Photoreactivity of drugs is at the basis of phenomena of large relevance to applications. Drug photostability is an issue of practical concern. Biological photosensitization reactions may represent undesired side effects in therapy or be at the basis of specific therapeutic approaches (es. photodynamic therapy with porphyrins). These reactions rely on intermediates and products, generated by light absorption by drug chromophores, which, upon interaction with cellular components, lead to cell degeneration and/or death. In situ photoactivation of drugs is an emerging research area that may open the way to an extension of related applications. Understanding the photoreactivity of drug chromophores, isolated or complexed to biological molecules, is therefore a prerequisite for control of the pharmacological activity/toxicity of drugs. In this context some photorections of interest for applications and/or modelling are currently studied in solution and in complexes with cyclodextrin nanocarriers, proteins and DNA: the photodehalogenation of fluoroquinolones, the photodecarboxylation of arylpropionic acids and the photoinduced processes occurring in anthracycline derivatives. A further cathegory of drugs under attention is that of the antimalarials, due to the need of finding new compounds to which resistance of the parasite has not yet been developed. Among these, we are studying the Artemisinin derivatives, obtained by semi-synthesis of a natural compound. Circular Dichroism spectroscopy, Molecular Mechanics and Molecular Dynamics calculations and confocal fluorescence microscopy are applied with the aim of understanding the complicate mechanism of the drug action at molecular and cellular level.

Updated(18/06/2009)