Phytochemical Studies on Medicinally Important Plants

植物产生的次生代谢物种类繁多，具有重要的生物活性。植物的生物勘探需要从丰富的植物中寻找有经济价值的生化资源。以民族医学知识为基础的生物勘探为药物开发提供了发现铅生物活性化合物的可能性。药物发现过程的一个方面是鉴定具有酶抑制活性的小分子。酶是人类生命中必不可少的物质，参与新陈代谢、细胞信号转导、细胞周期和发育等生化过程。这些生化系统的故障通常会导致疾病，这些疾病可能是由相关酶的功能障碍、过度表达或过度激活引起的。在分子水平上对疾病的理解为临床提供了几种酶抑制剂。例如，降胆固醇药洛伐他汀抑制了酶(3S)-羟甲基戊二酰辅酶A(HMG-CoA)还原酶的活性，该酶催化HMG-CoA还原为甲羟戊酸，这是胆固醇生物合成的关键步骤。拟议的研究涉及对具有重要药用价值的植物进行化学调查，以确定铅的生物活性化合物(如生物碱、萜类、香豆素、类固醇和黄酮类等)(S)。这使它们变得活跃起来。我们从加拿大和南非的草原省份收集了几种植物，基于传统治疗师对它们治疗各种疾病的民族医学用途。这些植物的粗甲醇提取物具有多种酶抑制活性，包括抗乙酰胆碱酯酶(AChE)、抗谷胱甘肽转移酶(GST)、抗α-葡萄糖苷酶、抗恶性疟原虫Enoyl-ACP还原酶(PfENR)、抗结核分枝杆菌Enoyl-ACP还原酶(MtENR)和抗肾素活性。据报道，所有这些酶(AChE、α-葡萄糖苷酶、GST、PfENR、MtENR和肾素)分别参与阿尔茨海默病/帕金森病、糖尿病或改善抗癌/抗寄生虫化疗、疟疾、结核病和高血压/心脏问题的发病机制。这项研究不仅将验证传统医家对药用植物的民族医用，而且有助于将天然产物确定为新的候选药物分子，作为其分子靶点，抑制参与上述健康问题发病机制的酶。在这一授权期内，我们将实现这项研究计划的四个主要目标：(I)利用以生物测定为指导的重要药用植物的植物化学研究来分离和表征铅的生物活性天然产物；(Ii)确定内生真菌作为有效生物活性天然产物的替代来源；(Iii)生物活性化合物的结构修饰，以研究其构效关系(SAR)；以及(Iv)化学-酶法合成生物活性化合物。这项跨学科的研究融合了先进的化学仪器方法(用于纯化和鉴定生物活性化合物的高效液相、核磁共振和LC-MS/GC-MS光谱技术)、微生物反应、合成有机化学、计算化学、生物化学和微生物学。在进行这项研究时，本科生和研究生将被培养成加拿大许多机构的未来科学家，包括生物技术、食品、化工和制药行业。这一发现基金的成功完成将提供新的生物活性化合物，以揭示其未知的生物合成途径和药效团，并为合成有机化学家设计新的合成策略提供具有挑战性的目标。

Plants are known to produce a wide array of secondary metabolites which possess valuable bioactivities. Bioprospecting of plants entails the search for economically valuable biochemical resources from the floral wealth. Bioprospecting based on ethnomedical knowledge holds out the possibility for discovering lead bioactive compounds for drug discovery program. One of the aspects of drug discovery process is the identification of small molecules with enzyme-inhibiting activities. Enzymes are essential to human life, mediating biochemical processes including metabolism, cellular signal transduction, cell cycling, and development. Malfunction in these biochemical systems often leads to disease that can be caused by the dysfunction, overexpression, or hyperactivation of the enzymes involved. An understanding of diseases at the molecular level has provided several enzyme inhibitors in clinics. For instance, lovastatin, a cholesterol-lowering agent, inhibits the activity of enzyme (3S)-hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase that catalyzes the reduction of HMG-CoA to mevalonate, a key step in cholesterol biosynthesis. The proposed research involves the chemical investigation of medicinally important plants in order to identify the lead bioactive compound(s) (e.g. alkaloids, terpenoids, coumarins, steroids and flavonoids etc.) that makes them active.We have collected several plants from the Prairie Provinces of Canada and South Africa based on their ethnomedical uses by traditional healers to treat various ailments. The crude methanolic extracts of these plants exhibited various enzyme inhibitory activities including anti-acetylcholinesterase (AChE), anti-glutathioneS-transferase (GST), anti-alpha-glucosidase, anti-Plasmodium falciparum Enoyl-ACP reductase (PfENR), anti-Mycobacterium tuberculosis Enoyl-ACP reductase (MtENR) and anti-renin activities. All of these enzymes (AChE, alpha-glucosidase, GST, PfENR, MtENR and renin) are reported to be involved in the pathogenesis of Alzheimer's disease/Parkinson's disease, diabetic or improving of anti-cancer/anti-parasitic chemotherapy, malaria, TB and hypertension/cardiac problems, respectively. This research will not only validate the ethnomedical use of medicinal plants by traditional healers but also helps to identify the natural products as new candidate drugs molecule that inhibit the enzymes, involved in the pathogenesis of aforementioned health problems, as their molecular target. During this granting period, we will be carrying out four major objectives of this research program: (i) isolation and characterization of lead bioactive natural products using bioassay-directed phytochemical studies on medicinally important plants; (ii) identification of endophytic fungi as an alternative source of potent bioactive natural products; (iii) structural modifications of bioactive compounds in order to study their structure-activity relationships (SAR); and (iv) chemo-enzymatic synthesis of bioactive compounds. This interdisciplinary research integrates advanced chemical instrumentation methods (HPLC, NMR and LC-MS/GC-MS spectroscopic techniques for the purification and identification of bioactive compounds), microbial reactions, synthetic organic chemistry, computational chemistry, biochemistry and microbiology. In carrying out this research, undergraduate and graduate students will be trained as future scientists for many Canadian institutions including the biotechnological, food, chemical and pharmaceutical industries. The successful completion of this discovery grant will provide new bioactive compounds to reveal their unknown biosynthetic pathways and pharmacophores as well as to provide challenging targets to synthetic organic chemists in designing new synthetic strategies.