Phytochemical Studies on Medicinally Important Plants

众所周知，植物能够产生一系列具有重要生物活性的次生代谢物。植物生物勘探是指从丰富的植物资源中寻找具有经济价值的生物化学资源。基于民族医学知识的生物勘探为药物开发计划提供了发现先导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。酶是人类生命所必需的，介导生物化学过程，包括代谢、细胞信号转导、细胞循环和发育。这些生化系统的故障常常导致疾病，这些疾病可由相关酶的功能障碍、过度表达或过度激活引起。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，降胆固醇剂洛伐他汀抑制酶(3S)-羟甲基戊二酰辅酶a （HMG-CoA）还原酶的活性，该酶催化HMG-CoA还原为甲羟戊酸盐，这是胆固醇生物合成的关键步骤。拟议的研究涉及药用重要植物的化学调查，以确定使其具有活性的主要生物活性化合物（如生物碱、萜类、香豆素、类固醇和类黄酮等）。我们从加拿大和南非的草原省份收集了几种植物，这些植物是基于传统治疗师治疗各种疾病的民族医学用途。这些植物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、抗恶性疟原虫烯酰acp还原酶（ppfenr）、抗结核分枝杆菌烯酰acp还原酶（MtENR）和抗肾素。据报道，所有这些酶（AChE、α -葡萄糖苷酶、GST、ppfenr、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/心脏病的发病机制。本研究不仅验证了传统治疗师对药用植物的民族医学用途，而且有助于确定天然产物作为新的候选药物分子，抑制上述健康问题发病机制中涉及的酶作为其分子靶点。在此授权期内，我们将开展该研究计划的四个主要目标：(i)利用生物测定指导的植物化学研究对药用重要植物进行铅生物活性天然产物的分离和表征；（ii）鉴定内生真菌作为强效生物活性天然产物的替代来源；（iii）对生物活性化合物进行结构修饰，以研究其构效关系（SAR）；（iv）化学酶法合成生物活性化合物。该跨学科研究整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HPLC， NMR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。在进行这项研究的过程中，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、化学和制药行业。这项发现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.