Biol. Pharm. Bull. 29(7) 1418—1422 (2006)

sis MILLER (Aloe vera) is the most widely used. Aloe vera contain two major parts: firstly, leaves containing a high concentration of anthraquinone compounds that have been used throughout the centuries as a cathartic and for medicinal purges; and secondly, a clear gel that has been used as a food and to treat burns and other wounds. Several chemical components of the Aloe gel are thought to be responsible for its wound healing and immunostimulatory properties. For example, glycoprotein Aloectin A is reported to have anti-tumor and anti-ulcer effects, and a 29 kDa glycoprotein has been found to increase proliferation of normal human dermal cells. Most of these polysaccharides are glucomannans, mannans, or pectins with a range of molecular weights. A major focus of research has been on the carbohydrate fraction isolated from Aloe gel known as “acemannan,” which comprises a polydispersed b-(1,4)-linked acetylated mannan interspersed with O-acetyl groups. As a result of these studies, there have been numerous reports of Aloe having diverse biological activities, including anti-tumor activity, anti-acid activity, tyrosinase inhibiting activity, and antioxidant activity. Two clinical trials are available from the same research group that reported hyperglycemic effects on fasting blood glucose as well as on HbA1c levels with Aloe vera gel. Hikino et al. isolated two hyperglycemic polysaccharides from Aloe arborescens at 1985. Beppu et al. separated two different anti-diabetic components from the leaf pulp and leaf skin of the same plant. A previous study made with Kidachi Aloe (Aloe arborescens var. naralensis) in streptozotocin (STZ)-induced diabetic rats confirmed its efficacy through administration, contrary to Koo who reported hyperglycemic effects in diabetic rats in acute phase with a product containing Aloe vera gel. In this study, we sought to determine the constituents of Aloe vera gel extract that normalize hyperglycemia in the diabetic mouse strain BKS.Cg-m / Lepr (db/db), which exhibits many of the metabolic disturbances of human type 2 diabetes including hyperglycemia, obesity, and insulin resistance. Hemoglobin A1c (HbA1c), a binding product of glucose and hemoglobin, increases depending on the severity of hyperglycemia in a glucose level-dependent manner, and the level of HbA1c reflects the past blood glucose control conditions over a long period. Therefore, we tried to isolate the bioactive compounds from Aloe vera gel based on their ability to decrease the HbA1c level of db/db mice. Finally, we examined whether phytosterols and fractions isolated from Aloe vera gel play an important role in anti-hyperglycemic activity.