Antioxidant activity of mangostin in cell-free system and its effect on K562 leukemia cell line in photodynamic therapy.

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, the antioxidant activity of MAG was investigated and the influence of MAG on K562 cells in 5-aminolevulinic acid (ALA)-based PDT is demonstrated. The results showed that MAG could scavenge hydroxyl radical, superoxide anion, and hydrogen peroxide and inhibit the formation of malondialdehyde (MDA), but increase the amounts of singlet oxygen in cell-free systems. MAG inhibits cell proliferation and enhances cell apoptosis, lipid peroxidation, and DNA damage in ALA-PDT on K562 cells. NaN3, a singlet oxygen quencher, suppresses the MAG-induced cell apoptosis, lipid peroxidation, and DNA damage. In conclusion, MAG enhances the PDT-induced cytotoxicity in K562 cells and singlet oxygen was involved in this process. These results implied that the effect of antioxidants on PDT might be determined by its sensitization ability to singlet oxygen.

Ultrastructure and cytochemical localization of acid phosphatase of laticifers in Euphorbia kansui Liou.

Acid phosphatase (AcPase) activities are involved in the degeneration process of cytoplasm in plants. In this study, acid phosphatase was detected by the method of lead nitrate and cytochemical electron microscopy during the development of nonarticulated laticifers in Euphorbia kansui Liou. The most important feature in the differentiation of the laticifers in E. kansui is that the development of small vacuoles arises from endoplasmic reticulum (ER). The mature laticifers possess a thin layer of electron-dense peripheral cytoplasm in which the organelle cannot be distinguished and a large central vacuole filled with latex particles. AcPase cytochemistry studies show AcPase reaction products congregated into heaps are distributed along the tonoplast of central vacuole and around the mitochondria and plastids. Some small vacuoles which develop at later developmental stages of laticifers contain AcPase reaction products. As a result, the central vacuole is formed by cellular autophagy and fusion of small vacuoles which apparently arises from ER.