Identification of five phytosterols from Aloe vera gel as anti-diabetic compounds.
The genus Aloe in the family Liliaceae is a group of plants including Aloe vera (Aloe barbadensis MILLER) and Aloe arborescens (Aloe arborescens MILLER var. natalensis BERGER) that are empirically known to have various medical efficacies. In the present study, we evaluated the anti-hyperglycemic effect of Aloe vera gel and isolated a number of compounds from the gel. On the basis of spectroscopic data, these compounds were identified as lophenol, 24-methyl-lophenol, 24-ethyl-lophenol, cycloartanol, and 24-methylene-cycloartanol. These five phytosterols were evaluated for their anti-hyperglycemic effects in type 2 diabetic BKS.Cg-m(+/+)Lepr(db/J) (db/db) mice. In comparison with the hemoglobin A1c (HbA1c) levels of vehicle-treated mice, statistically significant decreases of 15 to 18% in HbA1c levels were observed in mice treated with 1 mug of the five phytosterols. Considering the ability to reduce blood glucose in vivo, there were no differences between the five phytosterols. Administration of beta-sitosterol did not reduce the blood glucose levels in db/db mice. After administration of the five phytosterols for 28 d, fasting blood glucose levels decreased to approximately 64%, 28%, 47%, 51%, and 55% of control levels, respectively. Severe diabetic mice treated with phytosterols derived from Aloe vera gel did not suffer weight reduction due to glucose loss in the urine. These findings suggest that Aloe vera gel and phytosterols derived from Aloe vera gel have a long-term blood glucose level control effect and would be useful for the treatment of type 2 diabetes mellitus.