Antidiabetic properties of selected Mexican copalchis of the Rubiaceae family.

The extracts prepared from the stem barks of several Mexican copalchis species, including Hintonia latiflora, Exostema caribaeum and a commercial mixture of Hintonia standleyana and E. caribaeum (CM) showed significant hypoglycemic and antihyperglycemic effects. The extracts were tested in three different in vivo models using normal and streptozotocin (STZ)-induced diabetic rats. From the active extract of H. latiflora, 25-O-acetyl-3-O-beta-D-glucopyranosyl-23,24-dihydrocucurbitacin F (1), an analog of 23,24-dihydrocucurbitacin F, and several known compounds (2-8) were isolated; cucurbitacin 1 was also isolated from H. standleyana. Oral administration of H. latiflora extract [100mg/kg of body weight (bw)] and 5-O-beta-D-glucopyranosyl-7,3',4'-trihydroxy-4-phenylcoumarin (5) (30 mg/kg of bw) to STZ-induced diabetic rats, for a 30 day duration, restored blood glucose levels to normal values. The groups treated either with the active principle 5, or the extract of H. latiflora, showed less body weight loss than glibenclamide-treated and diabetic control groups (p<0.05). It was also demonstrated that the extract of H. latiflora regulated hepatic glycogen and plasma insulin levels (p<0.05). These data suggest that its antihyperglycemic effect is due in part to stimulation of insulin secretion and regulation of hepatic glycogen metabolism.