Characterization of anticholinesterase-active 3-alkylpyridinium polymers from the marine sponge Reniera sarai in aqueous solutions

From the marine sponge Reniera sarai 3-alkylpyridinium oligomers and polymers have been isolated. 3-Alkylpyridinium polymers are potent anticholinesterase agents; in addition, they show hemolytic and cytotoxic activities. Oligomers with a molecular weight lower than 3000 Da do not possess any significant activity. We report structural characterization of 3-alkyl-pyridinium polymers and their behavior in aqueous solutions. We found that biologically active polymers are composed of head-to-tail 3-alkylpyridinium units. According to MALDI-TOF spectrometry two species of polymers exist, the smaller with a molecular weight of 5520 Da and the larger with a molecular weight of 18 900 Da. Both polymers are soluble only in water, while low molecular oligomers are readily soluble in organic solvents. Polymers form large water-dissolved supramolecular structures with an average hydrodynamic radius of 23 ( 2 nm and, therefore, cannot be separated with size-exclusion chromatography. Recently, several 3-alkylpyridinium compounds en-dowed with potent biological activities have been iso-lated from various marine sponges. These compounds have been described as constituted of 3-alkylpyridiniu