Anti-diabetic activity-guided screening of aqueous-ethanol Moringa oleifera   extracts and fractions: Identification of marker compounds

Purpose: To explore the anti-diabetic effects of Moringa oleifera extracts and fractions, and to identify their active/marker compounds.
Methods: Five different aqueous ethanol extracts (95, 75, 50, 25 %v/v and 100 % water) of Moringa oleifera were given orally to normal rats to assess their hypoglycemic activities and effect on intraperitoneal glucose tolerance test (IPGTT) data. Rats with streptozotocin-induced diabetes were used to assess acute and sub-chronic anti-hyperglycemic activities. The most active extract was further subjected to liquid-liquid fractionation into hexane, chloroform, ethyl acetate, butanol, and water; these fractions were screened for anti-diabetic activities. The most active extract, and fractions thereof, were then subjected to qualitative and quantitative phytochemical analysis. Standardization was achieved via thin layer chromatography (TLC) and high-performance liquid chromatography (HPLC), and used to identify marker compounds.
Results: Of all the extracts and fractions, 95 % (v/v) ethanol extract (at 1,000 mg/kg) and the butanol fraction thereof (at 500 mg/kg) were the most active, reducing blood glucose concentration after one-time (acute) administration to diabetic rats (p < 0.01). No significant hypoglycemic activity was apparent, and the materials had no effect on IPGTT performance by normal rats. TLC and HPLC identified quercetin 3-β-D-glucoside, kaempferol-3-O-glucoside, and cryptochlorogenic acid.
Conclusion: An M. oleifera leaf extract exhibited anti-hyperglycaemic activity in diabetic rats only. This effect was likely attributable to cryptochlorogenic acid, quercetin 3-β-D-glucoside, and kaempferol 3-O-glucoside.

Keywords
Anti-diabetic; Moringa oleifera; Cryptochlorogenic acid; Quercetin; 3-β-D-glucoside; Kaempferol 3-O-glucoside; Streptozotocin