The anti-oxidative activity of the rare sugar D-allose has recently been reported, but the mechanism is largely unclear. In this study, we evaluated the reactive oxygen species (ROS) scavenging activities of D-allose and then examined the effects of D-allose on ROS production in mitochondria to clarify the antioxidant properties of D-allose. While D-allose did not scavenge hydrogen peroxide and superoxide anions, it eliminated hydroxyl radicals to the same extent as D-glucose. Rotenone, an uncoupler of mitochondrial respiratory complex I, induces ROS production in mouse neuroblastoma Neuro2A cells in the presence of D-glucose. However, in the presence of D-allose, there was no change in the ROS levels in Neuro2A cells following rotenone treatment. Furthermore, treatment with D-allose attenuated the D-glucose-dependent ROS generation induced by rotenone. Whereas treatment with D-glucose enhanced ATP synthesis in Neuro2A cells, D-allose was less effective in producing intracellular ATP than is-glucose. Treatment with D-allose inhibited the ATP synthesis stimulated by D-glucose. These results suggest that D-allose suppresses ROS production in the mitochondria due to competition with D-glucose at the cellular level. (C) 2011, The Society for Biotechnology, Japan. All rights reserved.