食品中常用防腐剂和甜味剂的高效液相色谱同时测定法

目的建立食品中苯甲酸、山梨酸、糖精钠、乙酰磺胺酸钾、阿斯巴甜5种食品添加剂的高效液相色谱同时测定方法。方法采用ODS色谱柱,甲醇+0.02mol/L,乙酸铵(pH=6)(10+90)为流动相,流速1.0ml/min,二极管阵列检测器,阿斯巴甜检测波长214nm,其他均为228nm。根据保留时间、光谱图定性,峰高或峰面积定量。结果该方法5种添加剂在20～500μg/ml浓度范围内线性良好,相关系数达到0.99992～0.99999。相对标准偏差为1.6%～3.5%,回收率为92.1%～105.7%。苯甲酸、山梨酸、糖精钠、乙酰磺胺酸钾、阿斯巴甜的最低检出限依次为2.3、2.0、4.1、2.1、10.5mg/kg。结论该方法简便快速,准确可靠,可用于各类食品中苯甲酸、山梨酸、糖精钠、乙酰磺胺酸钾、阿斯巴甜含量的同时测定。     

甜味素对复合法制备大鼠肝硬化模型的影响

肝硬化动物模型是肝硬化的研究基础,研究肝硬化的发生机制及其防治必须建立良好的动物模型.目前,国内外制备肝硬化模型方法虽较多,但死亡率较高,成模率较低.本研究对目前最常用的复合法制备肝硬化模型的方法进行了改良,提高了肝硬化成模率、降低了大鼠死亡率.     

Antihyperglycemic and hepatoprotective properties of miracle fruit (Synsepalum dulcificum) compared to aspartame in alloxan-induced diabetic mice

ObjectiveThis study was undertaken to investigate the antihyperglycemic potential of miracle fruit (MF) as well as its hepatic safety as compared to aspartame in alloxan-induced diabetic mice.MethodsMF extracts were prepared and screened for their phytochemical composition using high-performance liquid chromatography (HPLC). Total phenolic, flavonoid and tannin contents and antioxidant potential were also determined. Additionally, MF was evaluated for its sensory attributes. For in vivo work, MF ethanol extract at high (MFH: 500 mg/kg body weight [BW]) and low (MFL: 250 mg/kg BW) doses as well as aspartame were injected intraperitoneally into alloxan-induced diabetic mice. Blood glucose levels were determined following acute and subchronic treatment. At the end of the study, animals were sacrificed, serum was collected for biochemical analysis and liver tissues were obtained for histopathological examination.ResultsMF ethanol extract contained more flavonoids and tannins, and had higher 1,1-diphenyl-1-picrylhydrazyl radical-scavenging activity (79.61%) compared to MF aqueous extract (P < 0.05). HPLC analysis of MF ethanol extract also revealed the presence of 10 antioxidants with quercetin comprising the major polyphenol. Additionally, sensory analysis of MF showed that its intake is effective in masking undesirable sourness. Subchronic administration of MFH proved amelioration of hyperglycemia in mice as compared to aspartame. Moreover, aspartame treatment significantly elevated (P < 0.05) the level of alanine aminotransferase and had destructive effects on the liver histopathology; however, hepatic architecture was restored by low and high doses of MF.ConclusionMF is an effective antihyperglycemic with hepatoprotective properties that can be used as a healthier alternative sweetening agent in place of aspartame for sour beverages.     

Serum biochemical responses under oxidative stress of aspartame in wistar albino rats

ObjectiveTo study whether the oral administration of aspartame (40 mg/kg body weight) for 15 d, 30 d and 90 d have any effect on marker enzymes, some selective liver and kidney function parameter, lipid peroxidation and antioxidant status in serum. To mimic human methanol metabolism, folate deficient animals were used.MethodAnimal weight, complete hemogram, marker enzyme in serum, some selected serum profile reflect liver and kidney function, plasma corticosterone level, and in serum, lipid peroxidation, nitric oxide, enzymatic and non-enzymatic antioxidant level was measured .ResultAfter 15 d of aspartame administration animals showed a significant change in marker enzymes, and antioxidant level. However, after repeated long term administration (30 d and 90 d) showed a significant change in some selected serum profile reflects liver and kidney function, along with marker enzymes, and antioxidant level.ConclusionsThis study concludes that oral administration of aspartame (40 mg/kg body weight) causes oxidative stress in Wistar albino rats by altering their oxidant/antioxidant balance.     

Oxidative stress evoked damages leading to attenuated memory and inhibition of NMDAR–CaMKII–ERK/CREB signalling on consumption of aspartame in rat model

Many controversial reports are available on the use of aspartame as it releases methanol as one of its metabolite during metabolism. The present study proposes to investigate whether long term (90 days) aspartame (40 mg/kg b.wt) administration could induce oxidative stress and alter the memory in Wistar strain male albino rats. To mimic the human methanol metabolism, methotrexate (MTX)-treated rats were included as a model to study the effects of aspartame. Wistar strain albino rats were administered with aspartame (40 mg/kg b.wt) orally and studied along with controls and MTX-treated controls. Aspartame interfered in the body weight and corticosterone levels in the rats. A marked increase in the mRNA and protein expression of neuronal nitric oxide synthase (nNOS) and induced nitric oxide synthase (iNOS) which resulted in the increased nitric oxide radical's level indicating that aspartame is a stressor. These reactive nitrogen species could be responsible for the altered cell membrane integrity and even cause death of neurons by necrosis or apoptosis. The animals showed a marked decrease in learning, spatial working and spatial recognition memory deficit in the Morris water maze and Y-maze performance task which could have resulted due to reduced hippocampal acetylcholine esterase (AChE) activity. The animal brain homogenate also revealed the decrease in the phosphorylation of NMDAR1–CaMKII–ERK/CREB signalling pathway, which well documents the inhibition of phosphorylation leads to the excitotoxicity of the neurons and memory decline. This effect may be due to methanol which may also activate the NOS levels, microglia and astrocytes, inducing neurodegeneration in brain. Neuronal shrinkage of hippocampal layer due to degeneration of pyramidal cells revealed the abnormal neuronal morphology of pyramidal cell layers in the aspartame treated animals. These findings demonstrate that aspartame metabolites could be a contributing factor for the development of oxidative stress in the brain.     

Effects of oral aspartame on plasma phenylalanine in humans and experimental rodents

Summary All aspartame does given to humans cause greater elevations in plasma (and, presumably, brain) phenylalanine than in plasma tyrosine. In contrast, doses of aspartame usually used in experiments on rodents preferentially elevate tyrosine. Since phenylalanine can inhibit brain catecholamine synthesis while tyrosine is the antidote for this effect, we determined the aspartame dose that would be needed to elevate phenylalanine more than tyrosine in rodents, using published data. In general rodents need 60 times as much aspartame, on a mg/kg basis, as humans to obtain comparable elevations in phenylalanine with respect to tyrosine.     

天冬甜素的化学合成法研究

甜味剂天冬甜素的合成方法主要有化学合成和酸法合成两大类．本文对化学合成法中五种具有代表性的合成方法进行了实验探讨，并对以不同原料进行缩合反应中间体及最终产物的产率作了研究比较。     

The effect of glucose administration on the recollection and familiarity components of recognition memory

Previous research has demonstrated that glucose administration facilitates long-term memory performance. The aim of the present research was to evaluate the effect of glucose administration on different components of long-term recognition memory. Fifty-six healthy young individuals received (a) a drink containing 25 g of glucose or (b) an inert placebo drink. Recollection and familiarity components of recognition memory were measured using the 'remember-know' paradigm. The results revealed that glucose administration led to significantly increased proportion of recognition responses based on recollection, but had no effect on the proportion of recognition responses made through participants' detection of stimulus familiarity. Consequently, the data suggest that glucose administration appears to facilitate recognition memory that is accompanied by recollection of contextual details and episodic richness. The findings also suggest that memory tasks that result in high levels of hippocampal activity may be more likely to be enhanced by glucose administration than tasks that are less reliant on medial temporal lobe structures.     

Reduction of the ochratoxin A-induced cytotoxicity in Vero cells by aspartame

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus ochraceus as well as other moulds. This mycotoxin contaminates animal feed and human food and is nephrotoxic for all animal species studied so far. OTA is immunosuppressive, genotoxic, teratogenic and carcinogenic. Recently lipid peroxidation induced by OTA has been reported. OTA, a structural analogue of phenylalanine, inhibits protein synthesis by competition with phenylalanine in the phenylalanine-tRNA aminoacylation reaction, constituting the main mechanism of OTA-induced cytotoxicity. Since it seems impossible to avoid contamination of foodstuffs by toxigenic fungi, investigation is required for preventing the toxicity of OTA. An attempt to prevent its toxic effect, mainly the inhibition of protein synthesis, has been made using aspartame (l-aspartyl-l-phenylalanine methyl ester) a structural analogue of both OTA and phenylalanine. Protein synthesis was assayed in monkey kidney cells (Vero cells) treated by increasing concentrations of OTA (10–100 μM). After 24 h incubation, protein synthesis was inhibited by OTA in a concentration dependent manner (the 50% inhibitory concentration, IC₅₀, was c.␣14.5 μM). Aspartame (A₁₉), at tenfold higher concentrations than OTA (100–1000 μM), was found to partially protect against the OTA-induced inhibition of protein synthesis in Vero cells, and more efficiently when added 24 h prior to the toxin (IC₅₀ 34 μM) than together (IC₅₀ 22 μM). As expected A₁₉(250 μM) prevented the OTA-induced leakage of certain enzymes, including lactate dehydrogenase, γ-glutamyl transferase, alkaline phosphatase, into the culture medium, and the concomitant decrease of their intracellular activity in OTA (25 μM)-treated cells. In order to investigate the effect of aspartame (A₁₉) on OTA-protein binding as explanation of the above results, the mycotoxin time- and concentration-dependent binding to human samples was studied in static diffusion cells with two compartments separated by a dialysis membrane. When A₁₉ (34 μM) was added to the upper compartment containing plasma before installing OTA (50, 250, 1240 μM) in the lower one, OTA binding was largely prevented (95–98%). When A19 (34 μM) was added to the lower compartment simultaneously with the toxin (50, 250, 1240 μM), for the lowest concentration of OTA, the same efficiency was shown in preventing OTA binding, but at the two high concentrations A₁₉ seemed less efficient. Received: 9 July 1996 / Accepted: 1 October 1996     

用木瓜蛋白酶在两相系统中合成二肽甜味剂Aspartame

研究了多种因素对木瓜蛋白酶在水－有机溶剂两相反应体系中合成二肽甜味剂Ａｓｐａｒｔａｍｅ能力的影响，结果表明，在本实验条件下，水与乙酸乙酯的比例为６：１００～７：１００之间为宜；反应最适ｐＨ为５．２；最适温度３７℃；反应时间为９ｈ；酶用量为１００～１２０ｍｇ／ｍｍｏｌ底物；Ｌ－ＰｈｅＯＭｅ与ＣＢＺ－Ｌ－Ａｓｐ的摩尔比为１：１。