Phytochemical Composition, Antiglycation, Antioxidant Activity and Methylglyoxal-Trapping Action of Brassica Vegetables.

Brassica vegetables are common in cuisines worldwide. The aim of this study was to investigate the antiglycation, methylglyoxal (MG)-trapping action and antioxidant activity of Brassica vegetable extract (BVE) from cabbage, cauliflower and Chinese cabbage. The results showed that cauliflower had the highest phenolic content with the strongest DPPH radical scavenging activity, ferric reducing antioxidant power and oxygen radical absorbance capacity. Seven phenolic acids and three flavonoids were identified by ESI-Q-TOF-MS analysis. The common phenolic compounds in all BVE were sinapic acid and p-hydroxybenzoic acid. The BVE (0.5 mg/mL) showed significant inhibitory activity against glucose-induced fluorescent advanced glycation end products (AGEs) formation (34 - 67%) and preserved the amount of protein thiol group (30 - 35%). In addition, all extracts (0.125 - 4 mg/mL) also had the ability to trap MG, a reactive glycating agent. Total phenolic content of BVE exhibited a positive correlation with DPPH radical scavenging activity (r = 0.524) and % inhibition of AGE formation (r = 0.570) and % MG-trapping capacity (r = 0.786). These findings suggest that the BVE possesses antioxidant and antiglycating activity that may help to protect against protein glycation and oxidation mediated by glycation reaction.

Anthocyanin-rich fraction from Thai berries interferes with the key steps of lipid digestion and cholesterol absorption.

Several studies have documented the hypolipidemic effect of anthocyanin-rich plants in vitro and in vivo. The objective of this study was to elucidate the inhibitory activity of anthocyanin-rich fraction from Thai berries against fat digestive enzymes. The ability of Thai berries to bind bile acid, disrupt cholesterol micellization and the cholesterol uptake into Caco-2 cells was also determined. The content of total phenolics, flavonoid and anthocyanin in Prunus domestica L. (TPE), Antidesma bunius (L.) Spreng, Syzygium cumini (L.) Skeels, and Syzygium nervosum A. Cunn. Ex DC was 222.7-283.5 mg gallic acid equivalents, 91.2-184.3 mg catechin equivalents, and 37.9-49.5 mg cyanidin-3-glucoside equivalents/g extract, respectively. The anthocyanin-rich fraction of all extracts inhibited pancreatic lipase and cholesterol esterase with the IC50 values of 90.6-181.7 µg/mL and 288.7-455.0 µg/mL, respectively. Additionally, all extracts could bind primary and secondary bile acids (16.4-36.6%) and reduce the solubility of cholesterol in artificial micelles (53.0-67.6%). Interestingly, TPE was the most potent extract on interfering the key steps of lipid digestion among the tested extracts. In addition, TPE (0.10-0.50 mg/mL) significantly reduced the cholesterol uptake into Caco-2 cells in a concentration-dependent manner. These results demonstrate a new insight into the role of anthocyanin-rich Thai berry extract on interfering the key steps of lipid digestion and absorption.

Effects of Different Cooking Methods and Palm Oil Addition on the Bioaccessibility of Beta-Carotene of Sweet Leaf (Sauropus androgynous).

Beta-carotene is one of phytochemicals which play role as natural antioxidant related to the reduction of oxidative stress that is linked to Non-communicable diseases (NCDs). Sweet leaf (Sauropus androgynous), one of the indigineous plants in Asia, contains high contents of beta-carotene. However, the bioaccessibility of beta-carotene in sweet leaf might be altered among the different cooking methods. Therefore, the effects of different cooking methods (raw, boiling, and microwave cooking) and addition of palm oil on the bioaccessibility of beta-carotene of sweet leaf were investigated before and during in vitro simulated gastrointestinal digestion. We found that the boiling and microwave cooking methods caused the lower beta-carotene contents in cooked sweet leaf compared to raw leaf. However, the addition of 10% (v/w) palm oil during cooking helped increasing the bioaccessible beta-carotene contents after digestion in all cooking methods, compared to those without palm oil addition (p<0.05). In addition, the bioaccessibility of beta-carotenes was found to increase about 20% when the palm oil was added into the microwaved sweet leaf. The findings of this study suggested that the addition of 10% (v/w) palm oil during cooking could improve the bioaccessible beta-carotene contents in the sweet leaf, especially when the sweet leaf was cooked by microwave.

Inhibitory Effect of Antidesma bunius Fruit Extract on Carbohydrate Digestive Enzymes Activity and Protein Glycation In Vitro.

Antidesma bunius (L.) spreng (Mamao) is widely distributed in Northeastern Thailand. Antidesma bunius has been reported to contain anthocyanins, which possess antioxidant and antihypertensive actions. However, the antidiabetic and antiglycation activity of Antidesma bunius fruit extract has not yet been reported. In this study, we investigated the inhibitory activity of anthocyanin-enriched fraction of Antidesma bunius fruit extract (ABE) against pancreatic α-amylase, intestinal α-glucosidase (maltase and sucrase), protein glycation, as well as antioxidant activity. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) chromatogram revealed that ABE contained phytochemical compounds such as cyanidin-3-glucoside, delphinidin-3-glucoside, ellagic acid, and myricetin-3-galactoside. ABE inhibited intestinal maltase and sucrase activity with the IC50 values of 0.76 ± 0.02 mg/mL and 1.33 ± 0.03 mg/mL, respectively. Furthermore, ABE (0.25 mg/mL) reduced the formation of fluorescent AGEs and the level of Nε-carboxymethyllysine (Nε-CML) in fructose and glucose-induced protein glycation during four weeks of incubation. During the glycation process, the protein carbonyl and ß-amyloid cross structure were decreased by ABE (0.25 mg/mL). In addition, ABE exhibited antioxidant activity through DPPH radical scavenging activity and Trolox equivalent antioxidant capacity (TEAC) with the IC50 values 15.84 ± 0.06 µg/mL and 166.1 ± 2.40 µg/mL, respectively. Meanwhile, ferric reducing antioxidant power (FRAP) showed an EC50 value of 182.22 ± 0.64 µg/mL. The findings suggest that ABE may be a promising agent for inhibiting carbohydrate digestive enzyme activity, reducing monosaccharide-induced protein glycation, and antioxidant activity.

The Effect of Isomaltulose Together with Green Tea on Glycemic Response and Antioxidant Capacity: A Single-Blind, Crossover Study in Healthy Subjects.

Isomaltulose, a naturally-occurring isomer of sucrose, is commonly used as an alternative sweetener in foods and beverages. The goal of this study was to determine the effect of isomaltulose together with green tea on postprandial plasma glucose and insulin concentration, as well as antioxidant capacity in healthy subjects. In a randomized, single-blind, crossover study, 15 healthy subjects (eight women and seven men; ages 23.5 ± 0.7 years; with body mass index of 22.6 ± 0.4 kg/m²) consumed five beverages: (1) 50 g sucrose in 400 mL water; (2) 50 g isomaltulose in 400 mL of water; (3) 400 mL of green tea; (4) 50 g sucrose in 400 mL of green tea; and (5) 50 g isomaltulose in 400 mL of green tea. Incremental area under postprandial plasma glucose, insulin, ferric reducing ability of plasma (FRAP) and malondialdehyde (MDA) concentration were determined during 120 min of administration. Following the consumption of isomaltulose, the incremental 2-h area under the curve (AUC0-2 h) indicated a higher reduction of postprandial glucose (43.4%) and insulin concentration (42.0%) than the consumption of sucrose. The addition of green tea to isomaltulose produced a greater suppression of postprandial plasma glucose (20.9%) and insulin concentration (37.7%). In accordance with antioxidant capacity, consumption of sucrose (40.0%) and isomaltulose (28.7%) caused the reduction of green tea-induced postprandial increases in FRAP. A reduction in postprandial MDA after drinking green tea was attenuated when consumed with sucrose (34.7%) and isomaltulose (17.2%). In conclusion, green tea could enhance the reduction of postprandial glucose and insulin concentration when consumed with isomaltulose. In comparison with sucrose, isomaltulose demonstrated less alteration of plasma antioxidant capacity after being consumed with green tea.

Moringa oleifera aqueous leaf extract inhibits reducing monosaccharide-induced protein glycation and oxidation of bovine serum albumin.

Advanced glycation end products (AGEs) play an important factor for pathophysiology of diabetes and its complications. Moringa oleifera is one of the medicinal plants that have anti-hyperglycemic activity. However, anti-glycation property of Moringa oleifera leaf extract on the different types of reducing monosaccharides-induced protein glycation has not been investigated. Therefore, the aim of this study was to examine the protective effect of Moringa oleifera aqueous leaf extract (MOE) on reducing sugars-induced protein glycation and protein oxidation. Total phenolic content of MOE was measured using the Folin-Ciocalteu method. Bovine serum albumin was incubated with 0.5 M of reducing sugars (glucose or fructose) with or without MOE (0.5-2.0 mg/mL) for 1, 2, 3 and 4 weeks. The results found that total phenolic content was 38.56 ± 1.50 mg gallic acid equivalents/g dry extract. The formation of fluorescent and non-fluorescent AGEs [N (ε)-(carboxymethyl) lysine (CML)] and the level of fructosamine were determined to indicate protein glycation, whereas the level of protein carbonyl content and thiol group were examined for protein oxidation. MOE (0.5-2.0 mg/mL) significantly inhibited the formation of fluorescent, N (ε)-CML and markedly decreased fructosamine level (P < 0.05). Moreover, MOE significantly prevented protein oxidation manifested by reducing protein carbonyl and the depletion of protein thiol in a dose-dependent manner (P < 0.05). Thus, the findings indicated that polyphenols containing in MOE have high potential for decreasing protein glycation and protein oxidation that may delay or prevent AGE-related diabetic complications.

Cultivar variations in antioxidant and antihyperlipidemic properties of pomelo pulp (Citrus grandis [L.] Osbeck) in Thailand.

Pomelo (Citrus grandis L. Osbeck) is a native fruit of great economic importance in Southeast Asia. To provide experimental evidence for the antioxidant and antihyperlipidemic properties of pomelo, 6 cultivars, including Kao-Yai (KY), Thong-dee (TD), Kao-Tangkwa (KT), Kao-Numpueng (KN), Ta-Koi (TK), and Tubtim Siam (TS) were evaluated. KY had the highest phenolic content, and the strongest 1,1-diphenyl-2-pireyhydrazyl radical scavenging capacity and hydroxyl radical scavenging activity. From the high-performance liquid chromatography analysis, naringin and naringenin were the major flavonoids in the KT and TK cultivars. Six pomelo cultivars had antihyperlipidemic activities including the inhibition of pancreatic lipase and cholesterol esterase, as well as cholesterol micelle formation and bile acid binding. Hierarchical clustering analysis showed that the 6 cultivars were separated into 2 classifications. In addition, the total phenolics of the pomelo cultivars were significantly correlated with ferric reducing antioxidant power and Trolox equivalent antioxidant capacity. The results suggest that pomelo provides significant health benefits and may be used for developing functional foods.

The protective effects of pomelo extract (Citrus grandis L. Osbeck) against fructose-mediated protein oxidation and glycation.

Chronic hyperglycemia induces non-enzymatic protein glycation, which plays an important role in the development of diabetic complications. Immense efforts have been made to determine effective antiglycation compounds from natural products. Pomelo has shown beneficial effects for human health. The objective of this study was to determine the antiglycation effect of pomelo extract against fructose-mediated protein oxidation and glycation. Our results showed that the pomelo extract (0.25 - 2.00 mg/mL) significantly inhibited the overall formation of advanced glycation end products (AGEs) in a concentration-dependent manner. The pomelo extract markedly decreased the level of fructosamine, which is directly associated with reduction in formation of AGEs and N (ε)-(carboxymethyl)lysine (CML). In addition, the pomelo extract inhibited protein oxidation through its ability to prevent the loss of thiol groups and reduced protein carbonyl formation. We characterized the active components in the pomelo extract by using high-performance liquid chromatography (HPLC), which showed that the pomelo extract contained naringin (11.90 ± 0.21 mg/g dried extract), hesperidin (12.04 ± 0.12 mg/g dried extract), neohesperidin (25.4 ± 0.12 mg/g dried extract), and naringenin (9.20 ± 0.19 mg/g dried extract). Our findings could provide a new insight into the antiglycation properties of the extract of the naturally occurring fruit pomelo for preventing AGE-mediated diabetic complications.

Cholesterol-lowering activity of the major polyphenols in grape seed.

The major polyphenols in grape seed have been shown to have beneficial health effects in the prevention of dyslipidemia and cardiovascular diseases. In this present study, we investigated the cholesterol-lowering activity of three major polyphenolic compounds found in grape seed. The results showed that gallic acid, catechin, and epicatechin significantly inhibited pancreatic cholesterol esterase in a concentration-dependent manner. Moreover, they bound to taurocholic acid, taurodeoxycholic acid, and glycodeoxycholic acid at levels ranging from 38.6% to 28.2%. At the concentration of 0.2 mg/mL, gallic acid, catechin, and epicatechin reduced the formation of cholesterol micelles 27.26 ± 2.17%, 11.88 ± 0.75%, and 19.49 ± 3.71%, respectively. These findings clearly demonstrate that three major polyphenolic compounds present in a particular grape seed have cholesterol-lowering activity by inhibiting pancreatic cholesterol esterase, binding of bile acids, and reducing solubility of cholesterol in micelles which may result in delayed cholesterol absorption.