Singlet oxygen (1O2), a reactive oxygen species, has been found to be implicated in many cellular events and pathological disorders. Herein, we investigated the reactivity of 1O2 towards the anaesthetic agent propofol (PPF) encapsulated within DMPC liposomes. By time resolved luminescence, the rate constant of 1O2 quenching by PPF was evaluated, depending on the location of the sensitizer, with following values: 1.35+/-0.05x10(7) M(-1) s(-1) for deuteroporphyrin (as embedded source) and 0.8+/-0.04x10(7) M(-1) s(-1) for uroporphyrin (as external source), respectively. The nature of the oxidation product, resulting from the reaction of 1O2 with PPF, was determined using absorption and HPLC techniques. Finally, the in vitro protective effect of PPF towards the 1O2-induced neuronal cell toxicity was evaluated in terms of cell viability.