Impact of flavonol extracts derived from green tea or targeted flavonols as secondary ingredients on intestinal glucose transport.

The purpose of the current study was to examine the effect of adding secondary ingredients such as green tea derived water-soluble polysaccharides (GTP) and flavonol aglycone rich fractions derived from cellulase treated green tea extract (FVN) into catechin rich green tea extracts (GTE) on wheat starch digestion and intestinal glucose transport using in vitro digestion with Caco-2 cells. Co-digestion of wheat starch with GTE (16.88 g L-1) or GTE + GTP + FVN (16.69 g L-1) appeared to promote starch hydrolysis compared to control (15.49 g L-1). In case of major flavonoids, addition of epigallocatechin gallate (EGCG), EGCG + myricetin (M) into wheat starch significantly increased the digestion of starch into glucose. Glucose transport rate decreased by 22.35% in wheat starch + GTE + GTP + FVN (1.39%), while the least amount of glucose (1.70%) was transported in EGCG mixed with M (1% of EGCG) as secondary ingredients among individual flavonoids formulation. It indicated that inhibitory effect on glucose transport was higher in addition of GTE, GTP, and FVN as excipients ingredients rather than targeted major flavonoids. Results from the current study suggest that whole green tea including flavonoid rich fractions could enhance hypoglycemic potential of GTE. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13197-021-05140-2.

Stability of Enzyme-Modified Flavonoid C- and O-Glycosides from Common Buckwheat Sprout Extracts during In Vitro Digestion and Colonic Fermentation.

Common buckwheat sprout (CBS) contains more flavone C-glycosides (FCGs) and flavonol O-glycosides (FOGs) than does common buckwheat seed. Both flavonoids in CBS are well known for providing benefits to human health. However, they are relatively less bioaccessible and more directly degradable to aglycone during digestion than are multiglycosylated flavonoids. To overcome such limitations, the water solubility and digestion stability of FCGs and FOGs were enhanced by transglycosylation using cyclodextrin glycosyltransferase. Gastric conditions had little effect on the stability of FCGs and FOGs and their enzyme-modified compounds. In contrast, under intestinal conditions, transglycosylated FCGs lost a glucose moiety and reverted to their parent compounds before transglycosylation. Under colonic fermentation using human fecal samples, the different profiles and concentrations of short-chain fatty acids were suggested to be mainly due to the presence of transglycosylated FCGs and FOGs. These findings indicate that the process of transglycosylation changes the bioaccessibility of flavonoids in CBS.

Profiling of In Vitro Bioaccessibility and Intestinal Uptake of Flavonoids after Consumption of Commonly Available Green Tea Types.

The aim of this study was to profile the bioaccessibility and intestinal absorption of epicatechins and flavonols in different forms of green tea and its formulation: loose leaf tea, powdered tea, 35% catechins containing GTE, and GTE formulated with green tea-derived polysaccharide and flavonols (CATEPLUS™). The bioaccessibillity and intestinal absorption of epicatechins and flavonols was investigated by using an in vitro digestion model system with Caco-2 cells. The bioaccessibility of total epicatechins in loose leaf tea, powdered tea, GTE, and CATEPLUS™ was 1.27%, 2.30%, 22.05%, and 18.72%, respectively, showing that GTE and CATEPLUS™ had significantly higher bioaccessibility than powdered tea and loose leaf tea. None of the flavonols were detected in powdered tea and loose leaf tea, but the bioaccessibility of the total flavonols in GTE and CATEPLUS™ was 85.74% and 66.98%, respectively. The highest intestinal absorption of epicatechins was found in CATEPLUS™ (171.39 ± 5.39 ng/mg protein) followed by GTE (57.38 ± 9.31), powdered tea (3.60 ± 0.67), and loose leaf tea (2.94 ± 1.03). The results from the study suggest that formulating green tea extracts rich in catechins with second components obtained from green tea processing could enhance the bioavailability of epicatechins.

Addition of flavonols and polysaccharides as excipient ingredients into epicatechin rich green tea extract inhibited free radical formation and glucose uptake.

It was revealed that excipient ingredients such as flavonols (FVN) or polysaccharides (GTP) which could be derived from green tea enhanced catechin absorption. We hypothesized that the addition of FVN or GTP as excipient ingredients into epicatechin rich green tea extracts (GTE) may improve the health benefits that accompany its consumption. When FVN8.7 (8.7% of GTE, w/w) was added to the GTE (20 mg) as an excipient ingredient, the bioaccessibility and intestinal absorption of total epicatechins was 1.2 and 1.5 times higher than that of only GTE, respectively. This was due to the free radical scavenging capacity of flavonols, showing 114.23 ± 3.07 µmol TE per g for GTE 100 + FVN8.7 and 113.64 ± 1.61 µmol TE per g for GTE 100 + FVN2, respectively. This was significantly higher than the GTE or GTE 100 + OW2 (onion peel and whangchil extracts, 2% of GTE, w/w) which have the same amount of total flavonols. Regarding potential hypoglycemic effects, co-digestion of GTE (20 mg) + green tea polysaccharides (2 mg) + FVN (5 mg) with wheat starch significantly reduced glucose intestinal absorption by 41.85 ± 1.75% compared to only the wheat starch. The results from the current study suggest that whole green tea components rich in flavonols and polysaccharides could be potential hypoglycemic excipient ingredients for green tea catechins.

pH-adjusted solvent extraction and reversed-phase HPLC quantification of isoflavones from soybean (Glycine max (L.) Merr.).

Soybeans, Glycine max (L.) Merr., are among the most important food crops worldwide. Isoflavones are major bioactive phytochemicals in soybeans, and have a variety of health benefits, including antioxidative, antiatherosclerotic, antiinflammatory, and weak estrogen-like effects. The isoflavone content and composition of soybeans vary according to the cultivar and the extraction solvent conditions. Therefore, we investigated the effects of three different solvent pHs (1.0, 5.5, and 10.0) on the isoflavone, total phenolic, and total flavonoid contents and antioxidant capacities of eight soybean cultivars developed in Korea. Twelve isoflavones in soybeans were efficiently separated and identified on a reversed-phase high-performance liquid chromatography (HPLC) system. The percentage distribution of isoflavones measured by HPLC in the eight soybean cultivars at various extraction pHs decreased as follows: malonyl isoflavones (67.2% to 81.3%) > isoflavone glucosides (16.2% to 29.0%; as nonacylated form) > acetyl isoflavones (1.6% to 5.9%). The highest contents of isoflavone glucosides, malonyl derivatives, and acetyl derivatives were extracted at solvent pHs of 10.0, 1.0, and 5.5, respectively. The solvent extraction at pH 1.0 yielded a lower total isoflavone content than those at pHs 5.5 and 10.0. However, the highest total phenolic and flavonoid contents were extracted from soybeans at pH 1.0. Soybeans extracted at pH 10.0 displayed the highest antioxidant capacities in the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical assay. Taken together, these results suggest that proper solvent pH adjustment is needed to maximize the extraction of targeted forms of isoflavones from soybeans. PRACTICAL APPLICATION: Soybeans contain a variety of bioactive compounds, including isoflavones, which function as antioxidants and weak phytoestrogens. Chemical and instrumental analyses can facilitate the selection of soybean cultivars with high amounts of isoflavones for soybean breeding and isoflavone-enriched product development. Proper solvent pH adjustment allows for the efficient extraction of high amounts of targeted isoflavone subgroups (acetyl and malonyl forms) from soybeans for functional food products.

Enrichment of Polyglucosylated Isoflavones from Soybean Isoflavone Aglycones Using Optimized Amylosucrase Transglycosylation.

Isoflavones in soybeans are well-known phytoestrogens. Soy isoflavones present in conjugated forms are converted to aglycone forms during processing and storage. Isoflavone aglycones (IFAs) of soybeans in human diets have poor solubility in water, resulting in low bioavailability and bioactivity. Enzyme-mediated glycosylation is an efficient and environmentally friendly way to modify the physicochemical properties of soy IFAs. In this study, we determined the optimal reaction conditions for Deinococcus geothermalis amylosucrase-mediated α-1,4 glycosylation of IFA-rich soybean extract to improve the bioaccessibility of IFAs. The conversion yields of soy IFAs were in decreasing order as follows: genistein > daidzein > glycitein. An enzyme quantity of 5 U and donor:acceptor ratios of 1000:1 (glycitein) and 400:1 (daidzein and genistein) resulted in high conversion yield (average 95.7%). These optimal reaction conditions for transglycosylation can be used to obtain transglycosylated IFA-rich functional ingredients from soybeans.

Stability and Fermentability of Green Tea Flavonols in In-Vitro-Simulated Gastrointestinal Digestion and Human Fecal Fermentation.

Flavonols, the second most abundant flavonoids in green tea, exist mainly in the form of glycosides. Flavonols are known to have a variety of beneficial health effects; however, limited information is available on their fate in the digestive system. We investigated the digestive stability of flavonol aglycones and glycosides from green tea under simulated digestion and anaerobic human fecal fermentation. Green tea fractions rich in flavonol glycosides and aglycones, termed flavonol-glycoside-rich fraction (FLG) and flavonol-aglycone-rich fraction (FLA) hereafter, were obtained after treatment with cellulase and tannase, respectively. Kaempferol and its glycosides were found to be more stable in simulated gastric and intestinal fluids than the derivatives of quercetin and myricetin. Anaerobic human fecal fermentation with FLG and FLA increased the populations of Lactobacilli spp. and Bifidobacteria spp. and generated various organic acids, such as acetate, butyrate, propionate, and lactate, among which butyrate was produced in the highest amount. Our findings indicate that some stable polyphenols have higher bioaccessibilities in the gastrointestinal tract and that their health-modulating effects result from their interactions with microbes in the gut.

Impact of Bioconversion of Gallated Catechins and Flavonol Glycosides on Bioaccessibility and Intestinal Cellular Uptake of Catechins.

Two bioconversions were applied to green tea extracts (GTE) and flavonol glycoside rich fraction (FVNg) derived from insoluble green tea extract by tannase and cellulase treatment in order to obtain gallated catechins (EnzGTE) and flavonol aglycone rich fraction (FVNa), respectively. The bioaccessibility of epicatechins from GTE increased with the addition of FVNg, FVNa, and flavonol aglycone rich fraction of commercial production (FVNap). Epigallocatechin-gallate (EGCG) and epicatechin-gallate (ECG) were highly recovered 4- and 125-fold, respectively, by adding FVNap. They were mostly affected by the radical scavenging activity provided from FVNap, showing remarkable 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (10769.3 µg/g) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) (8341.5 µg/g) values. The intestinal cellular uptake of epicatechins in GTE increased with the FVNap addition as follows: EGCG (332.46 ± 136.18%) > ECG (273.92 ± 97.92%) > epicatechin (EC) (150.22 ± 12.59%) > epigallocatechin (EGC) (131.21 ± 8.51%). EnzGTE and EnzGTE + FVNa were revealed to have a significant downregulation on the expression of P-glycoprotein (P-gp), up to 0.06- and 0.6-fold, respectively. The gene expression of multidrug resistance associated proteins 2 (MRP2) was reduced in EnzGTE + FVNap. The results suggest that coconsumption GTE or EnzGTE with GTE-derived flavonols could improve the bioavailability of epicatechins.

Protein Expression Level of Skin Wrinkle-Related Factors in Hairless Mice Fed Hyaluronic Acid.

The aim of this study was to evaluate the wrinkle improving effect of hyaluronic acid intakes. Wrinkles were induced by exposing the skin of hairless mice to ultraviolet B (UVB) irradiation for 14 weeks. Hyaluronic acid was administered to the mice for 14 weeks including 4 weeks before experiments. Skin tissue was assayed by enzyme-linked immunosorbent assay to determine protein expression of wrinkle-related markers. The group supplemented with high concentrations of hyaluronic acid appeared significantly better than control group for collagen, matrix metalloproteinase 1, interleukin (IL)-1ß, and IL-6 assay. Transforming growth factor-ß1 (TGF-ß1) and hyaluronic acid synthase 2 (HAS-2) were not shown to be significantly different. In conclusion, hyaluronic acid administration regulated expression levels of proteins associated with skin integrity, and improved the wrinkle level in skin subjected to UVB irradiation.

Treatment of Atopic Dermatitis Associated with Malassezia sympodialis by Green Tea Extracts Bath Therapy: A Pilot Study.

Multiple treatment modalities, including topical and systemic corticosteroid and phototherapy, have been used in treatment of patients with atopic dermatitis. However, long-term corticosteroid therapy may have various adverse effects. The purpose of this study was to investigate the therapeutic efficacy and safety of bath therapy using green tea extracts for treatment of patients with atopic dermatitis. A total of four patients with atopic dermatitis were enrolled in this study. A Malassezia multiplex detection kit was used in performance of multiplex PCR on clinical isolates, which confirmed Malassezia sympodialis. Subjects underwent treatment with bath therapy using green tea extracts three times per wk for a period of 4 wk. Assessment using the scoring atopic dermatitis (SCORAD) index, the visual analogue scale for pruritus, and transepidermal water loss was performed weekly. Laboratory tests were performed before and after treatment. All patients showed marked improvement on the mean SCORAD and visual analogue scale, and a significant decrease in the mean values of serum eosinophil counts was observed after treatment. Bath therapy with green tea extract is an effective, safe, and nonsteroidal therapy for treatment of patients with atopic dermatitis associated with Malassezia sympodialis.