This volume contains nine more contributions from expert researchers of the ?eld, providing readers with in depth and current research results regarding therespective topics. In the ?rst chapter, Flemming et al. review the chemistry, biosynthesis, metabolism and biological activities of tetrahydrocannabinol and its deri- tives. Hansch and Verma contribute to the quantitative structure-activity re- tionship (QSAR) analysis of heterocyclic topoisomerase I and II inhibitors. These inhibitors,knowntoinhibit either enzyme, actasantitumoragentsand are currently used in chemotherapy and in clinicaltrials. In the third chapter, Khan reviews some aspects of molecular modeling studies on biologically active alkaloids, brie?y providing considerations on themodeling approaches. In next chapter, Khan and Ather review different aspects of the microbial transformationsof theimportant nitrogenousmolecules, as they have diverse biological activities. This chapter provides a critical update of the microbial transformations reported in recent years, targeting novel biocatalysts from microbes. In the ?fth chapter, Hamdi and Dixneuf describe the synthesis of triazoles andcoumarins molecules andtheirphysiologicalactivities. Maiti and Kumar, in their contribution, review the physicochemical and nucleic acid binding properties of several isoquinoline alkaloids (berberine, palmatine and coralyne) and their derivatives under various environmental conditions. Inchapterseven,Berlinckdescribesvarietiesofpolycyclicdiaminealkaloids such as halicyclamines, 'upenamide, xestospongins, araguspongines, hali- clamines, haliclonacyclamines, arenosclerins, ingenamines and the mad- gamines, etc.,and their synthesis as well as biologicalactivities.