A combination of photoelectron spectroscopy and quantum-chemical calculations is used to resolve electronic structure of small natural products and its effect on their physiological activity. New algorithm for selection of most important variables in regression models will be tested and compared with alternative selection methods. Possibility to optimize topological indexes is investigated. One research program is dedicated to derive novel complex compounds with specific structural and biological properties. A series of new organometalic complexes with alkali and transition metal ions is prepared and characterized in an effort to provide new antitumor and antiviral drugs.