Ikechukwu Ogbonna J, Ifeanyi Ofoefule S
Department of Pharmaceutical Technology and Industrial Pharmacy, Faculty of Pharmaceutical Sciences, University of Nigeria, Nsukka, Nigeria.
Recent Pat Antiinfect Drug Discov. 2016;11(1):44-52. doi: 10.2174/1574891x11666151105130233.
Allium cepa has been in use in traditional medicine in the treatment of diabetes mellitus. The aqueous and ethanolic extracts have been found effective in lowering blood glucose levels in experimental diabetic rats and guinea pigs.
The study was carried out to isolate the active principle responsible for the observed hypoglycaemic effect in experimental animals. Freeze-dried aqueous extract of Allium cepa was separated into various fractions using column chromatography with silica gel as a stationary phase. The column was eluted with various ratios of mixtures of hexane, chloroform, ethyl acetate and methanol. These column fractions obtained were tested for hypoglycaemic effects in alloxan-induced diabetic male rats. The identified active fraction was further separated by means of preparative thin layer chromatography (P-TLC) using silica gel as stationary phase and mixture of solvents chloroform, ethyl acetate, and methanol in the ratio of 10: 4: 1 respectively as the mobile phase. Pre-coated P-TLC plates were used and the fraction bands were identified under u.v. lamp and by spraying with concentrated sulphuric acidvanillin reagent. The isolated bands (Rf 0.438) were scrapped off from the P-TLC plates, redissolved in absolute methanol, filtered and concentrated to dryness.
The isolated compound's structure was determined be means of one and two dimensional nuclear magnetic resonance spectroscopy as well as comparison with literature data. The isolated compound given at 25 mg/kg dose reduced blood glucose in diabetic rats in manner which was comparable to the effect obtained with 2 mg/kg of glibenclamide (p < 0.05). The structure of the compound was found to be that of kaempferol- 3-O-β - D 6{P-coumaroyl} glucopyranoside.
The research findings have supported the claims that extracts of Allium cepa possess glucose lowering properties in experimental diabetic animals.
洋葱已被用于传统医学中治疗糖尿病。已发现其水提取物和乙醇提取物对实验性糖尿病大鼠和豚鼠具有降低血糖水平的作用。
本研究旨在分离出在实验动物中观察到的降血糖作用的活性成分。以硅胶为固定相，采用柱色谱法将洋葱冻干水提取物分离成不同组分。用己烷、氯仿、乙酸乙酯和甲醇的不同比例混合溶液洗脱柱子。对所获得的这些柱分离组分在四氧嘧啶诱导的糖尿病雄性大鼠中进行降血糖作用测试。通过制备薄层色谱法（P-TLC）进一步分离鉴定出的活性组分，以硅胶为固定相，分别以10:4:1比例的氯仿、乙酸乙酯和甲醇混合溶剂为流动相。使用预制的P-TLC板，在紫外灯下并通过喷洒浓硫酸香草醛试剂来鉴定组分条带。从P-TLC板上刮下分离出的条带（比移值0.438），用无水甲醇重新溶解，过滤并浓缩至干。
通过一维和二维核磁共振光谱法以及与文献数据比较确定了分离出的化合物的结构。以25mg/kg剂量给予分离出的化合物可降低糖尿病大鼠的血糖，其效果与给予2mg/kg格列本脲所获得的效果相当（p<0.05）。发现该化合物的结构为山奈酚-3-O-β-D-6-{对香豆酰基}吡喃葡萄糖苷。
研究结果支持了洋葱提取物在实验性糖尿病动物中具有降血糖特性的说法。
