The study of the electronic structure and conformation analysis were carried out on Brevetoxin and its analogs. Their active sites and the mode of action were determined, their structure-activity relationship and the interaction with receptors were discussed and the reason for the difference of activity between the analogs was given. It is found that the olefinic bond in the middle of molecule backbone, ring A and the olefinic bond in R are essential for the activity, and the bending of the molecular backbone has also effect on the activity. The study showes that the electron density of olefinic bond and the unoccupied orbitals indices of the olefinic bond as well as the molecular dipole moment correlate with the biological activity, respectively. The results show the electron structure has important effect on the activity. Moreover, the site of unsaturated ring in the middle of molecular backbone also has strong influence on the activity.

Key words: ELECTRONIC STRUCTURE, STRUCTURE ACTIVITY RELATIONSHIP, ACTIVITY, PHARMACOLOGY, MOLECULAR ORBITAL THEORY