Photodynamic therapy (PDT) is a light activated chemotherapy that is dependent on three parameters: photosensitizer (PS) concentration; oxygen concentration; and light dosage. Due to highly variable treatment response, the development of an accurate dosimeter to optimize PDT treatment outcome is an important requirement for practical applications. Singlet oxygen is an active species in PDT, and...

Mangostin (MAG), a kind of xanthone widely used in diet and medicine, has antioxidant, anti-inflammatory, antimicrobial, and anticancer activities. On account of its antioxidant activity, MAG might protect cancer cells from free radical damage in photodynamic therapy (PDT) during which reactive oxygen species production was stimulated leading to irreversible tumor cell injury. In this study, th...

In a great many cases the participation of singlet oxygen in sensitized photooxigenation processes in solution has been stated Singlet oxygen has sometimes also been assumed to be the important intermediate in photodynamic reactions2. Unfortunatly in most instances a direct proof by spectroscopic methods is practically impossible because of its low emission quantum yield in solution. Therefore ...

Plants are often exposed to external conditions that adversely affect their growth, development or productivity. Such unfavourable environmental stress factors may result in rapid and transient increases of intracellular concentrations of reactive oxygen species (ROS) that are chemically distinct and impact plants either by being cytotoxic or by acting as a signal. Because different ROS are gen...

p38 mitogen-activated protein kinase is activated and involved in cleavage of caspase-3 during apoptosis induced by a number of stimuli. However, the signaling events triggered by p38 that result in caspase-3 activation are still unknown. In human leukemia cells, two reactive oxygen species, singlet oxygen and hydrogen peroxide (H(2)O(2)), selectively stimulated the phosphorylation of p38. Prei...

The generation of hydroxyl radicals and singlet oxygen during the oxidation of 4-(4-hydroxyphenyl)-2-butanol (rhododendrol) and 4-(3,4-dihydroxyphenyl)-2-butanol (rhododendrol-catechol) with mushroom tyrosinase in a phosphate buffer (pH 7.4) was examined as the model for the reactive oxygen species generation via the two rhododendrol compounds in melanocytes. The reaction was performed in the p...