Many drugs approved for marketing between 2003 and 2012 owe their existence to natural product leads discovered from mainly actinomycete, bacteria and fungal sources. It has been our intention with this book to not only provide insights into the likely sources and methodologies that may be used to discover new natural product based drugs in the future, but also to stress the utility and importance of this approach to drug discovery in terms of new clinical candidates and recent commercial successes. This book contains judicious combination of both spectral and chemical techniques used for structure elucidation of unknown compounds. Further, the book provides a balanced view of various biological activities that are frequently carried out in natural product chemistry. Therefore this book can hopefully benefit various postgraduate students through out the world.