| Morus alba Leaves is a traditional Chinese medicine, which contains many compounds including flavonoids, polysaccharides and alkaloids. It has a variety of bioactivities and clinical applications, which has been used in the treatment of diabetes, high blood pressure, and other diseases.1-deoxynojirimycin (DNJ), which is the representative of polyhydroxy alkaloids and the main hypoglycemic component in Morus alba Leaves, has drawn much attention of international scientists. However, so far, most of the research on Morus alba Leaves focus on the the study of hypoglycemic activity of Morus alba Leaves crude extract. The studies on the hypoglycemic activity of single pure components are seldomely repoeted, especially for those analogues of DNJ. In this paper, seven pure compounds were isolated from the water extract of Morus alba Leaves through economic and traditional ion exchange method. Then, the hypoglycemic activity of seven compounds were teated by a model in vitro, and the their possible hypoglycemic mechanism was investigated tentatively.1. A HPLC method was established for the analysis of 1-deoxynojirimycin and its analogues by using of a hydrophilic column and an evaporative laser scattering detector (ELSD). This method is more simple and faster than the derivative method and can be used for the qualitative and quantitative analysis of Morus alba Leaves sample effectively.2. The water extract of Morus alba Leaves, prepared under the assistance of ultrasound, was subjected to the repeatative ion exchange separation and the final Sephadex gel chromatography purification, seven pure compounds were obtained. Five of them were identified as 1-deoxynojirimycin, and its three analogues, 2-O-α-D-galactopyranosyl-1-deoxynojirimycin, fagomine, 1,4-dideoxy-1,4-imino- (2-O-β-D-glucopyranosyl)-D-arabinitol and myo-inositol. The structures of other two compounds need further elucidation.3. A hypoglycemic activity model in vitro was established for the test of of the hypoglycemic activities of seven derived pure compounds. The results indicated that six of them possed significant hypoglycemic activity. Among of them, 1-deoxynojirimycin showed the strongest hypoglycemic activity with the IC50 0.30μg/mL and 1.68μg/mL based on sucrose and maltose as the substrate respectively. Meantime, myo-inositol and 2-O-α-D-galactopyranosyl-1-deoxynojirimycin also showed a strong hypoglycemic activity with the IC50 similar to positive control acarbose. In addition, the type of DNJ inhibition of hypoglycemic activity was investigated by Lineweaver-Burk method, and the results showed that DNJ as aα-glucosidase inhibitor displayed a mixed competitive inhibition mechanism.4. The changes of the hypoglycemic activity of 26 different types of Morus alba Leaves with the different seasons were also examined in this paper. The results showed that the hypoglycemic activity of most type of Morus alba Leaves displayed a trend of decreasing from May (mulberry-picking season) to October (frost season) , and the highest hypoglycemic activity occurs in May. Meanwhile, among the 26 types of Morus alba Leaves, Nong 14, 306, 402, Jialing 16, Jialing 20 showed stronger hypoglycemic activity compared to others.The research results about hypoglycemic components and activities achived in this paper can provide a good direction for the further studies and exploration of hypoglycemic effect of Morus alba Leaves. |
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