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Microbial Transformations of Sclareol

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Microbial Transformations of Sclareol Studies on the Chemical Constituents of Pleurolzs Species and Buxus hyrcøna; Microbial Transformations of Sclareol By ZAHEER UDDIN BABAR A Thesis Submitted to the Faculty of Graduate Studies ln Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Department of Chemistry University of Manitoba Winnipeg, Manitoba, Canada 2005 O Copyright by Zaheer Babar STUDIES ON THE CHEMICAL CONSTITUENTS OF PLEUROTUS SPECIES AND BUXUS HYRCANA; MICROBIAL TRANSFORMATIONS OF SCLAREOL BY ZAHEER UDDIN BABAR A Thesis submitted to the Faculty of Graduate Studies of the University of Manitoba in the partial fulfillment of the requirements of the degree of MASTER OF SCIENCE 02005 Permission has been granted to the LIBRARY OF TIIE UNMRSITY OF MANITOBA to lend or sell copies of this thesis, to the NATIONAL LIBRARY OF CANADA to microfitm this thesis and to lend or sell copies of the film, and LIBRARY MICROFILMS to publish an abstract of this thesis. The author reserves other publication rights, and neither the thesis nor extensive extracts from it may be printed or other-rvise reproduced without the author's written permission This thesis is dedicated to my family TABLE OF CONTENTS Page Abstract Acknowledgments vi CHAPTER 1 General Introduction 1 CHAPTER 2 Chemical Studies on Pleurotus Species 2.0 Introduction l7 2.1 Results and Discussion 27 2.2 Experimental JJ 2.3 References 36 CIIAPTER 3 Phytochemical studies on Buxus hyrcønø 39 3.0 Introduction 39 3.1 Results and Discussion 43 3.2 Experimental 49 3.3 References 50 CHAPTER 4 Microbial Transformations of Sclareol 52 4.0 Introduction 54 4.2 Results and Discussion 59 4.3 Experimental 67 4.4 References 7T CONCLUSIONS 74 v Abstract This thesis describes chemical studies on the methanolic-ethyl acetate extract of Pleurotus species and Buxus hyrcana, and the microbial transformation of sclareol. Chemical studies on Pleurotus sp. resulted in the isolation of a steroid known as ergosterol peroxide (53). This compound (53) exhibited weak antibacterial activity against Bacíllus subtilis, Staphylococcus aureus and Corynebacterìum xerosis. Phytochemical investigations on the methanolic extract of the Buxus hyrcana have resulted in the isolation of a novel triterpenoidal alkaloid, Oó-buxadiene (6a). This compound (64) showed weak anticancer activity against prostate cancer cell lines (LNCaP). The second part of this thesis describes the microbial transformation of sclareol (78\, a plant natural product. Two fungi Curvularía lunata (ATCC 12017) and Mucor plumbeus (ATCC 4740) were capable of oxidizing sclareol into 3B-hydroxysclareol (79) and 18o-hydroxysclareol (80) by standard two stage fermentation method. Antibacterial assay showed that the oxidation products (79) and (80) were less bioactive than sclareol (78). This indicated that antibacterial activity was lost due to the presence of a hydroxyl group at 3B and l8crin (79) and (80), respectively. Their structures were established mainly on the basis of mass, IR, UV, lD and2D NMR spectroscopic studies. VI Acknorvledgments This thesis would not have been possible without the guidance of Dr. Athar Ata. I extend my sincere gratitude to him for allowing me the opportunity to pursue graduate research under his supervision, and to benefit from his knowledge of chemistry. I would like to thank Mr. Ed Segestro and Mr.Terry Wolowiec for their help with the GC/MS and NMR, respectively. I owe my sincere gratitude to Dr. Paul Holloway for his help with the antibacterial studies. I wish to thank Dr. M. H. Meshkatalsadat, Department of Chemistry University of Lorestan, Iran, for supplying us with the crude extract of Buxus hyrcana. I would also like to thank the members of the Department of Chemistry at the University of Manitoba, and The University of Winnipeg, especially the academic, technical and administrative staff,, for their support. I do greatly appreciate to all those who participated in funding the research on which this thesis is based. Finally, I am forever indebted to my mother and my family for their endless patience and encouragement when these were rnost required. CHAPTER 1 NATURAL PRODUCTS Natural products are organic compounds derived from marine organisms, plants, microorganisms, and insects. These naturally occurring organic compounds are used as flavoring agents, spices, cosmetics, pharmaceutical and biological agents. It is reported in the literature that about 80o/o of the world's population rely on traditional medicines for primary health.l Citations for the use of nafural substances as medicines can be found as far as 78 4.D., when Dioscorides wrote "De Materia Medica", describing the use of thousands of plants as ingredients in crude drug preparations. He further added that these plants serve as the sources of pure chemicals which might be responsible for pharmaceutical activity.2 There have been several waves of interest in pharmacognosy or natural products chemistry. The research activity in this area is stronger now than perhaps at any other time. This could be attributed to several factors, including unmet therapeutic needs; the remarkable diversity of both chemical structures and biological activities of secondary metabolites; the utilify of novel bioactive natural products as biochemical probes; the development of novel and sensitive techniques to detect biologically active natural products; improved techniques to isolate, purify, and charactenzethe active constifuents; and advances in solving the demand for supply of complex natural products. Natural products have served as a valuable source of molecular diversity in many drug discovery programs, and several important drugs have been isolated. The medicinal agents such as quinine (1), theophylline (2), morphine (3), cyclosporine A (4), and vitamin A (5) are the foundation of modern pharmaceuticar "are.t o lt "ra-*-\a-*¡t "^^.Å/I H:C CH: CH¡ O (2',) CH¡ N olcH" ll H/t HlllN\*ì19.", cH¡ o (4) CH¡ \s cH2oH In drug discovery program, bioassay-guided isolation technique plays an important role in the isolation of the new bioactive compound(s). Some of these compounds have been reported to have novel carbon skeletons. Known natural products are also targeted because of their pharmaceutical activity. For instance, betulinic acid (6), one of the most potent anti-HIV agents known, was isolated from syzigium clavíflorum.a HsC Over the past 25 years, it has been well documented that most of the drugs available in the market are of natural product origin. For instan ce 50%o of the pharmacy based prescription products are natural product-derived entities and half of them are derived from plants.s The approved and regulated chemical armamentarium available today is failing to provide effective health care for even one-third of the human population. Additionally, known therapeutic agents are reported to exhibit resistance to several diseases including cancer, malaria, tuberculosis and other infectious diseases.6 These days discovery efforts aim at the identification of new therapeutic regimens, but not at the problem to overcome the development of resistance to the already existing therapeutic agents. 1.1 IMPORTANT NATURAL PRODUCT-DERIVED PHARMACEUTICALS The use of plant and animal products to control disease has been well documented for centuries, the biochemical basis for observed efficacies did not come 4 under careful scientific scrutiny until the 18th and lgth centuies, particularly in the early to mid 1800's when a number of important, pharmacologically active natural products such as the cardiac glycosides and a variety of bioactive alkaloids, ê.g., atropine (7), strychnine (8) and colchicine (9) were discovered. cH20H o (8) oYt"' r) ...NH r) H (10) (e) Many of these biologically active natural products became important not only for their use directly as therapeutic agents or as prototype lead compounds for the development of new drugs, but also as biochemical probes to unravel the principles of human pharmacology, a role for natural products which continues today. Based on the need of health care, pharmaceuticals are classified into the following classes: 1.1.1 CardiovascularDrugs 1.1.2 Central Nervous System Drugs 1 .1.3 Anti-infectives 1.1.4 Anticancer Drugs f .i.5 Immunomodulators 1.1.1 Cardiovascular Drugs Increasing the force of contraction of the heart (positive inotropic activity) is very important for most heart failure patients. Cardiac glycosides including digoxin (ll), ( 11) digitoxin (12), and deslanoside (13), exerr a powerful and selective positive inotropic action on the cardiac muscle. (12 ) 6 (13) A number of naturally occurring alkaloidal drugs are also being used in the control of various cardiovascular conditions. For instance ergotamine (14), an ergot alkaloid obtained from a fungus that infects rye grass, is an important central vasoconstrictor and is used therapeutically to treat migraine headaches. N 7 The new long-acting ergoline derivative cabergoline (15), launched as an antiprolactin, one of the dopamine D2 receptor agonists, is also being evaluated as a potential therapy for Parkinson's disease and as an anticancer agent for the treatment of breast cancer.T (tt' NH ( 1", N--------.,..- N--cH¡ Most of the cholesterol lowering drugs are derived from fungi. They act by inhibition of 3-hydroxy-3-methylglutaryl coenzyrne A reductase (HMG-CoA reductase), an enzqe critical in the biosynthesis of cholesterol. For example, Lovastatin (16), isolated from the fungus Aspergillus terreus inhibits 3-hydroxy-3-methylglutaryl coenzyme A.8 CH¡ lrrgt"' ( 16) 8 1.1,.2 Central Nervous System Drugs A number of natural products have been reported to exhibit central nervous system (CNS) activity. Examples include, d-tubocurarine (17), a neuromuscular blocker which was isolated from the South American plant, Curare.3 The opium alkaloids, codeine and morphine (3), served as models for the synthesis of naloxone (18), an important analog used to treat and diagnose opiate addicts.e ..sH t\.",N Hrcrd N (18) Hrct" ocH3 (r7) (+)-Epibatidine (19), isolated from the skin of the poisonous frog, exhibits exceptional analgesic activity and is a very potent nicotinic acetylcholine receptor (nAChR) agonist.
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