D-Xylose

Xylose is a sugar first isolated from wood. Xylose is classified as a monosaccharide of the aldopentose type, which means that it contains five carbon atoms and includes an aldehyde functional group. It is derived from hemicellulose, one of the main constituents of biomass. Like most sugars, it can adopt several structures depending on conditions. Reduction of xylose by catalytic hydrogenation produces the sugar substitute xylitol. With its free aldehyde group, it is a reducing sugar. Xylose is the main building block for the hemicellulose xylan, which comprises about 30% of some plants (birch for example). Xylose is otherwise pervasive, being found in the embryos of most edible plants.

Xylose is also found in some species of beetles. Xylose is metabolised by humans, although it is not a major human nutrient. It is also used to test for malabsorption by administration in water to the animal after fasting.