in the analyzed matrices. After in vitro gastrointestinal digestion, large variability, losses and low recovery were recorded. An appreciable percentage of rutin (30.7%), naringenin (29.6%), chlorogenic acid (25.8%), and lycopene (varied between 9.3 and 20%) remained bioaccessible after the in vitro gastrointestinal digestion. Our study could be a valid support to evaluate which content of bioactive compounds could be really bioaccessible to exercise beneficial effects on human health.

A combined analytical-chemometric approach for the in vitro determination of polyphenol bioaccessibility by simulated gastrointestinal digestion

In this study, an integrated characterisation through polyphenol and caffeine content and antioxidant activity was combined with chemometric analysis to assess the effects of simulated in vitro gastrointestinal digestion on the bioaccessibility of these bioactive compounds from nine different tea infusions. Tea infusions were characterised based on total flavonoids, total polyphenols and antioxidant activity, together with the determination of individual polyphenol content. Fourteen phenolic compounds, including phenolic acids, stilbenes and flavonoids, were selected based on their reported bioactivity and high accessibility, attributed to their low molecular weight. Both polyphenols and caffeine were initially monitored in raw tea infusions and through the different digestion stages (salivary, gastric and duodenal) by capillary high performance liquid chromatography coupled to diode array detection (cHPLC-DAD) and/or HPLC coupled to a triple quadrupole mass analyser (HPLC–MS/MS). Multivariate analysis of the studied bioactives, using principal component analysis and cluster analysis, revealed that the decaffeination process seems to increase the stability and concentration of the compounds evaluated during digestion. The greatest transformations occurred mainly in the gastric and duodenal stages, where low bioactivity indices (IVBA) were shown for resveratrol and caffeic acid (IVBA = 0%). In contrast, the polyphenols gallic acid, chlorogenic acid and quercetin gave rise to their availability in white, green and oolong infusion teas (IVBA > 90%). Furthermore, highly fermented black and pu-erh varieties could be designated as less bioaccessible environments in the duodenum with respect to the tested compounds.

Effects of in vitro simulated digestion on the antioxidant activity of different Camellia sinensis (L.) Kuntze leaves extracts

The stability of tea phenolic compounds is influenced by pH value and digestive processes. However, the complex mixture of constituents in tea may modulate the stability of these compounds during digestion. In this study, tea infusions obtained from green, black, and Oolong tea leaves were exposed to in vitro simulated gastrointestinal digestion, and the stability of ( +)-catechin, caffeine, (−)-epicatechin, epigallocatechin-3-gallate (EGCG), and gallic acid was compared to that of isolated compounds. Changes in antioxidant activity were also evaluated by means of DPPH assay and in a H2O2-induced in vitro oxidative stress model, using Caco-2 cells. The stability of teas antioxidant constituents was different when using teas extract, compared to the reference compound alone, with the total phenolic content being more stable in extracts containing them in higher amount. EGCG degradation correlated well with changes in the DPPH inhibition assay, confirming its pivotal role in the antioxidant activity of tea. Differently, the antioxidant effect in the in vitro cell-based model was much more related to the initial total phenolic content of the extracts, with green tea being more effective than black tea and Oolong tea. Moreover, the antioxidant activity of teas was strongly affected by gastrointestinal digestion. Taken together, these findings suggest a protective role of teas phytocomplex against gastrointestinal digestion of antioxidant constituents. In conclusion, the effect of gastrointestinal digestion on the antioxidant activity of tea should be taken into account, as this may be different from one extract to another and information on the stability of active constituents cannot be extrapolated from data obtained using single compounds.

Changes in bioactive compounds and antioxidant activity of plant-based foods by gastrointestinal digestion: a review

Phenolic compounds, omnipresent in plants, are a crucial part of the human diet and are of considerable interest due to their antioxidant properties and other potential beneficial health effects, for instance, antidiabetic, antihypertensive, anti-inflammatory, and anticancer properties. The consumption of a variety of plant-based foods containing various phenolic compounds has increased due to published scientific verification of several health benefits. The release of phenolic compounds and change in their bioactivities examined through in vitro simulated gastrointestinal digestion could provide information on the biological potency of bioactive components, which will allow us to elucidate their metabolic pathways and bioactivities at target sites. This review reports on the recent research results focused on changes during the gastro and/or intestinal phase. The effect of digestive enzymes and digestive pH conditions during simulated digestion accounted for the variations in bioaccessibility and bioavailability of phenolic antioxidants as well as the corresponding antioxidant activities were also summarized and presented in the review.

Chemoprevention of elite tea variety CFT-1 rich in EGCG against chemically induced liver cancer in rats

Camellia sinensis (L.) O. Kuntze cv. CFT-1 is an elite tea variety bred by sexual hybridization with a high content of epigallocatechin-3-gallate (EGCG) as 134.2 mg/g (which is 2.54-fold that of the common variety). This study was to evaluate the chemopreventive effects of CFT-1 green tea infusion (CFT-1) against N-nitrosodiethylamine (NDEA)-induced hepatocarcinogenesis in rats and its mechanisms. The results showed that CFT-1 had a superior inhibitory effect in NDEA-initiated hepatocarcinogenesis compared to that of common tea. CFT-1 significantly reduced the hepatic nodules incidence, size, and number and prevented the hepatic adenoma or hepatocellular carcinoma (HCC) formation. In particular, CFT-1-treated animals had the least incidence of HCC (8.33%) followed by common tea treatment (40.00%) and model control rats (87.50%). CFT-1 treatment significantly ameliorated abnormal liver function enzymes, reduced serum AFP, CEA, TSGF, and TNF-α levels, inhibited the dickkopf-related protein-1 expression, enhanced antioxidant capacity, suppressed the production of livers 8-hydroxy-2'-deoxyguanosine, and regulated hepatic phase I and II xenobiotic-metabolizing enzymes. Transcriptomic analysis of liver tissue suggested that compared to common tea, administration of CFT-1 regulated larger gene sets, which were located in several important pathways of antioxidants, inflammatory network, xenobiotic-metabolizing enzymes, apoptosis, cell proliferation, and metabolism associated with liver tumorigenesis. We identified some genes as potential molecular targets involved in the prevention of CFT-1 and found that CFT-1 inhibited inflammation response, proliferation, and accelerated apoptosis by inhibiting NF-κB and PI3K/Akt pathway. Thus, EGCG-rich CFT-1 green tea might be a potential choice for liver cancer prevention/treatment in the future.

Effect of particle size on the bioaccessibility of polyphenols and polysaccharides in green tea powder and its antioxidant activity after simulated human digestion

The bioaccessibilities of polyphenols and polysaccharides in green tea powders (GTPs) with different particle sizes of 564.24 µm, 74.85 µm, 34.62 µm and 15.10 µm and their antioxidant activities were investigated using an in vitro simulated gastrointestinal digestion model. The results showed that particle size significantly affected the bioaccessibilities of polyphenols and polysaccharides before and after digestion, except for the bioaccessibility of polysaccharides after gastric plus intestinal (GI) digestion, thus significantly affecting the antioxidant activity of GTPs. Compared with the undigested initial amount, the bioaccessibilities of polyphenols in all GTPs were approximately 59.98-71.00% after gastric digestion and 9.69-15.57% after GI digestion, and the bioaccessibilities of polysaccharides were approximately 71.10-79.51% after gastric digestion and 113.78-190.38% after GI digestion. With the decrease in particle size, the FRAP value of GTP before digestion was significantly increased and that of 15.10 µm was the largest (4.96 mmol Fe²⁺/g). Both the FRAP and DPPH values after digestion showed a trend of first increasing and subsequently decreasing; 74.85 µm GTP had the largest FRAP (4.11 mmol Fe²⁺/g) and DPPH (156.61 mg VCE/g) values after gastric digestion, and 34.62 µm GTP had the largest FRAP (0.16 mmol Fe²⁺/g) and DPPH (1.43 mg VCE/g) values after GI digestion. This study suggested that the bioaccessibilities of polyphenols and polysaccharides in GTPs and their antioxidant activity can be improved by properly reducing the particle size such that TGPs can exert more beneficial health effects.

Effect of cold plasma on blueberry juice quality

This work focusses on the effects of cold plasma, a novel, non-thermal technology, on the quality of blueberry juice, such as inactivation of Bacillus, anthocyanins, phenolics, vitamin C, antioxidant activity and color change. Oxygen concentration (0, 0.5% and 1%) of ionized gas was firstly confirmed to be the main factors for CP treatment, besides treatment time (2, 4 and 6 min). The increment of treatment time and oxygen concentration significantly promoted an increasing trend of death for Bacillus. Compared with thermal treatment, the content of phenolics was significantly increased by CP treatment, and also CP treatment could better keep the original color of blueberry juice. In terms of anthocyanin and vitamin C, relatively shorter exposure time to CP was more suggested. In antioxidant tests, increment of oxygen concentration resulted in the increasing trends of antioxidant activity in DPPH and ABTS assays.

Phenolic profile and antioxidant activity of Jasonia glutinosa herbal tea. Influence of simulated gastrointestinal in vitro digestion

In order to value J. glutinosa DC (rock tea), we characterised its phenolic profile and antioxidant activity. The study was performed in aqueous extracts before and after a simulated in vitro digestion to obtain data regarding phenolics bioavailability. Methanolic extracts were also analysed for comparison purposes. Phytochemical profiles were determined by high-performance liquid chromatography with mass spectrometric detection, whereas total phenolic content (TPC) and antioxidant assays were performed by conventional spectrophotometric methods. The most abundant compounds were dicaffeoylquinic acids, representing more than 90% of phenolics in tea infusions. Statistically significant differences were observed for all parameters except for TPC in methanol and aqueous extracts. Both phenolics amount and antioxidant activities were lower after the in vitro digestion of the infusions. However, although phenolics were lost during the simulated digestion, rock tea is still a good source of bioactive compounds with potential applications in the pharmaceutical or nutraceutical industries.

Effect of in vitro digestion on the functional properties of Psidium cattleianum Sabine (araçá), Butia odorata (Barb. Rodr.) Noblick (butiá) and Eugenia uniflora L. (pitanga) fruit extracts

This study evaluated the effect of in vitro digestion on the functional properties of three Brazilian native fruit extracts.

Antioxidant synergistic effects of Osmanthus fragrans flowers with green tea and their major contributed antioxidant compounds

The antioxidant synergistic effects of Osmanthus fragrans flowers with green tea were evaluated, and their major antioxidant compounds contributed to the total amount of synergy were determined. The antioxidant compounds in O. fragrans flowers with green tea were identified by LC-MS and quantified by UPLC-PDA. The synergistic antioxidant interactions between O. fragrans flowers with green tea and their antioxidant compounds were tested using the Prieto’s model after the simulated digestion. The main antioxidant compounds in O. fragrans flowers were acteoside and salideroside, whereas the main antioxidant compounds in green tea were caffeine, gallic acid, and L-epicatechin. The significant synergistic effect between O. fragrans flowers and green tea was observed and among nearly all of the combinations of their antioxidant compounds. Among the combinations, acteoside and gallic acid contributed most to the antioxidant synergy between O. fragrans flowers and green tea. However, the simulated digestion decreased this antioxidant synergy because it reduced the contents and the antioxidant capacities of their compounds, as well as the antioxidant synergy among the compounds.

Phytochemical content, cellular antioxidant activity and antiproliferative activity of Adinandra nitida tea (Shiyacha) infusion subjected to in vitro gastrointestinal digestion

Adinandra nitida tea (Shiyacha) is a traditional eminent and flourishing tea with a long history in Southeast Asia.

Variability in the antioxidant activity of dietary supplements from pomegranate, milk thistle, green tea, grape seed, goji, and acai: effects of in vitro digestion

The antioxidant activity (AA) of fruits and vegetables has been thoroughly investigated but less is known about the AA of dietary supplements (DS). We therefore assessed the AA of three to five DS each from pomegranate, milk thistle, green tea, grapes, goji, and acai using four widely used standard methods. The secondary objective was to determine the effects of in vitro digestion on their AA. The AA of the DS prior to digestion ranked as follows: pomegranate > resveratrol > green tea > grape seed > milk thistle and very low in goji and acai with significant group variability in AA. The AA after in vitro simulated digestion of the mouth, stomach, and small intestine compared to undigested supplement was decreased for green tea and grape seed but increased for pomegranate, resveratrol, milk thistle, goji, and acai to various extents. Although polyphenols provide the major antioxidant potency of the tested supplements, our observations indicate that digestion may alter antioxidant properties depending in part on the variations in polyphenol content.

Analytical Methods for Determining Bioavailability and Bioaccessibility of Bioactive Compounds from Fruits and Vegetables: A Review

Determination of bioactive compounds content directly from foodstuff is not enough for the prediction of potential in vivo effects, as metabolites reaching the blood system may be different from the original compounds found in food, as a result of an intensive metabolism that takes place during absorption. Nutritional efficacy of food products may be ensured by the determination of bioaccessibility, which provides valuable information in order to select the appropriate dosage and source of food matrices. However, between all the methods available, there is a need to establish the best approach for the assessment of specific compounds. Comparison between in vivo and in vitro procedures used to determine bioaccessibility and bioavailability is carried out, taking into account the strengths and limitations of each experimental technique, along with an intensive description of actual approaches applied to assess bioaccessibility of bioactive compounds. Applications of these methods for specific bioactive compound's bioaccessibility or bioavailability are also discussed, considering studies regarding the bioavailability of carotenoids, polyphenolic compounds, glucosinolates, vitamin E, and phytosterols.

Antioxidant activity of glycoprotein purified from Undaria pinnatifida measured by an in vitro digestion model

The present study was performed to investigate the chemical composition and antioxidant activity of glycoprotein purified from Undaria pinnatifida Harvey (UPGP). On SDS-PAGE, UPGP migrated as a single band with a molecular weight of approximately 10 kDa and confirmed by staining with Schiff's reagent as glycoprotein. It consists of a carbohydrate component (42.53%) and protein component (57.47%). Amino acid profile, FT-IR spectrum and enzymatic glycosylation analysis suggested that protein is linked with carbohydrate by O-glycosylation. UPGP showed dose-dependent antioxidant activities as detected by different assays before and after in vitro digestion. The IC50 values of undigested UPGP were 0.25 ± 0.03, 0.08 ± 0.005, 0.69 ± 0.12, and 0.25 ± 0.08 mg/mL for DPPH, ABTS, FRAP, and NO, respectively. Following in vitro digestion, the antioxidant activities of UPGP were decreased during the gastric phase compared to those of undigested UPGP, with an increase occurring during the duodenal phase in all assays. However, the reducing power was unchanged after in vitro digestion. Furthermore, UPGP showed protective activity against oxidative DNA damage both undigested, after saliva and duodenal phase of digestion. These results indicate that the antioxidant and DNA protection activities of UPGP may be pH-dependent and assay specific.