绿茶和腰果中的天然抗菌成分及其结构—活性关系研究

对茶叶、腰果风味成分中具有较强抗菌活性的醛类、醇类的量子化学进行了计算，并与相应的抗菌性能参数进行了相关分析。结果表明，在所有量子化学参数中，只有最低空轨道能量与最低抑菌浓度值的相关度相对较高。说明果蔬中具有抗菌活性的风味成分主要是作用于微生物细胞中的亲电反应体系。抗菌剂活性中心周围基团的空间位阻效应与ＭＩＣ值呈显著的负相关（Ｐ〈０．０２），表明抗菌活性中心与菌体系统的有效接触碰撞是影响抗菌性能的     

二元取代壳聚糖季铵盐的抗菌活性

对合成的系列单取代和双取代壳聚糖季铵盐进行了抗菌试验。实验结果表明，单取代壳聚糖季铵盐抗菌活性弱于双取代壳聚糖季铵。在双取代壳聚糖季铵盐中，O-季铵化-N-壳聚糖内桂醛席夫碱的最低抑菌浓度（MIC）最小，对金黄色葡萄球菌和大肠杆菌的MIC分别达到了为0．01％和0．02％。试验结果表明，壳聚糖衍生物抗菌活性与结构之间有一定的构效关系。     

丁烯二酸及其酯类抗菌作用和机理的研究

本文对丁烯二酸及其酯类的分子结构特点与抗菌活性之间的关系进行了研究．并采用氨基酸自动分析仪检测菌体蛋白质组成在加入丁烯二酸及其酯类后的变化情况，最后应用量子化学自治场理论中全略微分重叠计算法（简称CNDO法耐其量子化学特性进行了计算。结果表明．丁烯二酸及其酯类均表现出一定的抗菌活性，其大小与最低空轨道能量、β－碳原子的最低空轨道系数之间存在显著的直线关系，揭示其抗菌机理可能是抑制了菌体有关酶类正常的合成代谢。     

紫苏黄酮抗菌活性表征

该试验利用超声波辅助乙醇提取法对紫苏黄酮进行提取。分别以大肠杆菌、金黄色葡萄球菌、霉菌及酵母菌为供试菌,采用滤纸片法等研究方法,通过抑菌圈、最小抑菌浓度（minimum inhibitory concentration,MIC）、最低杀菌浓度（minimum bactericidal concentration,MBC）等指标测定,探究紫苏黄酮抗菌活性。在此基础上,进一步研究紫苏黄酮抗菌活性的pH值稳定性和热稳定性。结果表明,紫苏黄酮对这4种供试菌均有一定的抗菌效果,其对大肠杆菌的抗菌活性最强（MIC和MBC分别为0.625、1.3 mg/mL）,其次为金黄色葡萄球菌（MIC和MBC分别为1.25、2.5 mg/mL）,再次为酵母菌（MIC和MBC分别为2.5、4.8 mg/mL）和霉菌（MIC和MBC分别为2.5、5 mg/mL）。在pH值为3～7的范围内,提取液浓度在各菌的MIC浓度下,均能完全有效抑制4种微生物的生长。温度条件在100℃以下时,紫苏黄酮的抗菌能力不受影响,当温度上升至121℃及以上时,会对抗菌活性产生负面影响。     

菊花脑茎叶抗病原菌活性及其有效成分研究

首次以菊花脑提取物对大肠杆菌、金黄色葡萄球菌、枯草芽孢杆菌等6种常见的病原细菌及黑曲霉、啤酒酵母等4种病原真菌进行了拮抗试验,结果表明菊花脑提取物A、B和C具有较强的拮抗病原菌的活性,且抗菌活性有明显的量效关系,其对各种供试病原细菌的最低抑菌浓度为0.3%～0.5% (g/ml),对供试病原真菌的MIC值从0.3%～1.0%不等。菊花脑提取物A(挥发油)显示了广谱的抗菌范围,其对供试细菌和供试真菌的抑菌效力相当,但菊花脑提取物B和C(非挥发性成分)对供试细菌的拮抗作用(MIC值为0.3%～0.5%)远大于对供试真菌(MIC值为0.7%～1.0%)的作用。菊花脑中起抗菌作用的主要成分是挥发油、总黄酮、苦味素、野菊花内酯等活性成分。     

肉桂醛,酸类化合物抗菌活性的特征及其与化学结构关系的研究

本文对肉桂醛、酸及其衍生物的抑菌效果进行了测定，对其量子化学参数进行了计算，并对这类化合物抗菌活性分子化学结构之间的关系进行了相关分析。结果表明，该类化合物抑菌率ＥＦＰＯ、ＥＬＵＭＯ和ＥＨＯＭＤ的相关系数分别为－０．７８１４、０．７３２８和０．６３１８。该类化合物的抗菌活性中心原子可能是碳基氧、α－碳、β－碳，由这些原子组成的不饱和羰基共轭体系可能是抗菌剂的活性功能率。     

翠云草挥发油成分分析、抗氧化及抗菌效果

目的:对翠云草挥发油进行成分分析、抗氧化及抗菌研究。方法:采用气相色谱-质谱仪(GC-MS)对翠云草挥发油化学成分进行分离鉴定;采用DPPH法,FRAP法和金属离子螯合能力实验评价翠云草挥发油的体外抗氧化活性;用纸片扩散法测定翠云草挥发油的抗菌活性,包括3种革兰氏阳性菌,即金黄色葡萄球菌、粪肠球菌、化脓棒状杆菌,和3种革兰氏阴性菌,即大肠杆菌、铜绿假单胞菌、变形杆菌。结果:从翠云草中分离出52个峰,鉴定出50种成分,已鉴定成分占总面积的98.58%,主要成分有植酮(21.40%)、角鲨烯(8.53%)、棕榈酸(6.71%)、二十八烷(6.03%)等。翠云草具有潜在的抗氧化活性,DPPH自由基清除的IC₅₀值为0.76 mg/mL,铁离子还原能力的FRAP值为0.86 mmol/L,金属离子螯合作用的EC₅₀值为0.71 mg/mL。通过抗菌实验的MIC和MBC结果表明翠云草挥发油对粪肠球菌、化脓棒状杆菌、大肠杆菌和铜绿假单胞菌则具有较好的抗菌活性,其中对粪肠球菌的MIC值为5 μL/mL,MBC值为10 μL/mL;对化脓棒状杆菌的MIC值为10 μL/mL,MBC值为20 μL/mL。结论:本文通过GC-MS分析了翠云草挥发油成分,并首次发现其具有一定的抗氧化活性及抗菌活性。     

当归提取物的体外抗菌活性评价

目的：对当归进行体外抗菌活性评价,初步探讨其作用机制。方法：采用加热回流法制备当归提取物;用微量肉汤稀释法测定其抗菌活性（MIC）;用扫描电镜法观察用药前后测试菌的形态变化,用比色法测定用药后测试菌脱氢酶的活性变化。结果：鲜当归须状根、干燥当归身和尾的丙酮提取物具有抑制6种测试菌生长繁殖的活性,MIC分别为1．25、0．625和0．625g·L-1,鲜当归尾的丙酮提取物和干当归须状根的水提取物对部分测试菌具有抗菌作用,MIC均为1．25g·L-1扫描电镜结果显示,当归丙酮提取物处理后的金黄色葡萄球菌和大肠杆菌均出现细胞壁破裂和内容物外溢;另外,当归丙酮提取物对金黄色葡萄球菌和大肠杆菌脱氢酶的活性有影响,随着提取物浓度的提高,脱氢酶活性逐渐减弱。结论：当归的丙酮提取物对所选测试菌普遍具有抗菌活性,其抗菌机制可能与破坏细胞壁的完整性以及抑制脱氢酶活性有关。     

花生壳乙醇提取物(EEPH)抗菌性的研究

测定了花生壳乙醇提取物(EEPH)对食品中常见污染菌的抗菌活性，探讨了热处理和pH值对其抗菌活性的影响，阐明了花生壳乙醇提取物的抗菌特点以及作为食品天然防腐剂的开发价值。结果发明：花生壳乙醇提取物的抑菌作用显著，其抗菌活性随着其浓度增加而增强，对细菌和真菌的最低抑制浓度(MIC)分别为0．28‰和0．50‰；花生壳乙醇提取物的抗菌活性具有热稳定性，能忍受高温短时的热处理，并且在pH5～9的范围内均具有抗菌活性。     

通过搅拌吸附与溶媒萃取法测定啤酒的某些风味物质

本文主要论述啤酒中某些风味成分的测定方法。检测的啤酒风味成分主要有乙酸异戊酯、己酸乙酯、乙酸苯酯、癸酸乙酯、乙酸乙酯、苯乙酸乙酯、月桂酸乙酯、甘油酸乙酯、棕榈酸乙酯等。利用搅拌提取与溶媒萃取相结合的技术（SBSE），运用气相色谱离子火焰探测器对上述成分进行有效分析。本文的方法重现性好（相对标准偏差RSD2．1％～7．3％），在测定风味浓度范围内（如浓度0．015～30mg／L）都有比较好的线性相关性（关联系数的平方值远远高于0．9995），并与真实值比较吻合，即：可回收率为78％～107％，精确率高（RSD〈7．3％）。     

In vitro antimicrobial activities against cariogenic streptococci and their antioxidant capacities: A comparative study of green tea versus different herbs

The antimicrobial activity against cariogenic bacteria, total antioxidant capacity and phenolic constituents of methanolic extracts from 11 herbs were investigated and compared with those of green tea (Camellia sinensis). Among the 12 tested herbs, eight herbal extracts could inhibit the growth of Streptococcus sanguinis. Jasmine, jiaogulan, and lemongrass were the most potent, with minimum inhibitory concentrations (MIC) of 1 mg/ml, while green tea was less effective, with a MIC of 4 mg/ml. Among them, only rosemary could inhibit the growth of S. mutans at a MIC of 4 mg/ml. Total antioxidant capacities of herbal extracts were analyzed by three different assays, including 2,2-diphenyl-1-picrylhydrazyl (DPPH·) radical scavenging activity, trolox equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC). Regardless of the assays used, green tea exhibited the highest antioxidant capacity, followed by osmanthus. Wide variations in total phenolics and total flavonoids of herbal tea extracts were observed. Chlorogenic acid was detected in high amount in honeysuckle and duzhong. These data suggest that rosemary is a potent inhibitor of oral streptococci, and green tea and osmanthus may be effective potential sources of natural antioxidants.     

Comparison of the antioxidant capacity and the antimicrobial activity of black and green tea

Tea is a common beverage. The green tea is preferentially recommended for its strong antioxidant properties and also for its antimicrobial activity. The antioxidant capacities of 30 samples (black and green tea) were determined by the chemiluminescent Trolox equivalent antioxidant capacity (TEAC) determination. The average value of TEAC of the non-fermented (green tea) and semi-fermented tea samples was 1.43 mM and the average value of TEAC of the fermented teas (black tea) samples was 1.43 mM. All samples were stored in freezer (?20 °C) and the TEAC determination was repeated after a year. The average values of TEAC of non-fermented and semi-fermented tea samples were twofold lower in comparison to fermented tea samples and only 20% of average value of TEAC of the fresh tea infusion. The parallel determinations of minimal inhibitory concentration (MIC) on gram-positive and gram-negative bacterial strains (Enterococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli) were done. Also the MIC was possible to determine after a year. The assumed prevailing antioxidant and antimicrobial activities of non-fermented tea infusions were not confirmed as well as the dominant antioxidant and antimicrobial properties of specific type of tea infusion.     

二氢杨梅素抗氧化机制探讨

二氢杨梅素可开发利用价值极大,它的抗氧化活性更是研究的热点。本研究通过量子化学计算手段和实验醚化处理相结合,确定了二氢杨梅素分子结构的抗氧化活性中心在其B环上的3’、4’、5’位连酚羟基结构,同时也验证了量子化学计算在研究黄酮类物质分子结构与表现性质中的正确预测性和指导性。     

Antiproliferative activity of tea catechins associated with casein micelles,using HT29 colon cancer cells

Numerous studies have shown that green tea polyphenols display anticancer activities in many organ sites by using different experimental models in rodents and in cultured cell lines in vitro. The present study tested the ability of casein micelles to deliver biologically active concentrations of polyphenols to HT-29 colon cancer cells. Epigallocatechin gallate (EGCG), the major catechin found in green tea, was used as the model molecule, as it has been shown to have antiproliferative activity on colon cancer cells. In the present work, we hypothesized that due to the binding of caseins with EGCG, casein micelles may be an ideal platform for the delivery of this bioactive molecule and that the binding would not affect the bioaccessibility of EGCG. The cytotoxicity and proliferation behavior of HT-29 colon cancer cells when exposed to free EGCG was compared with that of nanoencapsulated EGCG in casein micelles of skim milk. Epigallocatechin gallate-casein complexes were able to decrease the proliferation of HT-29 cancer cells, demonstrating that bioavailability may not be reduced by the nanoencapsulation. As casein micelles may act as protective carriers for EGCG in foods, it was concluded that nanoencapsulation of tea catechins in casein micelles may not diminish their antiproliferative activity on colon cancer cells compared with free tea catechins.     

Green tea extract: possible mechanism and antibacterial activity on skin pathogens

Camellia sinensis (tea) is known for its therapeutic properties (anti-inflammatory, anti-microbial, anti-tumour, anti-oxidative and anti-ageing). Although, anti-microbial properties of green tea have been studied, its role against bacterial strains related to skin infections and mechanism of action is not well understood. We focussed on exploring anti-microbial activity and the basic mechanism of aqueous green tea leaf extract on selected bacterial strains. Staphylococcus epidermidis, Micrococcus luteus, Brevibacterium linens, Pseudomonas fluorescens and Bacillus subtilis were found to be sensitive to green tea extract via disc diffusion assay (zone of inhibition ≥7 mm). Minimal inhibitory concentration (MIC) was determined via nitro blue tetrazolium (NBT) assay (0.156-0.313 mg/ml). Moreover, the aqueous extract was found to be not toxic to the Vero cell-line up to a concentration of 500 μg/ml. The effect of aqueous extract on adhesion of different bacteria to Vero cells indicated that it inhibits the adhesion at its MIC value.     

脂肽和茶多酚对副溶血弧菌的协同抑菌效应和机理

研究脂肽和茶多酚对副溶血弧菌的协同抑菌效应和机理,为脂肽协同茶多酚应用于副溶血弧菌的控制提供理论依据。利用"棋盘法"研究脂肽和茶多酚对副溶血弧菌的协同抑菌效应;通过研究脂肽和茶多酚独立作用及协同作用对细胞膜完整性、细胞蛋白质合成及磷代谢方面影响来研究二者的协同抑菌机理。结果表明:脂肽和茶多酚对副溶血弧菌存在强烈的协同抑菌效应,部分抑菌浓度指数达到0.19;与1/16最小抑菌浓度(minimum inhibitory concentration,MIC)脂肽或1/8 MIC茶多酚各自独立作用相比,在1/16 MIC脂肽和1/8 MIC茶多酚协同作用下,副溶血弧菌的细胞膜通透性显著增强,细胞部分蛋白质合成的抑制作用得到进一步加强,并且细胞的磷代谢完全受到抑制。结果表明,脂肽和茶多酚对副溶血弧菌具有强烈的协同抑菌效应,其协同抑菌作用主要通过二者协同破坏细胞膜的完整性,从而影响细胞部分蛋白质的合成与正常代谢实现的。     

Antimicrobial activities of tea catechins and theaflavins and tea extracts against Bacillus cereus

We evaluated the antimicrobial activities of seven green tea catechins and four black tea theaflavins, generally referred to as flavonoids, as well as the aqueous extracts (infusions) of 36 commercial black, green, oolong, white, and herbal teas against Bacillus cereus (strain RM3190) incubated at 21 degrees C for 3, 15, 30, and 60 min. The results obtained demonstrate that (i) (-)-gallocatechin-3-gallate, (-)-epigallocatechin-3-gallate, (-)-catechin-3-gallate, (-)-epicatechin-3-gallate, theaflavin-3, 3'-digallate, theaflavin-3'-gallate, and theaflavin-3-gallate showed antimicrobial activities at nanomolar levels; (ii) most compounds were more active than were medicinal antibiotics, such as tetracycline or vancomycin, at comparable concentrations; (iii) the bactericidal activities of the teas could be accounted for by the levels of catechins and theaflavins as determined by high-pressure liquid chromatography; (iv) freshly prepared tea infusions were more active than day-old teas; and (v) tea catechins without gallate side chains, gallic acid and the alkaloids caffeine and theobromine also present in teas, and herbal (chamomile and peppermint) teas that contain no flavonoids are all inactive. These studies extend our knowledge about the antimicrobial effects of food ingredients.     

Antioxidant and antimicrobial performance of different Argentinean green tea varieties as affected by whey proteins

Green tea contains a high percentage of polyphenols, which are potent antioxidant and antimicrobial agents. However, interactions between polyphenols and food components may decrease their potential benefits. The aim of the study was to evaluate whether the antioxidant and antimicrobial capacities of different Argentinean green tea varieties could be affected by whey proteins. The results showed some degree of masking in the antioxidant and antimicrobial activity of green tea infusions when whey proteins are present. The degree of inhibition of antioxidant activity in each variety did not depend on the polyphenol concentration, indicating the importance of the particular polyphenol composition of each variety. The CH 410 variety exhibited the best performance as antioxidant and antimicrobial, even in the presence of whey proteins. The antimicrobial effects in the presence of whey proteins correlated with the polyphenol content of the green tea infusions and increased with the reduction of whey protein concentration. The antimicrobial effectiveness was similar within a pH range from 4.0 to 7.0, allowing its application to a wide group of foods.     

天然色素作为防腐剂的筛选及应用研究(一)

从姜黄、桔皮和花生衣等十二种植物中提取了天然色素，检测了它们的抑菌活性，提纯了其中三种，对其纯化前后的活性做了对比。结果表明：姜黄色素对多数细菌的抑制效果很好，最低抑菌浓度（MIC）为0．025g/ml；黄精色素对细菌和霉菌的MIC都是0．03g/ml；茶色素对大肠杆菌和金黄色葡萄球菌的MIC为0．025g/ml，对枯草杆菌的MIC为0．05g/ml；紫草色素对草霉有一定的抑制作用，MIC为0．05g/ml。经提纯后的姜黄色素具有抑菌效果，但不如姜黄原液。纯茶黄素和茶红素抑菌效果均比茶原液好，而精制后的紫草色素不再具有抑菌效果。