| Swertia kouitchensis Franch.(Gentianaceae) has long been used as a folk medicine to treat hepatitis and diabetes in central-western China. Therefore, this study was aimed to evaluate the anti-diabetic activity of the plant extract, and also the chemical components related with its anti-diabetic activity.Chapter I In vitro and in vivo anti-diabetic activity of Swertia kouitchensis extractFirstly, the extract was tested for its inhibitory activity on a-amylase and a-glucosidase in vitro. Following that, insulin secretion test in NIT-1cell was performed. Then, oral sucrose or starch tolerance test of the extract were carried out in normal mice. After that, acute effect of the extract was executed in normal and streptozotocin-induced (60mg/kg) diabetic mice. Eventually, long term effect of the extract was performed in diabetic mice for4weeks. Oral glucose tolerance test and biochemical parameters were estimated at the end of the study.It turned out that S. kouitchensis extract could remarkably inhibit the activity of a-amylase and a-glucosidase and stimulate insulin secretion in vitro. And also the extract displayed anti-hyperglycemic activity, improved antioxidant capacity, ameliorated the hyperlipidemia and carbohydrate metabolism in diabetic mice. These results provide a rationale for the use of S. kouitchensis to treat diabetes mellitus.Chapter II Chemical investigation of Swertia kouitchensisAs a continuous search for anti-diabetic compounds from S. kouitchensis, especially the anti-a-glucosidase activity, our investigation on S.kouitchensis led to the isolation and elucidation of63compounds as the following: kouitchenoid A-B (1-2), kouitchensone (3), kouitchenside A-K (4-14), tetrahydro-kouitchenside A-C (15-17), β-sitosterol (18), oleanolic acid (19), ursolic acid (20), sweriaperenine (21),1-hydroxy-3,7-dimethoxy xanthone (22), Methylbellidifolin (23),1-hydroxy-3,5-dimethoxy xanthone (24), bellidifolin (25), isobellidifolin (26),1-hydroxy-3,5,8-trimethoxy xanthone (27), norbellidifolin (28),1,7-dihydroxy-3,4,8-trimethoxy xanthone (29), Corymbiferin (30),1,3-dihydroxy-4,5-dimethoxy xanthone (31), Veratrilogenin (32), Daphnifolin (33),1,3,7-trihydroxy-4-methoxy xanthone (34), Gentianin (35), Isoswertianin (36),1,3-dihyroxy-5-methoxy xanthone (37),1,8-dihydroxy-3,4,5-trimethoxy xanthone (38), Decussatin (39),1-hydroxy-3,5,7,8-tetramethoxy xanthone (40),(5R,8S)-tetrahydroswertianolin (41),(5R,8S)-Campestroside (42),1-O-(β-D-xylopyranosyl-(1-6)-β-D-glucopyranosyl)-3,5-dimethoxy xanthone (43),1-O-Primeverosyl-3,7,8-trimethoxy xanthone (44),1-0-(β-D-glucopyranosyl-(1-6)-β-D-glucopyranosyl)-8-hydroxy-3,7-dimethoxy xanthone (45), Triptexanthoside D (46), Swertianolin (47), Norswertianolin (48), Mangiferin (49), Neolancerin (50),7-0-[a-L-rhamnopyranosyl-(1-2)-β-D-xylopyr-anosyl]-1,8-dihydroxy-3-methoxy xanthone (51),7-0-[β-D-xylopyranosyl-(1-6)-β-D-glucopyranosyl]-1,8-dihydroxy-3-methoxy xanthone (52),1-O-(β-D-xylopyranosyl-(1-6)-β-D-glucopyranosyl)-8-hydroxy-3,7-dimethoxy xanthone (53),7-0-[a-L-rhamnopyranosyl-(1-6)-β-D-glucopyranosyl]-5,3’-dihydroxy-4’-methoxy flavanol (54),6-C-glucopyranosyl]-5,7,3’,4’-tetrahydroxy flavone (55),3-0-[a-L-rhamnopyranosyl-(1-6)-β-D-galacopyranosyl]-5,7,3’,4’-tetrahydroxy flavone (56),6-C-glucopyranosyl-5,7,4’-trihydroxy flavone (57),3-O-[α-L-rhamnopyranosyl-(1-6)-β-D-galacopyranosyl]-5,7,4’-trihydroxy flavone (58),3-0-[a-L-rhamnopyranosyl-(1-6)-β-D-glucopyranosyl]-5,7,4’-trihydroxy flavone (59),6-C-glucopyranosyl-5,7,4’-trihydroxy-3’-methoxy flavone (60), swertiamarin (61), erythrocentaurine (62), swertiaside A (63). Aong them, compounds1-17were new ones, and compounds (22-23,26-27,30-38,40-46,48-63) were isolated from S. kouitchensis for the first time. The isolated compounds were evaluated for their a-glucosidase inhibitory activity in vitro. The results indicated that compounds5,6,7,12,47,49,53(IC50in the range of126to451μM) displayed more inhibitory effect on a-glucosidase than the reference drug acarbose (IC50627μM) did. |
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