Advanced glycation end products inhibitors from Alpinia zerumbet rhizomes

Advanced glycation end products (AGEs) are major factors responsible for the complication of diabetes. The present study was carried out to investigate the inhibitory activities on fructosamine adduct and α-dicarbonyl formations by hexane extracts of various parts of Alpinia zerumbet. Furthermore, we isolated two previously known compounds, namely 5,6-dehydrokawain (DK) and dihydro-5,6-dehydrokawain (DDK). 8(17),12-Labdadiene-15,16-dial (labdadiene) was isolated for the first time from the rhizome of A. zerumbet. The results showed that labdadiene (IC₅₀ = 51.06 μg/mL) had similar activity to rutin and quercetin against fructosamine adduct. The inhibition of α-dicarbonyl compounds formation by labdadiene was significantly higher than that of DK and DDK. Our results indicate that labdadiene is a potent antiglycation agent which was found to inhibit AGEs formation in three different steps in the pathway. These data indicate that labdadiene could be used to prevent glycation-associated complications in diabetes.     

Protective activity of flavonoid and flavonoid glycosides against glucose-mediated protein damage

The pathogenesis of diabetic vascular complications involves the formation of advanced glycation end-products (AGEs). AGEs accumulate slowly in the body with age and more rapidly in individuals with diabetes mellitus. An abnormally elevated blood glucose level in diabetes mellitus causes the formation of AGEs. Also, oxidative reactions contribute significantly to the formation of AGEs. The antioxidant flavonoids, quercetin, isoquercitrin, hyperin and cacticin from plants, decrease the formation of AGEs. This activity was examined using an in vitro glycation reaction. Of the tested compounds, isoquercitrin and hyperin showed a strong inhibitory activity against the formation of AGEs. These compounds showed inhibitory activities that were more potent than the positive control, aminoguanidine. These results suggest that isoquercitrin and hyperin may be promising agents to treat glycation-associated diseases.     

Evaluation of the in vitro inhibitory effects of buckwheat enhanced wheat bread extracts on the formation of advanced glycation end-products (AGEs)

In this study, the inhibitory effects of extracts from buckwheat enhanced wheat breads, on the formation of fluorescent advanced glycation end-products (AGEs) were studied in bovine serum albumin (BSA)/glucose and BSA/methylglyoxal (MGO) systems. Correlations with total phenolic compounds (TPC), total flavonoids (TF) as well as rutin (Ru) and quercetin (Q) contents were also identified.     

槲皮素与葛根素对食品体系中非酶糖基化的抑制作用

通过对果糖胺、二羰基化合物、5-羟甲基糠醛（5-hydroxymethylfurfural,5-HMF）和荧光性末端产物的检测,考察槲皮素和葛根素对食品体系非酶糖基化反应的抑制作用。结果表明：槲皮素能促进非酶糖基化早期产物果糖胺和5-HMF的生成,对反应中期的二羰基化合物和非酶糖基化末端产物（advanced glycation end products,AGEs）具有较强的抑制作用;葛根素能促进果糖胺的生成,抑制二羰基化合物的生成,对5-HMF和AGEs无影响。这可能与槲皮素与葛根素的结构差异有关。     

Preventive effects of guava (Psidium guajava L.) leaves and its active compounds against α-dicarbonyl compounds-induced blood coagulation

Diabetes is associated with a hypercoagulable state which may accelerate atherosclerosis, thrombosis and the diabetic microvascular complication. Endogenously produced α-dicarbonyl compounds are linked to the pathophysiology of diabetic complications. The effects of α-dicarbonyl compounds on coagulation parameters in vitro and the anticoagulant activities of aqueous extracts from guava leaves were examined. Incubation of plasma with glyoxal or methylglyoxal at 0.1 mM showed a significant decrease in thrombin clotting time (TT) (P < 0.05). However, they exhibited slight prolongation of the prothrombin time (PT) at 0.5 mM and no effect on the activated partial thromboplastin time (APTT). In order to define the action mechanism of the hypercoagulant activity, coagulation factors such as fibrinogen and antithrombin III activity were evaluated. The fibrinogen contents in plasma were decreased slightly with increasing concentrations of glyoxal and methylglyoxal. Moreover, methylglyoxal inhibited antithrombin III activity and over 80% of the activity was lost at 1.2 mM methylglyoxal. In contrast, guava leaf extracts exhibited significant inhibition of TT shortening induced by methylglyoxal. Guava leaf extracts and its active phenolic compounds including ferulic acid, gallic acid and quercetin also displayed a protective effect against methylglyoxal-induced loss of activity of antithrombin III. Thus, guava leaf extracts are a potent antiglycative agent and anticoagulant, which can be of great value in the preventive glycation-associated cardiovascular diseases in diabetes.     

Inhibitory effect of mung bean extract and its constituents vitexin and isovitexin on the formation of advanced glycation endproducts

The anti-glycation activity of four kinds of beans including mung bean, black bean, soybean and cowpea were evaluated. Aqueous alcohol extract of mung bean exhibited the strongest inhibitory activity against the formation of fluorescent advanced glycation endproducts (AGEs) in a bovine serum albumin (BSA)-glucose model, and the inhibitory activities of extracts of the four beans were found to be highly correlated with their total phenolic contents (R² = 0.95). Subsequent HPLC analysis of mung bean extract revealed two major phenolics which were purified and identified as vitexin and isovitexin by spectral methods. In the anti-glycation assays, both vitexin and isovitexin showed significant inhibitory activities against the formation of AGEs induced by glucose or methylglyoxal with efficacies of over 85% at 100 μM. In another assay, vitexin and isovitexin failed to directly trap reactive carbonyl species, such as methylglyoxal, suggesting that their anti-glycation activities may mainly be due to their free radical scavenging capacity.     

Antioxidation and antiglycation of 95% ethanolic extracts prepared from the leaves of black nightshade (Solanum nigrum)

Hyperglycemia results in the formation of advanced glycation end-products (AGE), resulting in an inflammatory response that induces insulin resistance. Evidence indicates that antioxidants can suppress the formation of reactive oxygen species, decrease levels of AGEs by inhibiting glycation. Black nightshade (Solanum nigrum) can be used as a medicinal food for improving blood glucose; however, the identities of the active compounds and how they counteract diabetes remain unknown. This study demonstrate that 95% ethanolic extracts of black nightshade exerted significant antioxidative activity compared with 50% ethanolic extracts and aqueous extracts. Moreover, 95% ethanolic extracts of black nightshade produced antiglycative activity, which contributed to the inhibition of fructosamine and generation of α-dicarbonyl compounds. The concentrations of solasonine and solamargine in the 95% ethanolic extracts were 0.484 and 0.183 mg/mg, respectively. These results suggest that black nightshade might serve as a novel source of functional ingredients that exert antiglycation and anti-diabetes activities.     

苹果多酚提取物对体外蛋白质非酶糖化的抑制作用

采用牛血清白蛋白-葡萄糖非酶糖化反应体系,研究苹果多酚提取物对体外蛋白质非酶糖化反应进程的影响。结果表明,苹果多酚提取物对蛋白质非酶糖化反应中间产物Amadori和高级糖化终末产物(AGEs)的形成均具有较强的抑制作用并呈明显的量效关系;在试验条件下,苹果多酚提取物对蛋白质非酶糖化反应中间产物Amadori和AGEs形成的最大抑制率分别可达80.85%和98.36%,IC50分别为0.40 g/L和0.28 g/L。说明苹果多酚提取物可能对糖尿病并发症具有一定的防治作用。     

槲皮素抑制蛋白糖基化及DNA损伤

建立牛血清白蛋白（bovine serum albumin,BSA）-还原糖、牛血清白蛋白-甲基乙二醛/乙二醛（bovineserum albumin-methylglyoxal/glyoxal,BSA-MGO/GO）反应体系,研究槲皮素对反应体系中晚期糖基化终产物（advanced glycation endproducts,AGEs）的抑制作用。考察了槲皮素在不同阶段对BSA-核糖体系中AGEs形成的抑制作用。并对槲皮素抑制二羰基化合物对质粒pBR322DNA的损伤进行研究。结果表明：槲皮素具有抑制BSA-还原糖、BSA-GO、BSA-MGO体系中AGEs形成的作用,达到显著抑制效果的浓度分别为1、0.25、0.25 mmol/L。槲皮素对BSA-MGO体系中AGEs产生的抑制作用强于BSA-GO体系。在BSA-核糖体系中,反应初期随着反应时间的延长抑制作用不断增大,12 d后,抑制作用趋于平缓,维持在60%左右。槲皮素对二羰基化合物对DNA的损伤有抑制作用,且与浓度成一定相关性。     

Antiatherogenic effect of guava leaf extracts inhibiting leucocyte-type 12-lipoxygenase activity

Oxidative modification of low density lipoprotein (LDL) is one of the critical steps for the development of atherosclerosis and leucocyte-type 12-lipoxygenase, highly expressed in macrophages, has been suggested to play an essential role in this process. In the present study, we show that guava leaf extracts inhibited, not only the leucocyte-type 12-lipoxygenase activity, but also LDL oxidation, mediated by the enzyme-overexpressing macrophage-like J774A.1 cells. Oral administration of guava leaf extracts to apoE-knockout mice at 100 mg of dry extracts/kg of body weight, once a day for 16 weeks, significantly reduced the area of atherogenic lesions developed in the aorta and aortic sinus. The major components inhibiting leucocyte-type 12-lipoxygenase contained in guava leaf extracts were identified as ethyl gallate and quercetin. The inhibitory effects of guava leaf extracts on the leucocyte-type 12-lipoxygenase activity, as well as on cell-mediated LDL oxidation, might be involved in the antiatherogenic effect of the extracts.     

Inhibitory effects of Lemon balm (Melissa officinalis, L.) extract on the formation of advanced glycation end products

Lemon balm (Melissa officinalis) is a medicinal herb possessing functional compounds with unexplored anti-glycative action. The anti-glycative activity of Lemon balm extract was evaluated in the bovine serum albumin (BSA)/glucose system. The level of glycation, conformational alterations and protein binding to RAGE receptors were assessed by specific fluorescence, Congo red binding assay, circular dichroism, ligand and Western blotting. Ethanol fractions of Melissa leaf exhibited the highest inhibitory effects on the formation of advanced glycation end products (AGEs) and the late stage of glycation process. Significant alteration in the secondary structure of albumin was observed upon glycation, which was mitigated by applying the herb extract. Moreover, upon treatment with balm extract, glycated albumin adopts a secondary structure impeding its detection by RAGE receptors of microglial cells. Our results represent the anti-glycative properties of Melissa extract and its application for possible treatment of AGE-associated diseases.     

Chemical composition and anti-proliferative and anti-inflammatory effects of the leaf and whole-plant samples of diploid and tetraploid Gynostemma pentaphyllum (Thunb.) Makino

Leaf and whole-plant samples of the diploid and tetraploid Gynostemma pentaphyllum (GP) were investigated and compared for their chemical compositions, and their potential anti-proliferative and anti-inflammatory effects. The highest levels of total flavonoids and phenolics were observed in the diploid leaf botanical (2L3) at 36.84 mg rutin equiv/g and 41.15 mg gallic acid equiv/g, respectively. The diploid leaf sample (2L2) had the highest amount of rutin and quercetin contents of 77.7 μmol quercetin equiv/g. The tetraploid whole-plant botanical (4L3) had the highest total saponin content of 227.1 mg gypenoside equiv/g. Extracts from all tested GP samples showed time- and dose-dependent antiproliferative effects in HT-29 cells, and the diploid leaf samples had the overall highest inhibitory activity. These extracts had different order of antiproliferative properties in the LNCaP cells, suggesting the potential selective inhibition of GP extracts against different types of cancer cells and the effect of the cell model in screening and evaluation of antiproliferative components. In addition, the diploid leaf extracts showed the strongest inhibitory effects on the expression of TNF-α, IL-6 and COX-2 mRNA at final concentrations of 0.2 and 1 mg botanical equiv/ml media. The results from this study will be used to develop new nutraceutical products from G. pentaphyllum.     

Inhibition of Fluorescent Advanced Glycation End-Products and N-Carboxymethyllysine Formation by Several Floral Herbal Infusions

The hyperglycemia-accelerated formation of advanced glycation end-products is involved in the pathogenesis of diabetic complications. The present study evaluated the antiglycation capacities of numerous flower herbal infusions, based on their capacity to inhibit the formation of fluorescent advanced glycation end-products and N-carboxymethyllysine in in vitro albumin/glucose and albumin/methylglyoxal systems. The antiglycation capacities of Sweet Osmanthus and Rose infusions were better than that of Chrysanthemum infusion, which is a well-documented antiglycation herb. Lavender and Chamomile infusions have an equivalent antiglycation capacity to that of Chrysanthemum, with a moderate effect. Moreover, the total phenolic content of a particular flower infusion was significantly correlated with its antiglycation capacity. This result indicated that phenolic compounds are responsible for the antiglycation activity of flower infusions.     

Inhibitory effect of polysaccharides from pumpkin on advanced glycation end-products formation and aldose reductase activity

Inhibitors of advanced glycation end-products formation and aldose reductase have been considered to be potential treatment of diabetic complications. This study investigated the abilities of polysaccharides extracted from pumpkin (PPs) to inhibit the formation of advanced glycation end-products and aldose reductase. The results showed that the inhibitory effects of PPs on the formation of advanced glycation end-products were higher than 50%, at 200 μg/ml, stronger than the positive control aminoguanidine, and the inhibitory effects of PPs on aldose reductase were higher than 58%, at 500 μg/ml, but not as potent as the positive control epalrestat. The result of this work suggests that pumpkin polysaccharides displayed therapeutic potential in the prevention and treatment of diabetic complications.     

Anti-AGE activity of poplar-type propolis: mechanism of action of main phenolic compounds

This study aimed to compare the protective effect of two geographically distinct propolis against the formation of advanced glycation end products (AGEs). The polyphenol content of propolis extracts (EEPs) was analysed using HPLC-DAD-MS profiling and evaluated for their protective effects against pentosidine-like AGEs. Dicarbonyl trapping capacities of major EEP compounds were determined using a methylglyoxal scavenging in vitro assay. Both propolis samples were characterised with high levels of pinobanksin derivatives exhibiting strong anti-AGE properties. EEPs reduced AGE formation more effectively than well-known natural AGE inhibitors such as quercetin or chlorogenic acid. Individual evaluations of the five major compounds in EEPs showed that flavonoids strongly inhibit the formation of AGEs by trapping dicarbonyl intermediates, whereas compounds such as caffeic acid derivatives only act as antioxidant agents. Propolis is thus a promising candidate for the prevention and control of AGE-related chronic diseases.     

大豆11S球蛋白糖基化有害交联产物的形成及抑制机理

目的：针对食品工业大豆蛋白糖基化改性工艺,建立大豆11S球蛋白-糖模拟体系,探究该体系中晚期糖基 化终产物（advanced glycation end products,AGEs）形成的影响因素,探究黄酮类化合物抑制AGEs形成的机理, 以便进行有效调控。方法：荧光光谱法（λex/λem＝340 nm/465 nm）测定糖的种类和浓度、温度、pH值以及黄酮抑制 剂等对AGEs形成的影响,十二烷基硫酸钠-聚丙烯酰胺凝胶电泳表征糖基化过程及黄酮对AGEs的抑制效果,通过 液相色谱-串联质谱（liquid chromatograph-tandem mass spectrometry,LC-MS/MS）测定反应过程中槲皮素及其产物 的变化。结果：糖种类为果糖;11S球蛋白与果糖质量浓度分别为2、8 mg/mL,pH值为9.2,温度为121 ℃条件下产 生的荧光性AGEs量最多;槲皮素、木犀草素、染料木素、芦丁4 种黄酮对荧光性AGEs的形成均有一定抑制效果; LC-MS/MS结果表明槲皮素通过捕获糖基化中间产物甲基乙二醛（methylglyoxal,MGO）,抑制了大分子交联性的 荧光性AGEs形成;十二烷基硫酸钠-聚丙烯酰胺凝胶电泳验证了1 mmol/L槲皮素有效降低了大分子交联的产物,但 不影响糖的修饰改性,乳化性能得到较好的改善。结论：采用分子质量较大的糖,降低糖质量浓度、pH值和反应 温度,添加黄酮类化合物可有效抑制大豆蛋白糖基化过程中有害产物AGEs的形成。     

Anti-glycation and inhibition of starch hydrolyzing enzymes by enzymatically hydrolysed djulis (Chenopodium formosanum Koidz.) hull,leaf and seedling

Glycation is the reaction of the carbonyl group of the reducing sugars to form advanced glycation end products (AGEs), which are major contributors to glycation-related diabetes. Hence, it is necessary to find an alternative approach in management of diabetes that can reduce the formation of AGEs. Therefore, we investigated the anti-glycation and starch hydrolysing enzymes inhibition by djulis (Chenopodium formosanum Koidz.) hull, leaf and seedling treated with enzymatic hydrolysis (EH) and studied the possible phenolic compounds responsible for the anti-glycation efficacy. Djulis samples treated with EH showed a high inhibitory effect on AGEs (65.04–72.77%), methylglyoxal (80.01–90.70%), α-amylase (86.37–93.50%) and α-glucosidase (35.50–38.16%). Bioactive compounds were significantly contributed to the anti-glycation potential of djulis samples. Therefore, djulis hull, leaf and seedling treated with EH could be used as a natural potential source in the prevention of glycation-associated diabetes, health risks and to increase food productivity.     

8种别样茶对AGEs抑制能力的筛选及其抑制机制探究

目的:本研究通过检测非酶糖基化终末产物（advanced glycation end-products,AGEs）生成量评价8种别样茶的糖基化抑制能力,并探究抑制效果较好的别样茶对AGEs生成各阶段的抑制作用机制。方法:本研究首先对8种别样茶水提液中总黄酮含量进行检测,接着通过构建体外蛋白质非酶糖基化模型实验检测了8种别样茶抑制AGEs生成的能力,最后择优测定其对糖基化早期产物果糖胺、中期产物活性羰基化合物以及蛋白质交联的抑制能力,从而探究其对非酶糖基化反应的抑制机制。结果:大叶苦丁茶（Ilex latifolia Thunb）和甜茶（Rubus suavissimus S. Lee）对AGEs的抑制效果在8种别样茶中较为突出,50 μg/mL时AGEs抑制率分别达到了76.31%±0.87%和81.75%±0.41%;大叶苦丁茶和甜茶主要通过抑制糖基化早期、中期产物的生成量来减少AGEs的产生。其中,500 μg/mL甜茶对果糖胺抑制率最高（59.12%）,蛋白质交联抑制率最高（81.41%）,5000 μg/mL大叶苦丁茶对活性羰基化合物抑制率最高（94.24%）。结论:大叶苦丁茶及甜茶可以作为抑制糖基化反应的功能食品,本研究可为具有抑制AGEs产生功效原料的综合开发利用提供一定的理论依据。     

Inhibition of the formation of advanced glycation end products by thymoquinone

The inhibitory activity of thymoquinone, a major quinone from black seeds (Nigella sativa) against the formation of advanced glycation end products was studied using the hemoglobin-δ-gluconolactone, human serum albumin–glucose, and the N-acetyl-glycyl-lysine methyl ester–ribose assays. A comparison was made with the inhibitory activity of aminoguanidine. The cytotoxicity of thymoquinone was studied by the release of lactate dehydrogenase from platelets and the levels of plasma thiols. At 20 μM, thymoquinone inhibited 39% of hemoglobin glycation, 82% of post-Amadori glycation products, reduced methyglyoxal-mediated human serum albumin glycation by 68%, inhibited 78% of late glycation end products. Aminoguanidine at 10 mM was less effective than thymoquinone. The IC₅₀ for thymoquinone and aminoguanidine were 7.2 μM and 1.25 mM, respectively. Thymoquinone at 20–50 μM was not toxic to platelet lactate dehydrogenase and plasma thiols. The potential of thymoquinone in food applications is discussed.