liver cells and in CB-treated cells alterations in the appearance and location of microfilaments were observed. Furthermore, it was found that CB reversibly inhibits melanin granule movement in melanocytes. One year later, research on the influence of cytochalasin B on chloroplasts was done. It was found that the light-oriented movement of chloroplasts is reversibly inhibited by cytochalasin B. In 1973 researches found that cytochalasin B is a powerful non-competitive inhibitor of glucose transport. One of the major electrophoretic identifiable erythrocyte membrane proteins may be the cytochalasin B binding site of erythrocytes. From 1980 In the following years, the knowledge concerning cytochalasin B was broadened. As the more general knowledge had been elucidated, more detailed analysis of e.g. the mechanism of action took place. Production Cytochalasins can be isolated from the fungi in which they naturally occur. Originally, they were isolated from Helminthosporium dematioideum. Other producers include Phoma spp., Hormiscium spp. and Curvularia lunata. Additionally, it can be synthesized in the laboratory. There are several approaches to do so. Firstly, it is possible to form the six-membered ring of the isoindolone core and the larger macrocyclic ring simultaneously in a late-stage intramolecular Diels-Alder cyclization. Secondly, it is possible to first form the isoindolone core in an intermolecular Diels-Alder reaction and in a second step append the macrocycle in a stepwise fashion. Properties Cytochalasin B contains several highly polar keto- and hydroxyl groups and one peripheric lipophilic benzyl unit. Mechanism It is suggested that the predominant mechanism of cytochalasin B is the inhibition of actin filament polymerization through binding to the fast-growing (barbed) end of F-actin filaments. An alternative could involve capping proteins. By doing so, CB not only inhibits actin polymerization but also consecutive processes such as filament network build-up. This inhibition can affect all three major steps of actin polymerization Nucleation: A core of minimal 3 actin monomers is formed. Elongation: The core is used for elongation by addition of actin monomers. Steady state/Annealing: A balance between polymerisation and depolymerisation is reached (steady-state). The F-actin filament stops growing and two barbed ends fuse to create one filament. Nucleation is essential for filament build-up. The oligomerization is the rate-determining step, considering actin filament formation as a whole. The so-called lag phase of actin polymerization originates from this step. It takes quite a while until polymerization starts, but once it has, the process is autocatalytic until the physiological maximum of the polymerization