title: Antihyperglycemic effect of orthosiphon stamineus benth leaves extract and its bioassay-guided fractions.
abstract: Preliminary investigations were carried out to evaluate the antidiabetic effects of the leaves of O. stamineus extracted serially with solvents of increasing polarity (petroleum ether, chloroform, methanol and water); bioassay-guided purification of plant extracts using the subcutaneous glucose tolerance test (SbGTT) was also carried out. Only the chloroform extract, given at 1 g/kg body weight (b.w.), significantly reduced (P < 0.05) the blood glucose level of rats loaded subcutaneously with 150 mg/kg (b.w.) glucose. The active chloroform extract of O. stamineus was separated into five fractions using a dry flash column chromatography method. Out of the five fractions tested, only chloroform fraction 2 (Cƒ2), at the dose of 1 g/kg (b.w.) significantly inhibited (P < 0.05) blood glucose levels in SbGTT. Active Cƒ2 was split into two sub-fractions Cƒ2-A and Cƒ2-B, using a dry flash column chromatography method. The activities Cƒ2-A and Cƒ2-B were investigated using SbGTT, and the active sub-fraction was then further studied for anti-diabetic effects in a streptozotocin-induced diabetic rat model. The results clearly indicate that Cƒ2-B fraction exhibited a blood glucose lowering effect in fasted treated normal rats after glucose-loading of 150 mg/kg (b.w.). In the acute streptozotocin-induced diabetic rat model, Cƒ2-B did not exhibit a hypoglycemic effect on blood glucose levels up to 7 hours after treatment. Thus, it appears that Cƒ2-B functions similarly to metformin, which has no hypoglycemic effect but demonstrates an antihyperglycemic effect only in normogycemic models. The effect of Cƒ2-B may have no direct stimulatory effects on insulin secretion or on blood glucose levels in diabetic animal models. Verification of the active compound(s) within the active fraction (Cƒ2-B) indicated the presence of terpenoids and, flavonoids, including sinensitin.
authors.affiliation: School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800, Penang, Malaysia. aliali692002@yahoo.com
authors.forename: Elsnoussi Ali Hussin
authors.initials: EA
authors.lastname: Mohamed
authors.forename: Ali Jimale
authors.initials: AJ
authors.lastname: Mohamed
authors.forename: Mohd Zaini
authors.initials: MZ
authors.lastname: Asmawi
authors.forename: Amirin
authors.initials: A
authors.lastname: Sadikun
authors.forename: Omar Saad
authors.initials: OS
authors.lastname: Ebrika
authors.forename: Mun Fei
authors.initials: MF
authors.lastname: Yam
mesh_terms: D000818:Animals; D002855:Chromatography, Thin Layer; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy; D005260:Female; D007004:Hypoglycemic Agents / Q000737:chemistry* / Q000627:therapeutic use*; D031342:Orthosiphon / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry* / Q000627:therapeutic use*; D018515:Plant Leaves / Q000737:chemistry*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D007004:Hypoglycemic Agents; D010936:Plant Extracts