Quebrachitol (QCT), a bioactive plant constituent, is a naturally occurring optically active cyclitols. QCT could serve as the starting material of inositol or its derivatives to participate in several important pathways and may act as a potential anticancer or antidiabetic drug lead to arrest or reverse these diseases. According to the literature reported before, QCT exerted its biological functions, by involving IP3 receptor, b-glucosidase, PAFR, COX2, nitric oxide synthase, and K(+)ATP channels. Quebrachitol reduces the gastric damage induced by ethanol and indomethacin. The potential of quebrachitol as a sugar substitute for diabetics has been investigated. Even though the early study reported that this methylcyclitol seems neither to prevent hypoglycemia nor to raise blood sugar content, another work showed that quebrachitol has hypoglycemic effects in hyperglycemic rats. Unfortunately, all three persons who took quebrachitol by mouth had fairly severe diarrhea.