D-(+)-MANNOSE is used as an osmolyte and transport facilitator in a variety of biological in vivo and in vitro applications, such as improvement of blood-brain barrier transport and hyperosmolar therapy. D-Mannitol is used as a substrate to identify, differentiate and characterized enzymes such as mannitol dehydrogenase(s). D-Mannitol is used in identify mannitol metabolizing bacteria and used in sweetness inhibition studies.