Three new flavanoids from artificially induced dragon’s blood of Dracaena cambodiana

Three new flavanoids, (2R)-7,4′-dihydroxy-8-methylflavan (1), (2R)-7,4′-dihydroxy-6-methylflavan (2), and (3R)-7,3′,4′-trihydroxyhomoisoflavan (3), together with seven known compounds (4–10), were isolated from artificially induced dragon’s blood of Dracaena cambodiana, and their structures were determined based on HR-ESI-MS and extensive spectroscopic techniques (UV, IR, 1D-, and 2D-NMR). Compound 2 exhibited weak cytotoxicity against BEL-7402 cells line with the IC₅₀ value of 39.2 μM. In addition, compound 3 showed significant acetylcholinesterase (AChE) inhibitory activity.     

Root exudates drive interspecific facilitation by enhancing nodulation and N2 fixation

Plant diversity in experimental systems often enhances ecosystem productivity, but the mechanisms causing this overyielding are only partly understood. Intercropping faba beans (Vicia faba L.) and maize (Zea mays L.) result in overyielding and also, enhanced nodulation by faba beans. By using permeable and impermeable root barriers in a 2-y field experiment, we show that root–root interactions between faba bean and maize significantly increase both nodulation and symbiotic N₂ fixation in intercropped faba bean. Furthermore, root exudates from maize promote faba bean nodulation, whereas root exudates from wheat and barley do not. Thus, a decline of soil nitrate concentrations caused by intercropped cereals is not the sole mechanism for maize promoting faba bean nodulation. Intercropped maize also caused a twofold increase in exudation of flavonoids (signaling compounds for rhizobia) in the systems. Roots of faba bean treated with maize root exudates exhibited an immediate 11-fold increase in the expression of chalcone–flavanone isomerase (involved in flavonoid synthesis) gene together with a significantly increased expression of genes mediating nodulation and auxin response. After 35 d, faba beans treated with maize root exudate continued to show up-regulation of key nodulation genes, such as early nodulin 93 (ENOD93), and promoted nitrogen fixation. Our results reveal a mechanism for how intercropped maize promotes nitrogen fixation of faba bean, where maize root exudates promote flavonoid synthesis in faba bean, increase nodulation, and stimulate nitrogen fixation after enhanced gene expression. These results indicate facilitative root–root interactions and provide a mechanism for a positive relationship between species diversity and ecosystem productivity.Many ecosystems, including grasslands (1, 2), forests (3), phytoplankton communities (4), and cropping systems (5), show a positive relationship between plant diversity and ecosystem productivity. Several mechanisms have been proposed to explain this relationship. A “sampling effect” occurs, because more diverse mixtures have a higher probability of containing a species with higher productivity (6). Complementarity effects occur when species vary in resource use and niche differentiation in space or time, leading to greater resource utilization (6–9). Facilitation occurs when one species increases the growth of other species through a wide range of processes (10). Facilitative effects may be direct (e.g., by shade or protection from harsh conditions) or indirect (e.g., when one species reduces attack by pathogens or herbivores on other species) (11–13).Legume/cereal intercropping systems have been widely studied in the context of diversity and ecosystem function and commonly overyield, because dinitrogen (N₂) fixation by legumes increases ecosystem nitrogen (N) supply (7, 8), an example of facilitation. This facilitation is important to agriculture on a large scale, because application of chemical N fertilizer decreases biological N₂ fixation by legumes. Intercropping with maize increases N₂ fixation by faba bean, even with high input of N fertilizer (7), but such a stimulatory effect on faba bean has not been observed in all legume/cereal intercropping systems (7), suggesting species-specific facilitative relationships (14). Plants communicate by an “underground highway”—root exudates, which inhibit or facilitate their neighbors (15)—and part of this communication is through flavonoids, which are key signals in nodulation of legumes. How exactly maize promotes faba bean nodulation and the potential role of flavonoids remain unclear. Here, we explore cross-talk between maize and faba bean through rhizosphere processes and physiological and molecular mechanisms underpinning this communication.     

铁线莲属植物的化学成分研究进展

笔者对毛茛科铁线莲属植物化学成分研究进行了综述。铁线莲属植物化学成分比较复杂，化学结构类型包括三萜、黄酮、木脂素、香豆素、生物碱、挥发油、甾体、有机酸、大环化合物及酚类等，其中三萜皂苷、黄酮、木脂素是主要的结构类型。铁线莲属植物中的三萜皂苷主要为齐墩果酸型和常春藤皂苷元型，其中大部分为苷元的3位和28位均连有糖链的双糖链苷，只有少数为苷元的3位或28位接糖链的单糖链苷，有些皂苷的糖链上还有乙酰基(Ac)、咖啡酰基(CA)、异阿魏酰基(IF)、对甲氧基桂皮酰基(MC)和3，4-二甲氧基桂皮酰基(DMC)等取代基。其中的黄酮按结构类型可分为黄酮(苷)、黄酮醇(苷)、二氢黄酮(苷)、异黄酮(苷)和酮，既有氧糖苷，也有碳糖苷，其苷元主要为芹菜素、山柰酚、木犀草素和槲皮素。该属植物中的木脂素有Eupomtene型、环木脂素、单环氧木脂素、双环氧木脂素和木脂内酯。铁线莲属植物资源广泛，目前尚有必要进一步拓展其研究范围，以便更好地对其进行开发利用。     

淫羊藿黄酮对阿尔茨海默病小鼠模型学习记忆能力的影响

目的 观察淫羊藿黄酮对β-淀粉样肽(Aβ)拟阿尔茨海默病(AD)模型小鼠学习记忆能力的影响.方法 将ICR小鼠随机分为正常组、假手术组、模型组,淫羊藿黄酮小剂量(0.03 g/kg)、中剂量(0.1 g/kg)、大剂量(0.3 g/kg)组.灌胃给药14d后,行右侧脑室注射Aβ1-40造模,继续给药7 d,进行Morris水迷宫、避暗实验和自主活动实验,观察小鼠学习记忆能力.结果 Aβ1-40侧脑室注射模型小鼠出现学习记忆障碍.淫羊藿黄酮中、大剂量组在Moms水迷宫实验中逃避潜伏期[(40.12±4.15)s.(34.99±5.49)s]和游泳距离[(648.36±88.42)cm,(781.57±104.41)cm]明显缩短.与模型组逃避潜伏期(65.45±5.15)s,游泳距离(1142.66±96.80)em比较,差异具有显著性(P<0.01),在避暗实验中可延长模型小鼠的潜伏期[(255.40±11.00)s,(257.46±19.50)s]并降低其错误次数[(0.80±0.14)次,(0.77±0.17)次],与模型组潜伏期[(196.27±25.47)s],错误次数[(1.47±0.31)次]比较,差异有显著性(P<0.05).在自主活动实验中,各组之间差异无显著性(P>0.05).结论 淫羊藿黄酮能明显提高Aβ脑室注射致AD小鼠模型的学习记忆能力.     

淫羊藿黄酮对转基因痴呆小鼠脑内突触相关蛋白的影响

目的 观察10月龄APP转基因模型小鼠脑内突触相关蛋白--突触素(SYP)及突触后致密物质-95(PSD-95)蛋白表达的改变,以及中药有效部位淫羊藿黄酮对转基因小鼠脑内SYP和PSD-95表达的影响.方法 用药组小鼠自4月龄开始灌胃给予淫羊藿黄酮小剂量(0.03g·kg-1·d-1)、大剂量(0.1 g·kg-1·d-1)6个月至10月龄,正常对照组、转基因阴性对照组及模型组以同样方式灌胃给予蒸馏水.应用免疫组化及Western印迹方法分别检测海马CA1区、CA3区、齿状回及皮质中SYP的表达以及海马CA1区及皮质中PSD-95的表达.结果 与转基因阴性对照组相比,10月龄APP转基因模型小鼠皮质SYP蛋白表达明显较低(降低率为51.3%,P＜0.01);海马CA1区、CA3区及齿状回SYP阳性细胞的IOD值明显较低(降低率分别为59.1%、57.7%及56.5%,均P＜0.01).皮质PSD-95蛋白表达明显降低(降低率为36.4%,P＜0.01);海马CA1区PSD-95阳性细胞数少于对照组(减少率为18.5%,P＜0.05).灌胃给药6个月后,淫羊藿黄酮小、大剂量组小鼠皮质SYP蛋白表达明显高于模型组(增加率分别为40.0%,P＜0.05和106.4%,P＜0.01);海马CA1、CA3区及齿状回SYP阳性细胞IOD值均明显增加(均P＜0.01).淫羊藿黄酮小、大剂量组小鼠皮质PSD-95蛋白表达明显增加(增加率分别为57.3%,P＜0.05和84.3%,P＜0.01).淫羊藿黄酮大剂量组小鼠海马CA1区PSD-95阳性细胞数明显增加(增加率为22.5%,P＜0.05).结论 淫羊藿黄酮能通过促进突触相关蛋白表达而发挥维护神经元突触正常结构的作用,提示淫羊藿黄酮对改善AD神经元突触损伤状况具有潜在应用价值.     

黄酮类化合物对动物实验性肝损伤保护作用的研究进展

各种黄酮类化合物如黄酮类、黄酮醇类、二氢黄酮类、异黄酮类、黄烷酮类等对化学性肝损伤、药物性肝损伤、免疫性肝损伤、酒精性肝损伤、缺血/再灌注性肝损伤等实验性肝损伤均有不同程度的保护作用。这种保护作用与黄酮化合物清除自由基、抗氧化、抗脂质过氧化反应、调节免疫功能等有关。研究各种黄酮类化合物对动物实验性肝损伤的作用对于开发防治肝脏疾病的药物有重要意义。该文就近年来黄酮类化合物对动物实验性肝损伤作用的研究进展作一综述。     

CBN对小鼠耐缺氧作用的研究

目的：观察ＣＢＮ对于缺氧状态的影响。方法：通过常压耐缺氧、小鼠体内血栓形成和体外培养脑神经原等试验，对ＣＢＮ的作用进行观察。结果：１ＣＢＮ可以在一定程度上延长小鼠常压缺氧状态下的存活时间，１０ｍｇ／ｋｇ作用明显。２明显对抗由鼠脑凝血活素所致小鼠体内血栓形成所引起的死亡。３直接保护脑神经细胞，避免其因缺糖缺氧而引起的膜通透性改变。结论：ＣＢＮ可以提高小鼠常压缺氧和血栓性缺氧的耐受能力，并对脑神经原有明显的保护作用。     

瑞香狼毒中的黄酮类化合物

目的：研究瑞香狼毒Stellera chamaejasme根的化学成分。方法：采用硅胶柱层析分离,通过理化鉴定和波普分析确定是化学结构。结果;从瑞香狼毒根中分得4个黄酮类化合物,分别鉴定为新狼毒素甲（neochamaejas-minA,I)、表枇杷素（epiafzelechin,II)狼毒色原酮（chamaechromone,III)和芫花醇乙（wikstrolB,IV),结论;其中II和IV为首次从该植物中分得,同时还利用2DNMR修正了Niwa对化合物III的^13CNMR的归属。     

黄酮类化合物的药物代谢研究进展

黄酮类化合物是食物和传统中药中所含的一类重要的天然植物成分。大多数黄酮具有很强的还原活性故在体内易被氧化代谢,该过程通常由CYP1A酶家族参与。此外,某些甲氧基黄酮在体内还可进行脱甲基代谢;黄酮类化合物的分子结构中往往含有1个或多个酚羟基,易和葡萄糖醛酸、硫酸或谷胱甘肽等结合,生成水溶性较大的化合物排出体外;天然黄酮类化合物多以苷类形式存在,口服后易被肠道菌群产生的水解酶代谢为苷元再吸收入血。不少黄酮类化合物对CYP酶有较强的抑制作用,该作用是某些黄酮类化合物预防和抑制肿瘤的重要机制之一。该文总结了黄酮类化合物药物代谢的特点,并对黄酮类化合物和CYP酶的代谢相互作用进行了综述。     

The medicinal chemistry of tea

The medicinal effects of tea (Camellia sinensis) have a long, rich history. The first references to tea date back nearly 5,000 years and are justifiably obscure. Tea has been consumed literally for thousands of years, and it is this long safety record of tea consumption that makes these compounds an attractive target for drug discovery. Much attention has been focused on the role of tea flavanoids in the promotion of health in recent years. However, future studies will need to clarify further the mechanisms of action of these and related compounds, as well as their absorption, metabolism, and potential toxicity. We review here some of the currently available information pertaining to the chemistry, synthesis, pharmacokinetics, and pharmacodynamics of these compounds, which will hopefully serve as a starting point for the continued investigation of these compounds in the clinical setting. Drug Dev. Res. 61:45–65, 2004. © 2004 Wiley‐Liss, Inc.