Structure-activity analysis on ecdysteroids: A structural and quantum chemical approach based on two biological systems

Besides their central role in the development of insects, ecdysteroids are widely found in other organisms as well. It is well established that ecdysteroids occur in various molecular forms as well as are valuable targets to identify structural requirements for the development of insecticides in favour of plant protection. Therefore, very advanced 3D- and 4D-QSAR have been applied to ecdysteroids. Our work, at present, is carried out by the arrangement use of quantum chemistry at semi-empirical level, molecular similarity measures and bio-statistical analysis. This strategy proficient gets into details of structure-activity of different ecdysteroid analogs. On the other hand, due to the analysis of a hormonal factor as multicellular scheme, in addition to the EC50 analysis in Drosophila melanogaster, the Calliphora test was taking into account. The influence of functional groups and different molecular properties (a total of 778) were cause-effect related to a set of 96 analogs for both tests. Additional theoretical analysis of hydrogen bonds and molecular orbitals were done as well. The work let to the achievement of a more realistic assessment in relation to the structure-activity, and it confirm that, geometrically, not all functional groups are important for bioactivity, only those whose contributions are involved in a quasi band of outer molecular orbitals. The discrimination of the most active molecules was done better by the use of the autosimilarity diagonal together with some other quantum and geometric variables.