Stability study of a α-methylene-γ-butyrolactone issued from lichens

Protolichesterinic acid (PLA) 1 and lichesterinic acid (LA) 2, isolated from lichens are described to have anti-inflammatory, anti-tumor and anti bacterial properties. LA can be readily obtained from PLA through isomerization thus raising the question of stability of the latter. So we studied the stability of 1 under different conditions of solvent, temperature and time. Solvents were chosen for their ability to improve the solubility of 1 which is low in aqueous media, thus of negative incidence in biological testing. Concentrations were determined by HPLC coupled with a photodiode array detector. The calibration curves have been established from synthesized products. In a second time, compound 3 was synthezised and submitted to temperature and solvent conditions, determined by the above study, to elucidate the role of the carboxylic function.