OBJECTIVETo investigate the effects of the chemical constituents of the whole herbs of Crossostephium chinense on insulin secretion in rat islets.

METHODIslets were isolated from rat pancreata, cultured in vitro, and measured by color signals of dithizone stained digestion solution for detection of pancreatic islets. The morphological observation of islets was carried out by inverted microscope. The effects of test compounds, scopoletin (1), scopolin (2), tanacetin (3), quercetagetin-3,6,7-trimethylether (4) and 5-O-methyl-myo-inositol (5) isolated from the whole herbs of C. chinense, on the insulin secreting level from islets were compared with those of glybenclamide as a positive control substances, and the difference in insulin secreting level from islets between the presence and absence of test compounds was assayed.

RESULTThere was no difference in basal insulin secretion before and after 2 h incubation period of rat islets. The islets treated with quercetagetin-3,6,7-trimethylether have about 2-fold higher insulin secreting level (P < 0.01) compared a normal control group. The islets treated with 5-O-methyl-myo-inositol have about 1.5-fold higher insulin secreting level (P < 0.05) compared to a normal control group. Whereas the islets treated with scopoletin show about 1.9-fold lower basal insulin secreting level (P < 0.05) than a normal control group.

CONCLUSIONIn this paper the developed cultivation method of isolated pancreatic islets from rat can be used as a kind of islet-based drug screening model for diabetes mellitus in vitro. Quercetagetin-3,6,7-trimethylether and 5-O-methyl-myo-inositol could enhance rat islet insulin secretion and further in vivo studies are needed to clarify the nature of such an observation. However, scopletin suppress rat islet insulin secretion.