Excited-State Hydroxide Ion Release From a Series of Acridinol Photobases.

The excited-state heterolysis of acridinol-based derivatives leads to the release of the OH- ion and the formation of the corresponding acridinium cations. To evaluate the parameters that control the reaction barriers, the kinetics of excited-state OH- release from a series of acridinol photobases were studied using transient absorption spectroscopy. The rate constants were obtained in three solvents (methanol, butanol, and isobutanol), and the data were modeled using Marcus theory. The intrinsic reorganization energies obtained from these fits were found to correlate well with the solvent reorganization energies calculated using dielectric continuum model, suggesting that the excited-state OH- release occurs along the solvent reaction coordinate. Furthermore, the ability of acridinol photobases to photoinitiate chemical reactions was demonstrated using the Michael reaction between dimethylmalonate and nitrostyrene.

Polyhydroxyalkanoate-based 3-hydroxyoctanoic acid and its derivatives as a platform of bioactive compounds.

A library of 18 different compounds was synthesized starting from (R)-3-hydroxyoctanoic acid which is derived from the bacterial polymer polyhydroxyalkanoate (PHA). Ten derivatives, including halo and unsaturated methyl and benzyl esters, were synthesized and characterized for the first time. Given that (R)-3-hydroxyalkanoic acids are known to have biological activity, the new compounds were evaluated for antimicrobial activity and in vitro antiproliferative effect with mammalian cell lines. The presence of the carboxylic group was essential for the antimicrobial activity, with minimal inhibitory concentrations against a panel of bacteria (Gram-positive and Gram-negative) and fungi (Candida albicans and Microsporum gypseum) in the range 2.8-7.0 mM and 0.1-6.3 mM, respectively. 3-Halogenated octanoic acids exhibited the ability to inhibit C. albicans hyphae formation. In addition, (R)-3-hydroxyoctanoic and (E)-oct-2-enoic acids inhibited quorum sensing-regulated pyocyanin production in the opportunistic pathogen Pseudomonas aeruginosa PAO1. Generally, derivatives did not inhibit mammalian cell proliferation even at 3-mM concentrations, while only (E)-oct-2-enoic and 3-oxooctanoic acid had IC50 values of 1.7 and 1.6 mM with the human lung fibroblast cell line.