Direct absorption of acylated anthocyanin in purple-fleshed sweet potato into rats

Accumulation patterns of flavonoids and phenolic acids in different colored sweet potato flesh revealed based on untargeted metabolomics

Sweet potatoes are rich in flavonoids and phenolic acids, showing incomparable nutritional and health value. In this investigation, we comprehensively analyzed the secondary metabolite profiles in the flesh of different-colored sweet potato flesh. We determined the metabolomic profiles of white sweet potato flesh (BS), orange sweet potato flesh (CS), and purple sweet potato flesh (ZS) using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The CS vs. BS, ZS vs. BS, and ZS vs. CS comparisons identified a total of 4447 secondary metabolites, including 1540, 1949, and 1931 differentially accumulated metabolites. Among them, there were significant differences in flavonoids and phenolic acids. There were 20 flavonoids and 13 phenolic acids that were common differential metabolites among the three comparison groups. The accumulation of paeoniflorin-like and delphinidin-like compounds may be responsible for the purple coloration of sweet potato flesh. These findings provide new rationale and insights for the development of functional foods for sweet potatoes.

List of compounds

Kaempferol (PubChem CID: 5280863); Peonidin 3-(6"-p-coumarylglucoside) (PubChem CID: 44256849); Swerchirin (PubChem CID: 5281660); Trilobatin (PubChem CID: 6451798); 3-Geranyl-4-hydroxybenzoate (PubChem CID: 54730540); Eupatorin (PubChem CID: 97214); Icaritin (PubChem CID: 5318980); Isorhamnetin (PubChem CID: 5281654); Glucoliquiritin apioside (PubChem CID: 74819335); Brazilin (PubChem CID: 73384).

Antitumor Activity of the Xanthonoside XGAc in Triple-Negative Breast, Ovarian and Pancreatic Cancer by Inhibiting DNA Repair

Dysregulation of the DNA damage response may contribute to the sensitization of cancer cells to DNA-targeting agents by impelling cell death. In fact, the inhibition of the DNA repair pathway is considered a promising anticancer therapeutic strategy, particularly in combination with standard-of-care agents. The xanthonoside XGAc was previously described as a potent inhibitor of cancer cell growth. Herein, we explored its antitumor activity against triple-negative breast cancer (TNBC), ovarian cancer and pancreatic ductal adenocarcinoma (PDAC) cells as a single agent and in combination with the poly(ADP-ribose) polymerase inhibitor (PARPi) olaparib. We demonstrated that XGAc inhibited the growth of TNBC, ovarian and PDAC cells by inducing cell cycle arrest and apoptosis. XGAc also induced genotoxicity, inhibiting the expression of DNA repair proteins particularly involved in homologous recombination, including BRCA1, BRCA2 and RAD51. Moreover, it displayed potent synergistic effects with olaparib in TNBC, ovarian cancer and PDAC cells. Importantly, this growth inhibitory activity of XGAc was further reinforced in a TNBC spheroid model and in patient-derived ovarian cancer cells. Also, drug-resistant cancer cells showed no cross-resistance to XGAc. Additionally, the ability of XGAc to prevent cancer cell migration was evidenced in TNBC, ovarian cancer and PDAC cells. Altogether, these results highlight the great potential of acetylated xanthonosides such as XGAc as promising anticancer agents against hard-to-treat cancers.

Cellular uptake of anthocyanins extracted from black soybean, grape, and purple sweet potato using INT-407 cells

This study combined in vitro digestion and INT-407 cells to evaluate the bioaccessibility of anthocyanins in the small intestinal epithelial cells. Black soybean, grape, and purple sweet potato were chosen as they have a different anthocyanin composition. After the aqueous extract was digested under in vitro gastric and intestinal conditions, the digested mixture was incubated in the media of INT-407 for 2 h at 37 °C. Low proportion (< 0.3%) of anthocyanins in black soybean and grape passed through cell membranes. Cyanidin-3-O-glucoside and pelargonidin-3-O-glucoside in black soybean and cyanidin-3-O-(6-O-p-coumaroyl)-5-O-diglucoside and delphinidin-3-O-(6-O-p-coumaroyl)-5-O-diglucoside in grape were found inside the cell. However, acylated anthocyanins containing three sugar moieties in purple sweet potato were not detected inside the cell. p-Coumaric acid was detected in the cells incubated with grape, but not in the media. These indicate that chemical structure of anthocyanins affected their cellular uptake and antioxidant activity in INT-407 cells.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-021-00976-y.

Acylated anthocyanins: A review on their bioavailability and effects on postprandial carbohydrate metabolism and inflammation

Anthocyanins, the natural red and purple colorants of berries, fruits, vegetables, and tubers, improve carbohydrate metabolism and decrease the risk factors of metabolic disorders, but their industrial use is limited by their chemical instability. Acylation of the glycosyl moieties of anthocyanins, however, changes the chemical properties of anthocyanins and provides enhanced stability. Thus, acylated anthocyanins are more usable as natural colorants and bioactive components of innovative functional foods. Acylated anthocyanins are common in pigmented vegetables and tubers, the consumption of which has the potential to increase the intake of health-promoting anthocyanins as part of the daily diet. For the first time, this review presents the current findings on bioavailability, absorption, metabolism, and health effects of acylated anthocyanins with comparison to more extensively investigated nonacylated anthocyanins. The structural differences between nonacylated and acylated anthocyanins lead to enhanced color stability, altered absorption, bioavailability, in vivo stability, and colonic degradation. The impact of phenolic metabolites and their potential health effects regardless of the low bioavailability of the parent anthocyanins as such is discussed. Here, purple-fleshed potatoes are presented as a globally available, eco-friendly model food rich in acylated anthocyanins, which further highlights the industrial possibilities and nutritional relevance of acylated anthocyanins. This work supports the academic community and industry in food research and development by reviewing the current literature and highlighting gaps of knowledge.

De novo biosynthesis of tyrosol acetate and hydroxytyrosol acetate from glucose in engineered Escherichia coli

Tyrosol and hydroxytyrosol derived from virgin olive oil and olives extract, have wide applications both as functional food components and as nutraceuticals. However, they have low bioavailability due to their low absorption and high metabolism in human liver and small intestine. Acetylation of tyrosol and hydroxytyrosol can effectively improve their bioavailability and thus increase their potential use in the food and cosmeceutical industries. There is no report on the bioproductin of tyrosol acetate and hydroxytyrosol acetate so far. Thus, it is of great significance to develop microbial cell factories for achieving tyrosol acetate or hydroxytyrosol acetate biosynthesis. In this study, a de novo biosynthetic pathway for the production of tyrosol acetate and hydroxytyrosol acetate was constructed in Escherichia coli. First, an engineered E. coli that allows production of tyrosol from simple carbon sources was established. Four aldehyde reductases were compared, and it was found that yeaE is the best aldehyde reductase for tyrosol accumulation. Subsequently, the pathway was extended for tyrosol acetate production by further overexpression of alcohol acetyltransferase ATF1 for the conversion of tyrosol to tyrosol acetate. Finally, the pathway was further extended for hydroxytyrosol acetate production by overexpression of 4-hydroxyphenylacetate 3-hydroxylase HpaBC.

Effect of Agave Fructans as Carrier on the Encapsulation of Blue Corn Anthocyanins by Spray Drying

Effects of agave fructans as carrier agents on the encapsulation of blue corn anthocyanins using spray-drying were evaluated. Blue corn extract was mixed with 6%, 8%, 10%, and 12% (w/v) of agave fructans in duplicate and dried at 150 °C. The extract showed good contents of anthocyanins, polyphenols, and antioxidant activity. The increase of agave fructans in the encapsulated powders caused a significant increase (p < 0.05) in the humidity, water activity (aw), pH, bulk density, water solubility index (WSI), and color L* values. On the contrary, the agave fructan addition decreased the hygroscopicity, water absorption index (WAI), antioxidant activity, total anthocyanin, total polyphenol, and individual anthocyanin contents. The encapsulation of blue corn extract with 6% agave fructans (w/v) resulted in good physical, thermal, morphological, and high antioxidant properties. The results suggest that the use of agave fructans as wall material represents advantages in the conservation of anthocyanins and other bioactive compounds from blue corn extract during their encapsulation. The application of blue corn anthocyanin encapsulated powders as a food ingredient is promising for food pigmentation, representing additional advantages for their contribution as a soluble fiber that can benefit the health of consumers.

Acid Inhibition on Polyphenol Oxidase and Peroxidase in Processing of Anthocyanin-Rich Juice and Co-product Recovery from Purple-Fleshed Sweetpotatoes

With high phytochemical and starch contents, purple-fleshed sweetpotatoes (PFSP) have been processed into various functional ingredients and food products including juices and natural colorants. For juice processing, PFSP are usually subjected to heat treatment for inactivation of pigment-degrading enzymes. However, heating of sweetpotatoes gelatinizes starch and produces thick slurry with cooked flavor, which are the drawbacks. Development of alternative processes to overcome the stated problems will be beneficial to sweetpotato processors. This study demonstrated that acidified water (≥3% w/v citric acid) was effective in inhibiting polyphenol oxidase and peroxidase in raw PFSP resulting in an attractive reddish juice. About 93% total phenolics (TP) and 83% total monomeric anthocyanins (TMA) in PFSP were extracted by two repeated extractions. The combined PFSP juice (3.2 L/kg PFSP) had high levels of TP (1,850 mg/L) and TMA (475 mg/L). With the developed process, 167 g dried starch, and 140 g dried high-fiber pomace were obtained for each kg raw PFSP, besides the highly pigmented juice. Pasteurization of the PFSP juice samples (pH 3.2) at 80 °C for 12 s resulted in 15% loss in TMA and had no effect on TP. The results indicated an efficient process to produce sweetpotato juice with high bioactive compounds and recovery of starch and high dietary fiber pomace as co-products. PRACTICAL APPLICATION: Purple-fleshed sweetpotatoes (PFSP) are rich in polyphenolics and antioxidant activities. In PFSP juice extraction, heat treatment to inactivate the pigment-degrading enzymes results in starch gelatinization and cooked flavor. A nonthermal process using acidified water was developed for producing anthocyanin-rich juice from PFSP and concurrently recovering native starch and dried pomace, which would increase the economic feasibility of the developed process. The results demonstrate an efficient process for the sweetpotato industry in producing PFSP pigmented juice and co-products for various food applications.

Effect of domestic cooking methods on the anthocyanins and antioxidant activity of deeply purple-fleshed sweetpotato GZ9

Purple-fleshed sweetpotatoes (PFSPs) are considered to be a healthy food and there are many methods to process in family. This study aimed to investigate the effects of various domestic cooking on the anthocyanin variation and antioxidant activity of a newly bred purple-fleshed cultivar Guangzishu 9 (GZ9) with anthocyanin content up to 1,500 mg/100g dry weight. As a result, total 15 individual anthocyanins were separated and identified by using UPLC-QTOF-MS. Top three anthocyanins were cyanidin 3-dicaffeoyl sophoroside-5-glucoside, cyanidin 3-caffeoyl- p-coumaryl sophoroside-5-glucoside and peonidin 3-caffeoyl-p-hydroxybenzoyl sophoroside-5-glucoside, which accounting for 57.27% of the total anthocyanin content. Acylated anthocyanins were the major constituents in GZ9, and the type of anthocyanins was dominated by cyanidin. Boiling, steaming and mircrowaving had no significant effect on the total anthocyanin content. But baking, frying, air-frying and stir-frying reduced 11–45% of total anthocyanin content. Through ABTS⁺ radical scavenging capacity and reducing power, antioxidant variations were also observed during different family cooking, and the variation had a strong correlation with total anthocyanin content.

Comparative Study on the Chemical Structure and In Vitro Antiproliferative Activity of Anthocyanins in Purple Root Tubers and Leaves of Sweet Potato ( Ipomoea batatas)

The structure and in vitro antiproliferative activity of anthocyanins in the root tubers of a sweet potato variety cv. Bhu Krishna and the purple leaves of a promising accession S-1467 were studied with the objectives of understanding the structure-activity relationship and comparing the leaf and tuber anthocyanins. The chemical structure of anthocyanins was determined by high-resolution electrospray ionization mass spectrometry analysis. A fluorescence-resonance-energy-transfer-based caspase sensor probe had been used to study the antiproliferative property, and analysis of the cell cycle was performed after staining with propidium iodide and subsequent fluorescence-activated cell sorting. Structurally, the anthocyanins in root tubers were identical to those in leaves, but there was a difference in the proportion of various aglycones present in both. This has led to distinguishable differences in the antiproliferative activity of leaf and tuber anthocyanins to various cancer cells. All nine anthocyanins were found in acylated forms in both tubers and leaves. However, peonidin derivatives were major anthocyanins in tubers (33.98 ± 1.41 mg) as well as leaves (27.68 ± 1.07 mg). The cyanidin derivatives were comparatively higher in leaves (20.55 ± 0.91 mg) than tubers (9.44 ± 0.94 mg). The tuber and leaf anthocyanins exhibited potential antiproliferative properties to MCF-7, HCT-116, and HeLa cancer cells, and the structure of anthocyanins had a critical role in it. The leaf anthocyanins exhibited significantly higher activity against colon and cervical cancer cells, whereas tuber anthocyanins had a slightly greater effect against breast cancer cells.

Discovery of a New Xanthone against Glioma: Synthesis and Development of (Pro)liposome Formulations

Following our previous work on the antitumor activity of acetylated flavonosides, a new acetylated xanthonoside, 3,6-bis(2,3,4,6-tetra-O-acetyl-β-glucopyranosyl)xanthone (2), was synthesized and discovered as a potent inhibitor of tumor cell growth. The synthesis involved the glycosylation of 3,6-di-hydroxyxanthone (1) with acetobromo-α-d-glucose. Glycosylation with silver carbonate decreased the amount of glucose donor needed, comparative to the biphasic glycosylation. Xanthone 2 showed a potent anti-growth activity, with GI₅₀ < 1 μM, in human cell lines of breast, lung, and glioblastoma cancers. Current treatment for invasive brain glioma is still inadequate and new agents against glioblastoma with high brain permeability are urgently needed. To overcome these issues, xanthone 2 was encapsulated in a liposome. To increase the well-known low stability of these drug carriers, a proliposome formulation was developed using the spray drying method. Both formulations were characterized and compared regarding three months stability and in vitro anti-growth activity. While the proliposome formulation showed significantly higher stability, it was at the expense of losing its biocompatibility as a drug carrier in higher concentrations. More importantly, the new xanthone 2 was still able to inhibit the growth of glioblastoma cells after liposome formulation.

Rutin derivatives obtained by transesterification reactions catalyzed by Novozym 435: Antioxidant properties and absence of toxicity in mammalian cells

Flavonoids are one of the most important and diversified phenolic groups among products of natural origin. An important property of this metabolite class is the antioxidant action. This study evaluated the antioxidant and cytotoxic activities and oxidative stress of transesterification products of the flavonoid rutin, catalyzed by Novozym^® 435. The presence of monoacetate and diacetate was confirmed by quantitative evaluation of the retention times (rutin, 15.68 min; rutin monoacetate, 18.14 min; and rutin diacetate, 18.57 min) and by the data from LC-MS and NMR ¹H and ¹³C. The experiment showed excellent conversion values of 96% in total acetates (rutin monoacetate and diacetate). These results confirmed that rutin derivatives have antioxidant potential, as evaluated by the ORAC method (rutin standard: 0.53 ± 0.08 μM Trolox/g and rutin derivatives: 2.33 ± 1.08 μM Trolox/g) and also show low cytotoxicity in human and animal cells. Rutin derivatives reduced the production of reactive oxygen species in RAW macrophages as well. Many qualities attributed to rutin derivatives make them promising potential candidates for use as nutraceuticals, including their high amounts of antioxidants, biological potential and low toxicity, which contribute to the reduction of oxidative stress.

Purple sweet potato anthocyanin exerts antitumor effect in bladder cancer

Bladder cancer (BC) is the most common malignant disease. The developing of economically sustainable and available agents for the treatment of BC is required. Purple sweet potato anthocyanin (PSPA) has been shown to have antitumor abilities. The present study aimed to evaluate the potential role of PSPA in BC treatment. CCK-8 assay was used to assess the viability of BC cells. Flow cytometry assays were performed to evaluate the mitochondrial membrane potential (MMP), cell apoptosis and cell-cycle distribution. Real-time PCR (RT-PCR) and western blot analysis were performed to determine the expression of the target genes. The results of this study revealed that PSPA reduced the viability of BC in a dose-dependent manner. The MMP collapse was aggravated by the PSPA treatment. The apoptosis rate was higher in the PSPA groups than that in the control group. The expression of the pro-apoptosis genes, including cleaved caspase-3, Fas, Fasl, Bcl-2-associated X proteins (Bax) and anti-apoptotic gene (Bcl-2) was induced and decreased by PSPA, respectively. The cell-cycle progression was suppressed by the presence of PSPA. The activation of the phosphatidylinositol-4,5-bisphosphate 3-kinase/Akt (PI3K/Akt) signaling pathway was suppressed by PSPA treatment during BC treatment. The PI3K/Akt signaling was closely related to the antitumor effect of PSPA in BC. The present study provided evidence regarding the treatment of BC and enhanced the understanding of the potential role that PSPA plays in cancer prevention.

Synthesis of New Glycosylated Flavonoids with Inhibitory Activity on Cell Growth

Natural flavonoids and xanthone glycosides display several biological activities, with the glycoside moiety playing an important role in the mechanism of action of these metabolites. Herein, to give further insights into the inhibitory activity on cell growth of these classes of compounds, the synthesis of four flavonoids (5, 6, 9, and 10) and one xanthone (7) containing one or more acetoglycoside moieties was carried out. Acetyl groups were introduced using acetic anhydride and microwave irradiation. The introduction of one or two acetoglycoside moieties in the framework of 3,7-dihydroxyflavone (4) was performed using two synthetic methods: the Michael reaction and the Koenigs-Knorr reaction. The in vitro cell growth inhibitory activity of compounds 5, 6, 7, 9, and 10 was investigated in six human tumor cell lines: A375-C5 (malignant melanoma IL-1 insensitive), MCF-7 (breast adenocarcinoma), NCI-H460 (non-small cell lung cancer), U251 (glioblastoma astrocytoma), U373 (glioblastoma astrocytoma), and U87MG (glioblastoma astrocytoma). The new flavonoid 3-hydroxy-7-(2,3,4,6-tetra-O-acetyl-β-glucopyranosyl) flavone (10) was the most potent compound in all tumor cell lines tested, with GI₅₀ values < 8 μM and a notable degree of selectivity for cancer cells.

Double-blind, placebo-controlled pilot trial of anthocyanin-rich purple sweet potato beverage on serum hepatic biomarker levels in healthy Caucasians with borderline hepatitis

The objective is to evaluate the efficacy of anthocyanin-rich purple-fleshed sweet potato (PSP) beverage on the serum levels of gamma-glutamyl transferase (GGT), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in healthy Caucasians with borderline hepatitis. Forty healthy Caucasians (41-69 years) consumed three bottles of the PSP beverage (177 mg anthocyanins per 125-ml bottle) or placebo (1.3 mg) per day for 8 weeks. Thirty-nine subjects completed the study and two subjects were excluded from statistical analysis. GGT levels in the PSP group on days 15 and 43 were lower (P=0.077 and 0.038, respectively), AST levels in the PSP group on days 29 and 43 were lower (P=0.010 and 0.045, respectively) and ALT level in the PSP group on day 43 was lower (P=0.037) than in the placebo group. The PSP beverage did not induce clinically relevant changes in other blood and clinical chemistry parameters.

Effect of consuming a purple-fleshed sweet potato beverage on health-related biomarkers and safety parameters in Caucasian subjects with elevated levels of blood pressure and liver function biomarkers: a 4-week, open-label, non-comparative trial

An open-label study with one treatment arm was conducted to investigate changes in health-related biomarkers (blood pressure and liver enzyme activity) and the safety of 4 weeks of consuming a purple-fleshed sweet potato beverage in Caucasian subjects. Twenty healthy adults, 18-70 years of age, with a body mass index >25 kg/m(2), elevated blood pressure and elevated levels of liver function biomarkers consumed two cartons of purple-fleshed sweet potato beverage (125 ml, including 117 mg anthocyanin per carton) daily for 4 weeks. Hematology, serum clinical profile, dipstick urinalysis and blood pressure were determined before consumption, at 2 and 4 weeks of consumption and after a 2-week washout period. A trend was found toward lowering systolic blood pressure during the treatment period (p=0.0590). No significant changes were found in diastolic blood pressure throughout the study period. Systolic blood pressure was significantly lower after 4 weeks of consumption compared with before consumption (p=0.0125) and was significantly higher after the 2-week washout period compared with after consumption (p=0.0496). The serum alanine aminotransferase level significantly increased over time, but aspartate aminotransferase and γ-glutamyltransferase levels stayed within the normal range of reference values. Safety parameters of the blood and urine showed no clinically relevant changes. The consumption of a purple-fleshed sweet potato beverage for 4 weeks resulted in no clinically relevant changes in safety parameters of the blood and urine and showed a trend toward lowering systolic blood pressure.

Effect of drying conditions on properties, pigments and antioxidant activity retentions of pretreated orange and purple-fleshed sweet potato flours

Pigmented sweet potatoes (SPs) are outstanding sources of anthocyanin, β-carotene and other color-related phytonutrients. However, fresh SP roots are highly perishable and difficult to store. To reduce losses and extend their uses, fresh SP could be converted into flour. SP cultivars with deep purple (Phichit 65-3) and orange-fleshed (T101) colors newly developed in Thailand were studied. The influence of drying methods on physico-chemical properties, anthocyanin, β-carotene and antioxidant activity retentions of purple and orange-fleshed SP flours (SPFs) was investigated. Peeled purple and orange SPs were pretreated by blanching (100 °C, 5 sec) and soaking in 0.5 % (w/v) sodium metabisulphite, then dried in either hot air oven at 50-80 °C or steamed for 10 min and placed to the drum dryer at 80-110 °C and 3-7 rpm drum speed. The drying processes significantly enhanced anthocyanin contents of SPFs by 1.8 to 3.8 times; however, there was a significant loss of β-carotene occurred during drying processes. Drum drying yielded SPFs with better color, higher total phenolic contents and antioxidant activity than the hot air drying. Pasting temperatures of hot air dried orange-fleshed SPFs (84-85 °C) were slightly higher than those of purple-fleshed SPFs (80-83 °C). Drum drying process produced pre-gelatinized (instant) SPFs as indicated by RVA and DSC results. The optimal conditions for drum dried and hot air dried SPF manufactured were 95 °C at 5 rpm and 70 °C, respectively, based on anthocyanin, β-carotene, total phenolic, antioxidant activity, color retentions, and pasting properties.

De novo sequencing and comprehensive analysis of the mutant transcriptome from purple sweet potato (Ipomoea batatas L.)

Purple sweet potatoes, rich in anthocyanin, have been widely favored in light of increasing awareness of health and food safety. In this study, a mutant of purple sweet potato (white peel and flesh) was used to study anthocyanin metabolism by high-throughput RNA sequencing and comparative analysis of the mutant and wild type transcriptomes. A total of 88,509 unigenes ranging from 200nt to 14,986nt with an average length of 849nt were obtained. Unigenes were assigned to Gene Ontology (GO), Clusters of Orthologous Group (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Functional enrichment using GO and KEGG annotations showed that 3828 of the differently expressed genes probably influenced many important biological and metabolic pathways, including anthocyanin biosynthesis. Most importantly, the structural and transcription factor genes that contribute to anthocyanin biosynthesis were downregulated in the mutant. The unigene dataset that was used to discover the anthocyanin candidate genes can serve as a comprehensive resource for molecular research in sweet potato.

The influences of purple sweet potato anthocyanin on the growth characteristics of human retinal pigment epithelial cells

Background

Anthocyanins have been proven to be beneficial to the eyes. However, information is scarce about the effects of purple sweet potato (Ipomoea batatas, L.) anthocyanin (PSPA), a class of anthocyanins derived from purple sweet potato roots, on visual health.

Objective

The aim of this study was to investigate whether PSPA could have influences on the growth characteristics (cellular morphology, survival, and proliferation) of human retinal pigment epithelial (RPE) cells, which perform essential functions for the visual process.

Methods

The RPE cell line D407 was used in the present study. The cytotoxicity of PSPA was assessed by MTT assay. Then, cellular morphology, viability, cell cycle, Ki67expression, and PI3K/MAPK activation of RPE cells treated with PSPA were determined.

Results

PSPA exhibited dose-dependent promotion of RPE cell proliferation at concentrations ranging from 10 to 1,000 µg/ml. RPE cells treated with PSPA demonstrated a predominantly polygonal morphology in a mosaic arrangement, and colony-like cells displayed numerous short apical microvilli and typical ultrastructure. PSPA treatment also resulted in a better platform growing status, statistically higher viability, an increase in the S-phase, and more Ki67+ cells. However, neither pAkt nor pERK were detected in either group.

Conclusions

We found that PSPA maintained high cell viability, boosted DNA synthesis, and preserved a high percentage of continuously cycling cells to promote cell survival and division without changing cell morphology. This paper lays the foundation for further research about the damage-protective activities of PSPA on RPE cells or human vision.

Flavonoids in Foods: A Review

The flavonoids in edible plants and foods are surveyed. The food materials rich in flavonoids, such as grape, tea, and cocoa receive particular attention. Also, the ingestion of flavonoids, the absorption and the bioavailability in vivo are discussed. Flavonoids have antioxidant and other living-body modulating activities. When expressing these functionalities, interactions between flavonoids and proteins are important. The interactions with various enzymes and receptors are described. Moreover, as an example of a processed food containing flavonoids, fermented red vinegar that we have investigated is highlighted. The structural determination, antioxidant activity and the generation mechanism of the new acylated polyphenols in red vinegar are described.

Absorption of Acylated Anthocyanins in Rats and Humans after Ingesting an Extract ofIpomoea batatasPurple Sweet Potato Tuber

We evaluated the absorbability of anthocyanins in humans and rats administered with a beverage prepared from an extract of the tuber of purple sweet potato (Ipomoea batatas Cultivar Ayamurasaki), or with an anthocyanin concentrate. Two major anthocyanin components, cyanidin 3-O-(2-O-(6-O-(E)-caffeoyl-beta-D-glucopyranosyl)-beta-D-glucopyranoside)-5-O-beta-D-glucopyranoside) and peonidin 3-O-(2-O-(6-O-(E)-caffeoyl-beta-D-glucopyranosyl)-beta-D-glucopyranoside)-5-O-beta-D-glucopyranoside), were detected in the plasma and urine of both rats and humans by HPLC or liquid chromatography/mass spectrometry (LC/MS). The plasma concentration of anthocyanins in humans reached a maximum 90 minutes after ingestion, and the recovery of anthocyanins in the urine was estimated as 0.01-0.03%. These results indicate that acylated anthocyanins could be selectively absorbed after ingesting food.

Determination of Acylated Anthocyanin in Human Urine after Ingesting a Purple-Fleshed Sweet Potato Beverage with Various Contents of Anthocyanin by LC-ESI-MS/MS

Eighty-seven healthy volunteers ingested a purple-fleshed sweet potato beverage with various contents of anthocyanin (beverage A; 22.1 mg/250 ml, B; 107.8, C; 84.9). An acylated anthocyanin, peonidin 3-caffeoylsophoroside-5-glucoside, was detected in the urine 2 h after ingestion. The concentrations were 15.1+/-2.2 microg/l of urine (mean+/-SEM), 46.6+/-5.3, and 53.3+/-2.2 for beverages A, B, and C respectively.

Purple sweet potato color ameliorates kidney damage via inhibiting oxidative stress mediated NLRP3 inflammasome activation in high fat diet mice

Inflammation plays a crucial role in the pathogenesis of obesity. Purple sweet potato color (PSPC) has potential anti-inflammation efficacy. We evaluated the effect of PSPC on kidney injury induced by high fat diet (HFD) and explored the mechanism underlying these effects. The results showed that PSPC (700 mg/kg per day) reduced body weight, ratio of urine albumin to creatinine, inflammatory cell infiltration, and Collagen IV accumulation in mice fed an HFD (60% fat food) for 20 weeks. PSPC significantly reduced the expression level of kidney NLRP3 inflammasome including NLRP3 and ASC and Caspase-1, and resulted in decline of IL-1β. Moreover, PSPC inhibited the activation of I kappa B kinase β (IKKβ) and the nuclear translocation of nuclear factor kappa beta (NF-κB). Additionally, PSPC decreased the expression level of oxidative stress-associated AGE receptor (RAGE) and thioredoxin interacting protein (TXNIP) in the upstream of NLRP3 inflammasome. These data imply that the beneficial effects of PSPC on HFD-induced kidney dysfunction and damage are mediated through NLRP3 signaling pathways, suggesting a potential target for the prevention of obesity.

In vivo antioxidant, hypoglycemic, and anti-tumor activities of anthocyanin extracts from purple sweet potato

Anthocyanin from purple sweet potato (PSP) extracted by microwave baking (MB) and acidified electrolyzed water (AEW) exhibited antioxidant activity. After further purification by macroporous AB-8 resin, the color value of PSP anthocyanin (PSPA) reached 30.15 with a total flavonoid concentration of 932.5 mg/g. The purified extracts had more potent antioxidant activities than the crude extracts. After continuously administering the PSP extracts to 12-mo-old mice for 1 mo, the anti-aging index of the experimental group was not significantly different from that of 5-mo-old mice. To a certain degree, PSPA was also effective for controlling plasma glucose levels in male Streptozocin (STZ)-treated diabetic mice. In addition, the extracts inhibited Sarcoma S180 cell growth in ICR mice. Mice consuming the PSP extracts formed significantly fewer and smaller sarcomas than mice consuming the control diets. The highest inhibition rate was 69.03%. These results suggest that anthocyanin extracts from PSP not only exert strong antioxidant effects in vitro, but also had anti-aging, anti-hyperglycemic, and anti-tumor activities.

Purple sweet potato color attenuates hepatic insulin resistance via blocking oxidative stress and endoplasmic reticulum stress in high-fat-diet-treated mice

Purple sweet potato color (PSPC), a class of naturally occurring anthocyanins, has been reported to possess a variety of health-promoting properties. Emerging evidence indicates that PSPC can suppress postprandial hyperglycemia via inhibition of α-glucosidases. However, the protective effects of PSPC on hepatic insulin resistance and the precise mechanisms underlying these protective effects have never been investigated. In this study, our data showed that PSPC effectively improved the fasting blood glucose level, glucose and insulin tolerance by suppressing reactive oxygen species (ROS) production and by restoring glutathione (GSH) content and antioxidant enzymes' activities. PSPC further prevented the oxidative-stress-mediated endoplasmic reticulum (ER) stress in the livers of high-fat-diet (HFD)-treated mice. Moreover, PSPC dramatically suppressed the c-Jun-N-terminal kinase 1 and I kappa B kinase β activation and nuclear factor-kappa B p65 nuclear translocation caused by oxidative and ER stress in the livers of HFD-treated mice. Ultimately, PSPC notably restored the impairment of the insulin receptor substrate-1/phosphoinositide 3 kinase/protein kinase B (Akt) insulin signaling in the livers of HFD-treated mice. In conclusion, our findings indicate that PSPC protected against HFD-induced hepatic insulin resistance via decreasing ROS level and blocking ROS-mediated ER stress.

Purple sweet potato color attenuates domoic acid-induced cognitive deficits by promoting estrogen receptor-α-mediated mitochondrial biogenesis signaling in mice

Recent findings suggest that endoplasmic reticulum stress may be involved in the pathogenesis of domoic acid-induced neurodegeneration. Purple sweet potato color, a class of naturally occurring anthocyanins, has beneficial health and biological effects. Recent studies have also shown that anthocyanins have estrogenic activity and can enhance estrogen receptor-α expression. In this study, we evaluated the effect of purple sweet potato color on cognitive deficits induced by hippocampal mitochondrial dysfunction in domoic acid-treated mice and explored the potential mechanisms underlying this effect. Our results showed that the oral administration of purple sweet potato color to domoic acid-treated mice significantly improved their behavioral performance in a step-through passive avoidance task and a Morris water maze task. These improvements were mediated, at least in part, by a stimulation of estrogen receptor-α-mediated mitochondrial biogenesis signaling and by decreases in the expression of p47phox and gp91phox. Decreases in reactive oxygen species and protein carbonylation were also observed, along with a blockade of the endoplasmic reticulum stress pathway. Furthermore, purple sweet potato color significantly suppressed endoplasmic reticulum stress-induced apoptosis, which prevented neuron loss and restored the expression of memory-related proteins. However, knockdown of estrogen receptor-α using short hairpin RNA only partially blocked the neuroprotective effects of purple sweet potato color in the hippocampus of mice cotreated with purple sweet potato color and domoic acid, indicating that purple sweet potato color acts through multiple pathways. These results suggest that purple sweet potato color could be a possible candidate for the prevention and treatment of cognitive deficits in excitotoxic and other brain disorders.

Polyphenol fatty acid esters as serine protease inhibitors: a quantum-chemical QSAR analysis

We investigated the ability of polyphenol fatty acid esters to inhibit the activity of serine proteases trypsin, thrombin, elastase and urokinase. Potent protease inhibition in micromolar range was displayed by rutin and rutin derivatives esterified with medium and long chain, mono- and polyunsaturated fatty acids (1e-m), followed by phloridzin and esculin esters with medium and long fatty acid chain length (2a-d, 3a-d), while unmodified compounds showed only little or no effect. QSAR study of the compounds tested provided the most significant parameters for individual inhibition activities, i.e. number of hydrogen bond donors for urokinase, molecular volume for thrombin, and solvation energy for elastase. According to the statistical analysis, the action of elastase inhibitors is opposed to those of urokinase and thrombin. Cluster analysis showed two groups of compounds: original polyphenols together with rutin esters with short fatty acid chain length and rutin esters with long fatty acid chain length.

Absorption of 6-O-caffeoylsophorose and its metabolites in Sprague-Dawley rats detected by electrochemical detector-high-performance liquid chromatography and electrospray ionization-time-of-flight-mass spectrometry methods

Absorption and metabolism of a natural compound, 6-O-caffeoylsophorose (CS) from acylated anthocyanins in a red vinegar fermented with purple sweet potato, were clarified. The absorption of CS and conjugated CS in blood from orally administrated Sprague-Dawley rats at a dose of 400 mg/kg was investigated by electrochemical detection-high performance liquid chromatography. As a result, CS was successfully detected in rat plasma (AUC(0-6h), 108.6 ± 8.1 nmol h/mL) and was found to be an intact absorbable polyphenol. In addition, half of the absorbed CS was detected as its conjugates (AUC(0-6h), 50.7 ± 5.7 nmol h/mL) as well as caffeic and ferulic acids from CS. By a time-of-flight-mass spectrometric analysis of CS-administered plasma sample, glucuronide and methylated conjugates of CS were identified, in addition to glucuronide, methylated, or sulfate conjugates of caffeic and ferulic acids. Consequently, CS was absorbed in intact form into rat blood and partly degraded to caffeic and ferulic acids or metabolized by glucuronidation, methylation, or sulfatation.

Molecular cloning and characterization of a flavonoid 3'-hydroxylase gene from purple-fleshed sweet potato (Ipomoea batatas)

Flavonoid 3'-hydroxylase (F3'H: EC 1.14.13.21) is an important enzyme which determines the hydroxylation pattern of anthocyanins. In this study, the full-length cDNA and genomic DNA of F3'H were isolated and characterized from the purple-fleshed sweet potato (Ipomoea batatas). IbF3''H was 1,789 bp containing a 1,554 bp open reading frame (ORF) encoding 518 amino acids. Comparative and bioinformatic analysis revealed that IbF3'H was highly homologous with F3'Hs from other plant species. Conserved domain search revealed that IbF3'H was a cytochrome P450 dependent enzyme. Three F3'H-specific motifs (V75VVAAS80, G427GEK430 and V433DVKG437) were conserved in IbF3'H. Phylogenetic analysis revealed that IbF3'H was clustered into the same subgroup with the homologues from I. purpurea, I. tricolor and I. nil. There were multiple copies of the IbF3'H gene in the genome of I. batatas. IbF3'H was constitutively expressed in all tested tissues including fibrous roots, thick roots, storage roots, stems and leaves. During storage root formation, IbF3'H was expressed most abundantly in the storage roots, suggesting that the anthocyanin biosynthesis is also active in the under-ground organs. IbF3'H expression was associated with anthocyanin accumulation in five different sweet potato cultivars tested. Complementative analysis implied that the full-length cDNA of IbF3'H could encode a functional protein and had a special catalytic activity of flavonoid 3'-hydroxylase.

Antioxidant potential of rat plasma by administration of freeze-dried jaboticaba peel (Myrciaria jaboticaba Vell Berg)

The effect of the intake of freeze-dried jaboticaba peel powder on the antioxidant potential of rats' blood plasma was investigated in two experiments. In the first, 35 male rats, divided into 5 groups, received 7 mg of anthocyanins/100 g of body weight, by gavage. The blood was withdrawn 0, 30, 60, and 120 min after gavage. The antioxidant capacity was evaluated in plasma by ORAC and TEAC. There was no significant difference in the plasmatic antioxidant potential among the groups. In the second experiment, 40 male rats were divided into 4 groups that consumed, respectively, 0, 1, 2, and 4% of freeze-dried jaboticaba peel powder added to their diet. An increase in the plasmatic antioxidant potential was observed for groups that received 1 and 2% of jaboticaba peel powder (1.7 times by TEAC method and 1.3 times by ORAC); however, the group that received 4% of the powder did not show antioxidant effects according to the methods used.

Anthocyanins isolated from the purple-fleshed sweet potato attenuate the proliferation of hepatic stellate cells by blocking the PDGF receptor

During the process of liver fibrosis, hepatic stellate cells (HSCs) play a critical role in the increased formation and reduced degradation of extracellular matrix in the liver. We investigated the anti-proliferative effects of an anthocyanin fraction (AF), isolated from the purple-fleshed sweet potato, on platelet-derived growth factor (PDGF)-BB-dependent signaling pathways in HSC-T6 cells. HSC proliferation plays a pivotal role in liver fibrogenesis. The AF suppressed HSC activation, including PDGF-induced proliferation and α-smooth muscle actin (α-SMA) expression. Additionally, AF inhibited PDGF-BB-induced Akt and ERK1/2 phosphorylation. AF inhibited the phosphorylation level of PDGF receptor-β (PDGFR-β) following PDGF-BB stimulation, providing a mechanism for the inhibition of AF-mediated kinase. These results suggest that AF suppresses HSC proliferation by blocking PDGFR-β signaling, inhibiting Akt and ERK1/2 activation and α-SMA expression.