The effect of simulated digestion on the composition of phenolic compounds and antioxidant activities in lychee pulp of different cultivars

Simulated gastric fluid (SGF) and intestinal fluid (SIF) digestion were used to evaluate the effects of digestion on the composition of phenolic compounds and antioxidant capacities of the pulp of six lychee cultivars. Caffeic acid, ferulic acid, procyanidin B2, epicatechin, A-type procyanidin trimer, procyanidin A2, quercetin-3-rutinose-7-rhamnoside, rutin and isoquercitrin were quantified using HPLC-DAD. Lychee pulp had high concentrations of procyanidin B2 (0.30~15.53 mg g⁻¹), procyanidin A2 (0.29~0.52 mg g⁻¹) and quercetin-3-rutinose-7-rhamnoside (0.16~0.45 mg g⁻¹). SGF and SIF Digestion, which significantly decreased the concentration of procyanidin B2, epicatechin and quercetin-3-rutinose-7-rhamnoside. But observably increased the concentration of procyanidin A2. Compared with deionized water treatment (DW), the total phenolic content (TPC) and total flavonoid content (TFC) of different lychee pulps significantly increased after SGF and SIF digestion. After SGF digestion, the ferric ion reducing antioxidant power (FRAP) of lychee pulps increased while the ABTS+ free radical scavenging ability (ABTS) had a slight decline. This shows that simulated digestion improves the bioactive component and antioxidant activity of different varieties of lychee pulp.     

Effects of in vitro digestion on the composition of flavonoids and antioxidant activities of the lotus leaf at different growth stages

The lotus leaf is rich in phenolic compounds and has good antioxidant activity. The effects of simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) digestions on the active substances and antioxidant activity of the lotus leaf in different growth stages (D25, D45 and D65) were investigated. The total phenolic content of D25 and D45 significantly increased by SGF digestion but not D65 compared to the DW treatment. However, SIF treatment saw markedly increased total phenolic content across all growth stages (D25, D45 and D65). Moreover, the total flavonoid content at all growth stages was increased by SIF digestion compared to SGF treatment. The pepsin and trypsin had different effects on the FRAP and ABTS (2, 2'‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulphonic acid)) antioxidant activities of the lotus leaf. The SGF digestion increased the FRAP antioxidant capacity of the lotus leaf, and SIF digestion increased the ABTS antioxidant capacity of the lotus leaf. The HPLC results showed that the main flavonoid compound in the lotus leaf was isoquercetin. This study provides a theoretical basis for the development and utilisation of the lotus leaf as an inexpensive natural and functional food ingredient.     

Effects of in vitro simulated digestion on the free and bound phenolic content and antioxidant activity of seven species of seaweeds

The effects of simulated gastrointestinal digestion on the content and antioxidant activity of phenolics of seven seaweeds were investigated: Two methods of digestion were used – simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) to mimic the stomach and upper intestinal environment. Results showed that SIF can significantly increase the free phenolic content of all tested seaweeds. The total phenolic content of the seaweeds increased in range from 4.16 to 17.24 mg GAE/g before simulated digestion to 4.08 to 40.37 mg GAE/g after digestion. The antioxidant activity of seaweed-bound phenolics was superior to that of free phenolics. Among the seven varieties of seaweeds, Sargassum thunbergii and Sargassum kjellmanianum contained the highest content of bound phenolics after SGF digestion. Bound phenolics of Undaria pinnatifida and Sargassum thunbergii showed the highest in vitro ABTS⁺ free radical scavenging ability, while Sargassum thunbergii and Sargassum fusiforme showed the highest in vitro FRAP antioxidant activity.     

椪柑、温州蜜桔果皮中酚类物质组成及抗氧化能力研究

目的:研究椪柑、温州蜜桔果皮中酚酸与黄烷酮糖苷组成及其抗氧化能力。方法:高效液相法测定椪柑、温州蜜桔果皮中九种酚酸和两种黄烷酮糖苷的组成与含量。用福林酚法、ABTS法和FRAP法对椪柑、温州蜜桔果皮甲醇提取液抗氧化能力进行评价。结果:柑橘果皮中可溶酯化酚酸部分所占比例最大,肉桂酸型酚酸是柑橘皮中的主要酚酸,且主要以酯化形式存在,其含量排列顺序一般为:阿魏酸>对香豆酸>芥子酸>咖啡酸。温州蜜桔果皮中有较高总酚酸含量(p<0.05)。椪柑果皮主要含橙皮苷,温州蜜桔果皮含橙皮苷和少量柚皮芸香苷。温州蜜桔果皮中总黄烷酮糖苷含量高于椪柑(p<0.05)。总的来说椪柑果皮提取液抗氧化活性略高于温州蜜桔。结论:HPLC测定柑橘皮中酚酸与黄烷酮糖苷可取得良好结果,抗氧化实验表明柑橘皮具有一定的抗氧化能力。     

绿茶、橘皮、大豆中酚类物质体外消化前后稳定性及抗氧化活性的研究

本研究以富含3类代表性酚类化合物（黄烷醇、黄烷酮和异黄酮）的3种食物（绿茶、橘皮、大豆）作为原料,模拟其在人体口胃肠中的体外消化过程。采用高效液相色谱-二极管阵列检测器/电喷雾-四极杆-飞行时间串联质谱检测器（HPLC-DAD/ESI-Q-TOF-MS）检测体外消化前后酚类化合物的种类及含量变化,同时测定不同消化阶段总酚含量（TPC）、总黄酮含量（TFC）以及抗氧化活性（DPPH、ABTS、FRAP、ORAC）的变化。结果表明,绿茶提取物中检测出4种酚类化合物（表没食子儿茶素、(+)-儿茶素、表没食子儿茶素没食子酸酯和表儿茶素没食子酸酯）,大豆提取物中检测出4种酚类化合物（大豆苷、染料木苷、大豆苷元和染料木素）,橘皮提取物中检测出2种酚类化合物（柚皮苷和橙皮苷）;三种食物提取物中,经过体外消化后,绿茶提取物中的酚类化合物最不稳定,除(+)-儿茶素外,其余3种酚类物质几乎降解完全,损失率均达95%以上。绿茶、橘皮、大豆提取物的TPC在胃消化阶段显著升高（P<0.05）,在肠消化阶段显著降低（P<0.05）。绿茶提取物TFC在口腔和胃消化阶段显著升高（P<0.05）,在肠消化阶段显著降低（P<0.05）。橘皮、大豆提取物TFC与TPC变化趋势一致。绿茶提取物的四种抗氧化活性经胃肠消化后呈先升高再降低的趋势。大豆提取液体外消化前后ABTS、FRAP抗氧化活性在口腔阶段显著降低（P<0.05）,DPPH、ORAC抗氧化活性在口腔、胃消化阶段显著升高（P<0.05）,在肠消化阶段显著降低（P<0.05）。橘皮提取液ORAC抗氧化活性在肠消化阶段显著升高（P<0.05）,ABTS、FRAP抗氧化活性在体外消化阶段均表现出和总酚含量变化一致的趋势。     

Effect of in vitro‐simulated gastrointestinal digestion on the stability and antioxidant activity of blueberry polyphenols and their cellular antioxidant activity towards HepG2 cells

In this study we investigated the influence of in vitro‐simulated gastrointestinal digestion on the bioaccessibility and antioxidant activity of polyphenols from blueberries (Vaccinium spp.). Total phenolic, anthocyanin, and flavonoid content was determined, and extract and digesta compositions were analysed by HPLC‐ESI‐MS/MS. The phenolic compounds were relatively stable under a gastric environment, whereas polyphenols and anthocyanins were unstable under an intestinal environment. The bioaccessibility of polyphenol, anthocyanin, and flavonoid was greatly decreased after the intestinal digestion, and the recoveries were only 13.93%, 1.95%, and 15.68% (the IN sample), respectively. Polyphenolic profile alteration occurred during in vitro‐simulated gastrointestinal digestion. Changes of phenolic compound antioxidant activity during digestion correlated with polyphenol, flavonoid, and caffeic acid concentrations. Digested extract cellular antioxidant activity was lower than non‐digested extract activity (P < 0.05). Polyphenol dose–response correlations with cellular antioxidant activity were observed. These results indicated that in vitro‐simulated gastrointestinal digestion significantly impact polyphenols and their antioxidant activity.     

Effect of thermal processing and digestive protease on the antioxidant capacity of fruit juice–milk beverage model systems under simulated gastrointestinal digestion

The effects of thermal processing and digestive protease on the antioxidant capacity of fruit juice–milk beverage (FJMB) models containing whey protein (WP) and chlorogenic acid or catechin (CAT) under in vitro digestion were investigated. After gastric digestion, the FJMB showed a significant (P < 0.05) increase in ABTS, but little change in ferric reducing antioxidant power (FRAP). Intestinal digestion decreased the FRAP and increased ABTS except in the model containing 0.1% CAT. There were different effects (none, masking, synergistic effect) in the antioxidant activity of the WP and phenolics under digestion. Pasteurisation (63 °C/30 min) had no significant effect on the FJMB's antioxidant capacity, while sterilisation (121 °C/10 min) significantly (P < 0.05) increased, decreased or had no significant effect on ABTS and FRAP under digestion, depending on the model. Pepsin and pancreatin significantly (P < 0.05) decreased the fruit phenolics' ABTS. Ferric reducing antioxidant power was not significantly influenced by pepsin during gastric digestion, but was significantly (P < 0.05) decreased by pancreatin during intestinal digestion. These results would be helpful to improve the efficacy of fruit phenolics in FJMB subjected to thermal processing and to maintain the health benefits of this kind of functional products in the food industry.     

Spray-drying microencapsulation of pomegranate juice increases its antioxidant activity after in vitro digestion

Most of the work on pomegranate antioxidant and antibacterial activity has been carried out with solvent extracts of different plant or fruit parts. Biosensitive compounds in juice may be subject to oxidation, reducing their biological activities. Microencapsulation can be used to protect compounds, allowing its incorporation into functional foods. This study aimed at investigating antioxidant activity after in vitro digestion of microencapsulated juice. Pomegranate juice was encapsulated by spray drying its maltodextrin and gum arabic. The average diameter of the microcapsules was 10–50 µm. We evaluated the bioaccessibility of microencapsulated phenolic compounds by using an in vitro enzymatic digestion. The total phenolic content in digested microencapsulated juice was three times greater than in undigested, indicating that the compounds were made bioaccessible. Digestion also increased antioxidant activity, as measured by ABTS●+ or by DPPH●. Additionally, microencapsulated pomegranate juice showed antibacterial activity against the nine bacteria species tested.     

Stability and antioxidant activity of phenolic compounds during in vitro digestion

The impact of phenolic compounds on the human body depended on the type, content, bioavailability, and antioxidant activity. After digestion, different phenolic compounds had different changes of bioavailability and antioxidant activity, which needed to be considered in the application. In this experiment, the structural stability and antioxidant activity of 27 phenolic compounds (phenolic acids, flavonols, flavonoids, and flavanones) were investigated during the in vitro simulated digestion. This experiment eliminated the influence of food matrix, provide a basis for regularity for the changes of phenolic substances in different materials. Results showed that the bioaccessibility of phenolic compounds with different structures varied, and there was a conformational relationship between the structure and stability. After oral digestion, most of the phenolic compounds underwent degradation and the cellular antioxidant activity (CAA) values decreased to a large extent (p < 0.05). After gastric digestion, the content (p > 0.05) and CAA values (p < 0.05) of most phenolic compounds increased. However, after intestinal digestion, the phenolic compounds were degraded to a greater extent, and different structures of phenolic compounds had different changes in CAA values (p < 0.05). In general, the CAA values of most phenolic compounds after in vitro digestion were lower than the initial value. The 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ehylbenzthiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) values of phenolic acids and flavonols decreased after in vitro simulated digestion (p < 0.05), while the values of DPPH, ABTS, and FRAP of most flavonoids (p < 0.05) increased. The increased oxygen radical absorption capacity (ORAC) values were found in most phenolic acids, flavonols, and flavonoids (p < 0.05), and most flavanones showed unremarkable changes in ORAC values (p > 0.05). In general, the changing trend of chemical-based antioxidant activity was consistent with the content of phenolic compounds.     

In vitro release and antioxidant activity of Satsuma mandarin (Citrus reticulata Blanco cv. unshiu) peel flavonoids encapsulated by pectin nanoparticles

The flavonoids of citrus peel extracts (CPE) were encapsulated by pectin nanoparticles (PNs), in an attempt to control the releasing property and improve their antioxidant activity. The physiochemical properties of the obtained PNs were characterised. Flavonoid composition in CPE before and after encapsulation were determined. In vitro release profiles and antioxidant activity of CPE were further evaluated. Results showed the size of spherical PNs obtained was 271.5 ± 5.3 nm. Interestingly, in simulated gastric fluid (SGF), 73% flavonoids were released from the naked CPE after 2 h, while only 28.78% from the CPE‐loaded PNs (E‐PNs). The releasing rate of flavonoids reached 91.47% from E‐PNs after 24 h in the simulated intestinal fluid (SIF). Moreover, DPPH and ABTS assay revealed that E‐PNs showed higher antioxidant activity than blank PNs and free CPE. These data showed that the controlled release of CPE might potentially increase its bioaccessibility and there was a synergistic effect between citrus PNs and CPE on the antioxidant activity.     

Fermented coconut jelly as a probiotic vehicle,physicochemical and microbiology characterisation during an in vitro digestion

There is little information on the survival of probiotics in plant-based foods after simulated gastric and intestinal conditions, likewise the microstructure arrangement in the no-dairy fermented food. This work aimed to study if the agar–agar in a fermented coconut jelly confers protection to probiotics, phenolic and antioxidant compounds during in vitro digestion. Samples containing higher agar–agar amounts tend to retain (P < 0.05) antioxidant and phenolic compounds in their network better, even after the in vitro digestion. Also, a compact and homogeneous microstructure was observed by the Confocal Laser Scanning Microscopy. The texture profile analysis shows that 1% of agar samples presented the maximum hardness (P < 0.05) due to more bonding points and intermolecular interactions. Finally, the survival of probiotics remained above the recommended values (10⁶–10⁷ CFU g⁻¹) after the in vitro digestion of a product with probiotic potential.     

In vitro antioxidant activity and phenolic profiles of tropical fruit by-products

Peel and seeds of red-skinned passion fruit, mango, longan, rambutan, white-flesh and red-flesh dragon fruit were screened for their in vitro antioxidant activity, and determination of a detailed profile of phenolic compounds. Rambutan peel and mango seed extracts exhibited the highest total phenolic content and antioxidant activities (DPPH, ABTS and FRAP values). By using UPLC-QTOF-MS/MS analysis, the profiles of soluble and bound phenolics in the fruit by-products were obtained. Ellagic acid, geraniin, quercetin hexoside, gallic and galloyshikimic acid were predominant in rambutan peel, whereas, mangiferin, ellagic acid and galloy(di)glucoside were the major phenolic compounds in mango seed. Main phenolic compounds in longan peel were ellagic acid, galloyldiglucoside, and gallic acid, while in dragon fruit peel this was isorhamnetin glycoside, isorhamnetin glucorhamoside. Meanwhile, rutin and quercetin hexoside were predominant in passion fruit peel. These findings contribute significantly to the database of phenolic profiles of by-products of tropical fruits.     

Phenolic contents,antioxidant activities and potential bioaccessibilities of industrial pomegranate nectar processing wastes

Antioxidant potential and bioaccessibility of co‐products from industrial pasteurised pomegranate nectar (PN) processing such as peel (PP), press cake (PC) and precipitate after clarification (PAC) in comparison with raw material (arils) and final products (CON and PN) were determined. Total phenolic (TPC), flavonoid (TFC), anthocyanin (TAC), tannin contents (TTC) and antioxidant activity (TAA) were determined besides identifying major phenolics and investigating in vitro bioaccessibility after gastrointestinal (GI) digestion. PP showed the highest values, except for TAC. Phenolics (12.7–43.0%) were found to be more stable than anthocyanins (0.6–2.1%) after in vitro GI digestion. PAC was found to be a better source for anthocyanins than CON and also showed higher phenolic bioaccessibility (28.8%) than PN (19.6%). PC and PAC possessed as much TPC, TFC, TTC and TAA levels as CON, with some exceptions. Therefore, these results indicated that not only PP but also PC and PAC should be valorised as a good source for phenolics and anthocyanins.     

Stability and antioxidant activity of anthocyanins from purple sweet potato (Ipomoea batatas L. cultivar Eshu No. 8) subjected to simulated in vitro gastrointestinal digestion

The study was aimed to investigate the stability and antioxidant activities of anthocyanins obtained from purple sweet potato via an in vitro digestion system. Three fractions of anthocyanin-rich extracts were obtained via ODS packing column. Anthocyanins and copigment (primary phenolic acids) of fraction 2 were investigated during simulated an in vitro gastrointestinal digestion. Anthocyanins and copigment were recognised by UPLC-LTQ-MS/MS. Besides, anthocyanins were found effectively stable under the acidic gastric digestion conditions. However, the anthocyanins recovery was greatly decreased at around 10% after intestinal digestion. An association between the type, number of acylated group and stability to intestinal digestion was found. Di-acylated anthocyanins possessed higher stability compared with mono-acylated anthocyanins and the stability of acylated group in digestion process followed the order of p-hydroxybenzoyl > feruloyl > caffeoyl. However, there was no much difference in copigment content which was found during digestion process. Moreover, the radical scavenging ability and xanthine oxidase (XO) inhibition showed that the digestion products possessed good biological activities mainly due to its anthocyanin composition.     

Stability of the phenolic compounds and antioxidant capacity of five fruit (apple,orange, grape,pomelo and kiwi) juices during in vitro‐simulated gastrointestinal digestion

The in vitro digestive stability of phenolic compounds and the antioxidant capacity of five kinds of commonly consumed fruit juices in the daily diet, including apple juice (AJ), orange juice (OJ), grape juice (GJ), pomelo juice (PJ) and kiwifruit juice (KJ), were studied. Following in vitro digestion, the total phenolic (TP) content of fruit juices decreased to different extents by 35%, 25.3%, 23.5%, 22.2% and 7.8% for KJ, OJ, PJ, GJ and AJ, respectively. The individual phenolic content showed similar changes to the TP content, showing reductions of naringenin‐trisaccharide in OJ and PJ, epicatechin in GJ, and chlorogenic acid in AJ by 43.74%, 27.59%, 47.11% and 33.28%, respectively. Conversely, the antioxidant capacity of fruit juices during digestion measured by ABTS assay increased from 4.79% to 35.53%, except in KJ, which decreased by 19.34%. These results show the health benefits of fruit juices after processing and contribute towards establishing suitable dietary recommendations.     

Antioxidant and Free Radical Scavenging Capacity of Extensively Used Medicinal Plants in Sri Lanka

The burden of chronic diseases is rapidly increasing worldwide. Diet and nutrition are important factors in the promotion and maintenance of good health throughout the entire life course. Physiological and biochemical alterations in the human body may result in overproduction of free radicals leading to oxidative damage to biomolecules (e.g. lipids, proteins, DNA). Use of medicinal plant based products has increased recently because of their exerted beneficial properties such as antioxidant, anticancer, hypoglycaemic and hypolipidaemic activities. The present study was designed to assess the in vitro antioxidant activity and free radical scavenging capacity of ten medicinal plants which are extensively used in the Ayurvedic treatment systems in Sri Lanka. Water extracts were prepared and evaluated for their free-radical scavenging capacity and antioxidant activity using a number of chemical assays; DPPH, ABTS and FRAP. The total Phenolic (TPC) and Total Flavonoid Content (TFC) were also assessed. The TPC and TFC values of the extracts varied from 295.94±3.65 – 5.22±0.08 (mg Gallic Acid Equivalent (GAE)/g dry weight) and 115.01±1.69 – 0.97±0.002 (mg Catechin Equivalent (CE)/g dry weight) respectively. The DPPH and ABTS radical scavenging activities were higher for the Nelli (Phyllanthus emblica) extract while the least activity was observed in Venivel (Cosciniumfenestratum) extract. The FRAP activity of the extracts was well proved with the DPPH and ABTS radical scavenging activities. A positive, significant linear relationship between antioxidant activity and TPC and TFC content showed that phenolic compounds and flavonoids were the dominant antioxidant components in the medicinal herbs studied.     

Effect of in vitro gastrointestinal digestion on the antioxidant activity of protein hydrolysates prepared from Cape hake by‐products

The antioxidant activity of fish protein hydrolysates may change in the digestive tract during the human gastrointestinal digestion depending on their preparation conditions. Thus, the objective of this study was to assess the antioxidant properties of Cape hake hydrolysates prepared by three different methods (HPH‐A, HPH‐B and HPH‐C) and the effect of their in vitro gastrointestinal digestion on their antioxidant properties. HPH‐A showed the highest reducing power, while HPH‐B and HPH‐C exhibited the highest OH antiradical activity. Fe²⁺‐chelating activity was similar for all hydrolysates, but HPH‐C had a higher Cu²⁺‐chelating activity comparable to that of EDTA. The in vitro gastrointestinal digestion of hydrolysates caused a decrease in the DPPH inhibition, but an increase in scavenging ABTS in all hydrolysates. Copper‐ and iron‐chelating activities increased after digestion of hydrolysates. The results showed that the gastrointestinal digestion of HPHs generally increased their antioxidant properties.     

Effect of addition of Agaricus blazei mushroom residue to milk enriched with Omega‐3 on the prevention of lipid oxidation and bioavailability of bioactive compounds after in vitro gastrointestinal digestion

The residue from a hydroalcoholic extract of the mushroom Agaricus blazei (MAR) was evaluated for phenolic compounds, flavonoids and antioxidant activity. The ability of MAR to slow the oxidation of Omega‐3 resulting from light exposure in milk matrix, and its bioavailability after in vitro digestion was investigated. MAR presented phenolic compounds and flavonoids and showed antioxidant activity. At each concentration, addition of MAR to Omega‐3‐supplemented milk inhibited the production of conjugated dienes and malonaldehyde compared with samples without MAR. The bioavailability assay showed that polyphenols were still present after in vitro digestion and had antioxidant activity.     

Evaluation of antioxidant activity of olive leaf extract obtained by ultrasound-assisted extraction and their antimicrobial activity against bacterial pathogens from food

The aim of the present study was to evaluate and compare the phenolic content and antioxidant and antimicrobial properties of olive leaf extracts obtained by ultrasound-assisted extraction (UAE) and conventional extraction (CSE). UAE of olive leaf extracts yielded a higher total phenolic content (TPC) and total flavonoid content (TFC) of 14.31% and 19.50%, respectively. Higher antioxidant activities were found from the extracts prepared with UAE (for 18.5%, 12.5%, 10.9% and 17.6% higher determined by DPPH, ABTS, FRAP and CUPRAC methods, respectively). Good antibacterial inhibitory activity (as MIC and MBC) was observed against both Y. enterocolitica and S. aureus (1.40 ± 0.40 mg mL⁻¹ and 4.00 ± 1.60 mg mL⁻¹, respectively) with the extract prepared with UAE. In conclusion, olive leaf extracts prepared with UAE exhibited higher antioxidant and antimicrobial activities against common food-borne pathogens than CSE extracts and thus could be beneficial in ensuring food quality and food safety.     

Characterisation and comparison of phenols,flavonoids and isoflavones of soymilk and their correlations with antioxidant activity

To investigate the relationship between bioactive compounds and antioxidant property, total phenolic content (TPC), total flavonoid content (TFC), individual and total isoflavone content of soymilk and their correlations with oxygen‐radical‐absorbing capacity (ORAC), ferric reducing antioxidant power (FRAP) and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging capacity values were evaluated and compared. Results showed that TPC, TFC, isoflavones (including concentration and profiles) and antioxidation activity significantly varied among ten tested soybean cultivars. Significant correlations were established between DPPH and TFC (r = 0.553, P < 0.01), DPPH and TPC (r = 0.753, P < 0.01), FRAP and TFC (r = 0.599, P < 0.01) and FRAP and TPC (r = 0.616, P < 0.01). Positive linear correlations were found between subtotal, total isoflavones and ORAC. Unlike other isoflavone monomers, aglycone isoflavones correlated positively with DPPH and FRAP significantly. DPPH well correlated with FRAP, whereas neither DPPH nor FRAP correlated with ORAC. TPC, TFC, individual and total isoflavone values are potentially useful for soymilk antioxidant activity assessment.