Identification and Isolation of Secondary Metabolites from Podocarpus neriifolius Using Bioactivity-Guided and 1D-NMR-Based Dereplication Approaches Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Paule Annécie Benatrehina Graduate Program in Pharmaceutical Sciences The Ohio State University 2018 Dissertation Committee A. Douglas Kinghorn, Advisor Liva Harinantenaina Rakotondraive, Co-Advisor James R. Fuchs 1 Copyrighted by Paule Annécie Benatrehina 2018 2 Abstract In a continued effort aimed at the discovery of potential new anticancer leads of natural origin, a root sample of Podocarpus neriifolius D. Don, collected in the Vietnam rainforest, was selected as a candidate species for phytochemical and biological investigation of its bioactive secondary metabolites. An initial small-scale bioactivity- guided isolation of this plant sample was conducted, and yielded one new (83) and four known podolactones (77-79, and 84) together with three totarane-type diterpenes (80-82), with a structural revision carried out on 79. A larger scale extraction of the remaining sample was performed to isolate a greater amount of 83 for its complete structural characterization, as well as to investigate additional secondary metabolites from this plant. A 1D-NMR spectroscopy-guided fractionation method using both 1H and selective 1D- TOCSY NMR spectroscopy was developed as a dereplication procedure in the screening of the extracts and their fractions. This method led to the detection and isolation of further known compounds (85-92) from the hexanes, EtOAc, and aqueous extracts of P. neriifolius root sample, in addition to that of the targeted compound (83). Moreover, the 1H NMR profile of the aqueous extract revealed the presence of a major compound (89), corresponding to the glucoside derivative of the cytotoxic 78, and this compound by means of its extract of origin, was subjected to fungal-assisted biotransformation procedures using ii two Penicillium strains, namely, P. concentricum and P. expansum. A previously reported hydrolysis of compound 89 under harsh chemical conditions led to the A-ring epoxide unit opening of this compound, resulting in an inactive product. The fungal biotransformation proved to be a useful method for the successful hydrolysis of 89 to form 78, and the present study is the first report of a podolactone chemical modification in fungal fermentation cultures. The progress of the biotransformation reaction was monitored periodically using the newly developed 1D-NMR spectroscopic dereplication method, from which both the starting material (89) and product (78) were identified. The obtained isolates were evaluated for their antiproliferative activities against four human cancer cell lines, namely, HT-29 (colon), MDA-MB-231 (breast), MDA-MB-435 (melanoma), and OVCAR3 (ovarian). In addition, the bioactive and highly abundant inumakilactone A (78) was further evaluated in vivo in a murine xenograft model through a hollow fiber assay. Only compounds 78 and 79 were active against the cell lines used, while 78 did not show significant activity in vivo. Both 78 and 89 were tested in an insect anti-feedant assay, but neither were active. This dissertation study has opened new avenues for the dereplication in natural product discovery, as well as an additional method for the derivatization of the podolactones, using the 1D-NMR spectroscopic and fungal biotransformation experiments mentioned above, respectively. Finally, although the major compound, 78, did not exhibit in vivo activity against the human cancer subtypes tested, this information constitutes a new contribution to the published literature regarding the podolactone class of compounds. iii Dedication This dissertation is dedicated to both my late father, Telon Jacques Benatrehina (1951- 2008), and my grandmother, Monique Tombo (1940-2017), and to my family, mentors and teachers. iv Acknowledgments Achieving the work described in this dissertation and fulfilling all the prerequisites toward the completion of this doctoral degree have required significant effort, time, and most importantly significant support of various nature, including academic, research, professional, administrative, and personal, from a number of individuals. I would like to include a few words to acknowledge the various parties involved in making this journey a possibility and a success. First and foremost, I express my deepest gratitude to both my advisors, Prof. A. Douglas Kinghorn, and Dr. L. Harinantenaina Rakotondraibe, for the tremendous support and understanding they have provided me over the course of my graduate career. Prof. Kinghorn graciously welcomed me into his research group, and through the years he has entrusted me with various responsibilities within and outside the laboratory, notably as an assistant in the Journal of Natural Products office, all of which have greatly contributed to my scientific and professional growth. I also thank him for his continuous assistance and endorsement for my professional endeavors, including fellowship applications and conference participation. Dr. Rakotondraibe is to be thanked for willingly assuming the role of my co-advisor, and as such for patiently providing me with assistance and direction through my research projects with hands-on coaching and constructive criticism. v Moreover, I thank him for continuously encouraging me to keep challenging myself and think critically, while stimulating self-confidence. Both Prof. Kinghorn and Dr. Rakotondraibe have been and continue to be exemplary role models of hard work, integrity, patience and mentorship, making the success of their students a main priority. I would like to also thank Dr. James R. Fuchs, for his contribution as the third member on both my candidacy and dissertation committee. I am grateful for his valuable advice and constructive feedback regarding my research projects. Additionally, I thank Dr. Esperanza J. Carcache de Blanco for also being part of my candidacy committee. I thank the College of Pharmacy Graduate Research Committee and the Division of Medicinal Chemistry and Pharmacognosy, first for my admission into this graduate program, and for the administrative and professional support through career services, workshops and funding opportunities such as the Jack L. Beal and Chang Ahn travel awards, of which I have been privileged to be a recipient. I am also grateful for the many support services offered by The Ohio State University and from which I have greatly benefited, including professional and academic opportunities and coaching through the OSU Career and Counseling Service. The U.S. National Cancer Institute, NIH, Bethesda, MD is acknowledged for providing funding for this dissertation research through a program project grant P01 CA125066 awarded to Prof. A. D. Kinghorn as the principal investigator. The interdisciplinary nature of the work presented in this dissertation would not have been feasible without the involvement of many devoted collaborators, to whom I am indebted. vi Thus, I would like to acknowledge the valuable contribution of colleagues at the University of Illinois at Chicago (UIC) College of Pharmacy, namely, Dr. Djaja D. Soejarto for leading field collection of plant material, Dr. Joanna E. Burdette, Dr. Wei-Lun Chen, Mr. Austin Czarnecki, and Mr. Daniel Lantvit, for conducting the biological evaluation data. I thank Dr. Xiaoli Zhang (OSU) for providing her biostatistics expertise on the in vivo bioassay data. Moreover, I thank Dr. Craig McElroy for providing access, training and assistance for the use of various instruments within the College of Pharmacy, as well as Drs. Arpad Somogyi and Chunhua Yuan of the OSU Campus Chemical Instrument Center (CCIC) for assistance in acquiring mass spectrometry and NMR spectroscopy data, respectively. I am thankful for the many colleagues from various laboratories within the College of Pharmacy, including my fellow graduate students, many of whom I now consider good friends, for their help and support, making the challenges of the graduate program more manageable. First, I thank former and current members of the Kinghorn group, namely Drs. Patrick C. Still, Lynette Bueno Perez, and Yulin Ren, as well as Ms. Andrea L. Rague, Ms. Garima Agarwal, Mr. Ermias Mekuria Addo, and Mr. Peter J. Blanco-Carcache. Furthermore, I am grateful to Drs. Hee-Byung Chai, Li Pan, Jie Li, and C. Benjamin Naman, for being great research mentors, and for providing bioassay data (H.-B. Chai). I also thank former and current colleagues from the Rakotondraibe group, namely, Drs. Tehane Ali and Masanori Inagaki, Mr. Preston Manwill, and Mr. Choon Yong Tan and Ms. Fengrui Wang who have conducted biological testing for part of the dissertation vii project. In addition, I thank Mrs. Nicole Woodard from the Carcache de Blanco group, as well as Drs. Pratiq Patel and John Woodard, and Ms. Chido Hambira from the Fuchs group. I am grateful to Mrs. Alice Gardner and Mrs. Jennifer Bartlett, of the College of Pharmacy for their professional assistance and friendship over the years. I would also like to acknowledge the many mentors from my alma mater, Lipscomb University, including Drs. Jim Thomas, Kent Gallaher, Kent Clinger, and Susan Mercer, who have encouraged me to pursue graduate study in natural products research. I am mostly grateful to my family and friends near and far, who have been a great source of encouragement in this long journey.