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Abstract
PURPOSE:
The changes in molecular structure and the physiological properties of a gamma-irradiated aloe-emodin were examined.

MATERIALS AND METHODS:
Aloe-emodin was gamma-irradiated at doses ranging from 0 to 150 kGy, and the molecular structure was then analyzed using high-performance liquid chromatography (HPLC). AGS cells were cultured in RPMI medium and treated gamma irradiated aloe-emodin. Cell viability was measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Apoptosis efficiency was investigated by cell cycle arrest, cell morphology, and signaling pathway. The structure of new radiolytic peak was identified by the hydrogen-nuclear magnetic resonance (1H NMR).

RESULTS:
HPLC results showed that gamma irradiation induced new radiolytic peaks that were distinguishable from the aloe-emodin standard, and the area of new peaks was increased as the radiation dose increased. Gamma-irradiated aloe-emodin treatment significantly increased the cytotoxicity in AGS tumor cells. We also found that 150 kGy aloe-emodin increased the expression of Bax, cytosolic cytochrome c, PARP cleavage, and the activation of caspases-8, -9, -3, Bid, and Bcl-2. Treatment of 150 kGy aloe-emodin induced ROS production, DNA fragmentation, alterations of cell morphology, and the migration in AGS cells. Gamma-irradiated aloe-emodin induced an increase of sub-G1 phase and depolarization of mitochondrial membrane potential in AGS cells. We also confirmed that fractionated AEF1 (new radiolytic peak) induce the cell death, migration, an increase of sub-G1 phase and cytochrome c in a ROS-dependent manner.

CONCLUSIONS:
The radiolysis product (AEF1) of aloe-emodin transformed by gamma-irradiation strongly induced apoptotic cell death in AGS cells, indicating AEF1 is a potential candidate drug for use in anti-cancer drug.

Author information

Byun EB1, Kim HM1,2, Sung NY3, Yang MS4, Kim WS1, Choi D1, Mushtaq S1, Lee SS1, Byun EH3.
1
a Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute , Jeongeup , Korea.
2
b Department of Food and Biotechnology , Korea University , Sejong , Republic of Korea.
3
c Department of Food Science and Technology , Kongju National University , Yesan , Republic of Korea.
4
d Department of Microbiology, Infection Signaling Network Research Center, College of Medicine , Chungnam National University , Daejeon , Republic of Korea.