Enhancement of the antiviral activity of pyrimidine derivatives against mengovirus by visible light.

Eleven pyrimido-pyrimidine derivatives, seven with significant antiviral activity against Mengovirus, five against Coxsackie B1 virus and four antiviral negative compounds were tested for their photosensitizing ability. All seven compounds with antiviral activity in vitro showed an enhanced antiviral action against Mengovirus under irradiation with visible light, a fact that may be caused by photodynamic processes. It was tried to correlate the oxidation potentials of sensitizers with their photodynamic activity. By means of mass-spectrometric investigations, molecular fragmentation was examined following thin layer chromatography (TCL) before and after irradiation. Furthermore, binding affinity to biopolymers (BSA and RNA) was investigated to reveal conformity in differences of antiviral activity. The main results are the following: 1. Generally, strong antiviral activity can be correlated with strong binding affinity. 2. No significant correlation could be detected between oxidation potentials of antiviral compounds and their enhanced antiviral activity under irradiation conditions, although in some cases sensitizer with higher oxidation potentials are more effective than those with lower ones. 3. The lower the photostability of the compounds the higher was the light-induced antiviral activity. 4. No alteration of the molecular ion peak and fragmentation pattern before and after irradiation was indicated by means of mass-spectrometry and TLC using fairly comparable conditions.